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Electrical problems can be terribly difficult to diagnose properly. Electrical and fuel-related problems manifest themselves in the same ways: hard starting, mis-firing, poor performance, back-firing, etc.

Although the electrical systems on XJ bikes are fairly durable, there are a number of known, common problem areas on these bikes, which are compounded by the fact that these bikes are 25+ years old.

The fusebox is the most critical area: the stock one may have been adequate in 1981, but it's now old, outdated, and ready for the dust-bin of history. We carry replacement ATC-style fuseboxes and in-line fuse holders which allow you to easily upgrade your original.

The generator brushes wear down over time, change their electrical characteristics as they age, and need periodic replacement. They are available as complete brushes with holder assemblies, or brushes only. By the way, in a technical sense, your bike is really equipped with an Alternator, not a Generator (as Yamaha calls it), since the output of that electrical-generating device is an alternating (AC) electrical current, which is then rectified into a direct (DC) current via---you guessed it---the rectifier section of your Regulator box......

Anyway: finally, in a general electrical system sense, the wiring harness on your bike is getting old---and like most vehicle wiring harnesses from this era, they aren't (and never were) the most robust things ever made. Corrosion, weak connectors, and other assorted issues will cause you all sorts of headaches and the agony of electrical troubleshooting nightmares if not addressed and remedied.

An exceptional write-up on the electrical system on XJ-series bikes---the good, the bad, and the ugly---can be found at:


I highly recommend that you visit that site and PRINT OUT the FAQ (you never know when a web page might disappear from the web), as it is the "Electrical Bible" for XJ owners!

And understanding the importance of (and how to measure) voltage drops in circuits will go a long way to helping you successfully diagnose and solve electrical problems on your bike:


and here’’s an easy-to-understand guide to how to perform a voltage-drop test:


And finally, if you want to become much more of an expert on your electrical system, we recommend this excellent site……although it was written by/for owners of the Yamaha Vision series of bikes, all of the basic information and some of the bike-specific information is also applicable to the XJ model bikes. Easy to understand, and easy to learn from, the ideas and concepts explained here can really help you become comfortable enough to perform many diagnostics and repairs to the electrical system on your bike.


A nice consolidated "cheat sheet" covering many of the electrical components on your bike can be found at:




And a great companion write-up on these subjects and some basic ignition system trouble-shooting guidelines can be found at:


And a very good review of the issue of electrical resistance in ignition systems can be found at:


Although the above article references the ignition systems in ultra-light aircraft, the same concepts apply to all ignition systems.

And Testing 101 may be a good summary for you to review, before you rip all your hair (and wiring) out:


A multi-meter is one of the mandatory tools that you must have and know how to use:






MiCarl's wiring diagrams: note that some of these diagrams are for Euro bikes, which may be a bit different than North American bikes. Also beware: factory wire diagrams do have errors in them.


Here’s a good source of info on how to actually read a wiring schematic:


Another good source for wiring diagrams can be found at:

NOTE: some of these may be for non-US models.

1981-3 XJ550 Maxim WIRING DIAGRAM

1981-83 XJ550 Seca WIRING DIAGRAM

The World’s Greatest XJ550 Seca Wiring Diagram:

1980-82 XJ650 Maxim, Midnight Maxim, and Seca WIRING DIAGRAM




1982-83 XJ750 Seca WIRING DIAGRAM



Components Key Guide for all of the above WIRING DIAGRAM




Brand new OEM and replacement batteries will certainly solve those slow or no-start problems, but before you buy a battery............read on to determine whether you really need a battery, or whether your situation is due to some other cause.

Of course, if you determine that your battery is ready to take that trip to the great lead-acid Heaven in the sky......or, actually, to a recycling center, such as a local auto parts store........then we have a variety of choices for your specific bike.

How do I know if my battery is good?:

Is it your battery, or your charging system, or something in-between?

The best way to know for sure is to use a multimeter (voltmeter) attached directly to your battery positive and negative terminals, and observe the following:

1) with the engine and all electrical accessories off, the battery should read a minimum of 12.8 volts DC. If not, the battery is either not fully charged, or it is bad (it is incapable of holding a full charge). Charge the battery fully and check again; if the reading is less than 12.8 volts, the battery is bad and should be replaced.

NOTE: most manuals describe checking the specific gravity of each battery cell electrolyte (fluid) as the preferred method of checking the condition of the battery. This reading should be between 1.2650 - 1.280 per cell. If a fully charged battery cannot reach these levels in all cells, then that cell is bad and the battery should be replaced.

2) If the first test above passes, leave the multimeter hooked up to the battery terminals, and press the starter button. While the starter is engaged (but before the bike starts), the battery voltage should be 9.5 volts or greater. If not, then this signals either a bad battery, very dirty or weak electrical connections, or it could be a incredibly problematic starter motor (not likely; it's probably the battery!).

3) if you run into this specific problem:

* "There were a few times when I cranked it, that it ALMOST started. It would start to fire immediately as I let off the start button. But it just wouldn't catch.

Then this is a symptom of a weak battery, due to any number of causes.......

What happens is that as the starter is being engaged, it gobbles up battery voltage. As soon as the start button is released, you now have full battery voltage available TO THE IGNITION CIRCUIT (including the pick-ups, the TCI, and especially the coils), and in that instant when you release the starter button, the coils get enough voltage to produce an adequate spark while the motor is still (by inertia) turning over. If everything is in a great state of tune, the bike will normally kick over. If not, you get the "almost fires" situation explained above, so.........

Test the battery voltage WHILE THE STARTER IS ENGAGED (a voltmeter across the + and - terminals of the battery is all that's needed). It should remain above 9.5 volts while the starter motor is engaged but without the engine running. If it drops below that level while the starter is active, then that's the "problem", and the cause of that problem must be determined and remedied (usually a sign of a bad battery, or it could be a incredibly problematic starter motor).

4) Your charging system output VOLTAGE should be checked, again at the battery terminals, while the engine is running. The measured voltage should be:

* 14.2 - 14.8 Volts at about 2,000 rpms for all non-X models, and the same voltage for "X" models, but at about 3,000 rpms. Again, you would measure these voltages at the battery terminals with your voltmeter.

NOTE: If your alternator is outputting more than 14.8 volts to the battery, your regulator-rectifier unit is bad and should be replaced. Over-charging a battery will quickly ruin it, and may cause severe damage or failure of other electrical components, such as the TCI or the computer monitor system (on bikes so equipped).

Here's your cheat sheet on all of the above:

Static Battery Voltage Test

Prior to conducting this test, make sure the battery has not been
recently charged. You must wait at least one hour after charging
your battery to conduct this test.

a) Adjust voltmeter to DC volts (20 volt range).

b) Place voltmeter leads to the battery terminals (positive to positive and negative to negative).

c) Read voltage and refer to the chart below.

State of Charge:

100% Charged with Sulfate Stop:
Using a syringe Hydrometer: 1.280
Using a Digital Voltmeter: 12.80 volts
Using a Floating-Ball Hydrometer: 5 balls floating

100% Charged:
Using a syringe Hydrometer: 1.265
Using a Digital Voltmeter: 12.60 volts
Using a Floating-Ball Hydrometer: 4 balls floating

75% Charged:
Using a syringe Hydrometer: 1.210
Using a Digital Voltmeter: 12.40 volts
Using a Floating-Ball Hydrometer: 3 balls floating

50% Charged:
Using a syringe Hydrometer: 1.160
Using a Digital Voltmeter: 12.10 volts
Using a Floating-Ball Hydrometer: 2 balls floating

25% Charged:
Using a syringe Hydrometer: 1.120
Using a Digital Voltmeter: 11.90 volts
Using a Floating-Ball Hydrometer: 1 ball floating

0% Charged:
Using a syringe Hydrometer: less than 1.100
Using a Digital Voltmeter: less than 11.80 volts
Using a Floating-Ball Hydrometer: 0 balls floating

Starting Load Test:

a) Adjust voltmeter to DC volts (20 volt range).

b) Place voltmeter leads to the battery terminals (positive to positive and negative to negative) .

c) Watch the voltmeter as you start your motorcycle, but before the engine is running.

d) If the voltage drops below 9.5 volts, the battery has very low capacity and should be replaced.

Basic System Operation Test:

To test and see if the alternator is actually getting power to it (along the brown and green wires) you verify whether a magnetic field is being created inside the rotor and stator. Be sure to use a thin feeler gauge when performing this test, since the magnetic field being created is not all that strong outside the generator cover….but it will exist if the system is performing.


Hold the extended feeler gauge blade and 1/4” away from the AC generator cover and when the key is turned on the feeler gauge should pull towards the cover. The rotor should be receiving maximum excitation when the engine is not running. You should be able to measure about 12-volts on the brown wire, and approximately 1.8-volts on the green wire. The voltage regulator controls the low side (green wire) and will raise and lower the voltage based on internal voltage sensing within the regulator.

Charging System Tests:

a) Adjust voltmeter to DC volts (20 volt range).

b) Place voltmeter leads to the battery terminals (positive to positive and negative to negative).

c) Start the engine.

d) Bring engine up to approximately 2,500 rpm's.

e) Compare the voltage reading to the specification given below:

For all XJ-series models, the maximum available charging output VOLTAGE should be as follows (all values are approximate):

* approximately 500-2000 rpms: 12.6 volts gradually increasing to 14.2 volts
* 2000+ rpms: 14.2 volts up to about 14.8 volts, with a maximum of 14.8 volts (all models except XJ700-X and XJ750-X)
* 3000+ rpms: 14.2 volts up to about 14.8 volts, with a maximum of 14.8 volts (all XJ700-X and XJ750-X)

NOTE: the voltage reading must be approximately 14.0 - 14.5 volts to properly charge an AGM battery......anything less, and you will quickly kill these type batteries!

If your charging voltages are too low, suspect the alternator brushes first, then perform the alternator stator and rotor checks as described in the Alternator Section elsewhere in the catalog. Alternator brushes should be replaced whenever they are less than 11mm in overall length......the factory maintenance interval indicates that you should expect to replace these brushes every 8-10,000 miles. Factory brushes have "wear marks" (scribed lines) on the brush to indicate their wear limit; these aftermarket brushes also have the scribed wear line. Overall length of these brushes are 17.10mm, with 9mm of length from the wear bars to the contact end of the brushes:


If your charging voltages are too high, suspect your Regulator - Rectifier unit first, and perhaps dirty or corroded electrical terminals. The procedure for checking these is too detailed to describe here, and you should consult your service manual for additional details.

5) Check the condition of your main circuit terminals.....they should be zestfully clean and un-corroded, or you're primed for a variety of problems......not only will your circuits not be getting full power out of your battery, but to add insult to injury, your charging system may think that the battery needs more juice, and so it starts cranking out amps like there's no tomorrow. It's pretty safe to say that neither of those two occurrences qualify as a Good Thing (tm), so...........start at the beginning, and inspect and clean (and then protect, like with di-electric grease or equivalent) all the [/b] terminal connection points[/b]:

* the positive battery post connection to the positive battery cable.
* the positive battery cable connection to the starter relay (or "solenoid").
* the main harness terminal connector from the starter relay.
* the main lead from the starter relay to the starter motor (both ends).
* the "main fuse" contacts inside the fusebox.
* the battery ground cable contacts at both the engine case and at the negative battery post (poor ground are just as bad as poor positive feeds; after all, it takes two to tango, or to complete a circuit, and electricity doesn't care where the restriction occurs).

Battery and Charging System Results:

Okay, now with all of the above out of the way, you should be able to determine whether you need a new battery, or not. There's no need to waste money on a replacement battery if it's not the root cause of your problems. If your battery is good, but your charging system or electrical system isn't, then spend your time and money on fixing the root causes of the problem........such efforts will also help prevent you from murdering your otherwise good battery.

But assuming that your battery is ready to be retired, the question then becomes, which battery?----as they come in a variety of types and price ranges (and, as with most things in life, the more you spend, typically, the better quality you'll get when it comes to a "commodity" product such as a battery).

Basically, motorcycle batteries are of two basic types, the flooded cell type (sometimes called a "wet cell" or "conventional" battery) and the AGM or "absorbed glass mat" type.

Your original-style, Yuasa-brand battery was a "conventional" type, and these are now available in both their original configuration, or in a high-performance version that can output more amperage than the standard style-----and this is typically a cost-effective upgrade.

AGM batteries feature cell separators made of fiberglass mats that minimize the movement of electrolyte (acid), and prevent spillage if tipped over on their side. The acid formulation in these also typically a bit stronger compared to flooded cell batteries, which accounts for their typically higher output. AGM batteries are of the permanently sealed, "maintenance-free" design, thus never requiring the further addition of water or acid.

The charging system of many modern motorcycles that come factory-equipped with an AGM type battery uses a regulator/rectifier that outputs a slightly higher voltage than a flooded cell battery requires. Using an AGM in almost any motorcycle will usually work well, while using a flooded cell battery in a bike designed for an AGM type will often result in overcharging and quick boiling of the electrolyte solution -- it isn't long before the battery is dry and possibly ruined. Of course, all of our XJ-series bikes came originally with a conventional wet ("flooded") type battery, so replacing them with the AGM types is not a problem or issue.

AGM type batteries are also more tolerant of sitting for long periods with minimum formation of lead sulfate (sulfation) on the plates. They can usually be charged at a slightly higher rate and in general provide better performance over the long haul. However, once AGM batteries are "dead"; they're dead, and cannot usually be brought back to life (even for a short amount of time) like a conventional battery can.

Finally, be aware that while AGM batteries are sometimes incorrectly called "gel cells batteries", a true "gel cell" type of battery is quite a different animal, and is actually not recommended for motorcycle use.

Battery FAQ's:

What is a conventional (or "wet" or "flooded") battery?:

These are the standard automotive type design battery, with individual push-in or screw-in battery cell access caps, a vented design, also referred to as a "lead-acid" design, and need the periodic addition of distilled water to "top up" the fluid level.

What is a "maintenance-free" battery?:

Maintenance-free batteries do not require the addition of water after their initial fill of their water/acid electrolytic solution. It means that it is a "sealed" battery, with no filler caps. Note that while conventional "wet" batteries may be available in a sealed, maintenance-free variety, AGM batteries are always of this sealed, maintenance-fee type.

What is a "high-performance" battery?:

Due to plate design and other factors, high-performance batteries have a denser charge ability and will output more amps for a longer period of time (this is the so-called Cold Cranking Amps or CCA rating number that is used to describe a battery) before full discharge. Although there have been some interesting technological "enhancements" to the basic conventional battery design over the years, almost all "high-performance" (meaning, higher-capacity) batteries rely on more lead material in their plates, resulting in a physically heavier battery. More lead = more money to manufacture and transport the battery, which is why these batteries cost more.

What is an AGM battery?:

AGM is an abbreviation for "absorbed glass mat". In this battery design, almost all of the battery sulphuric acid solution --- which, by the way, is typically at a higher concentration level than of what is used in conventional "wet-cell" batteries --- is absorbed into glass mat separators which are sandwiched between the lead plates. It's a totally sealed and maintenance free design. There are no discharge tubes or fillers caps, which eliminates the need to maintain water levels and offers no concern about acid leaks on valuable parts and accessories.

AGM batteries offer the following advantages over conventional batteries because:

a) their sealed, maintenance-free design means you never have to worry about checking nor maintaining their fluid levels.

b) AGM batteries, unless physically damaged, will not leak or corrode your paint and chrome.

c) they have less internal resistance which offers more cranking amperage than wet batteries.

d) their lower self-discharge rate means they can sit for extended periods of time without constant monitoring. A conventional wet battery discharges 15% a month, whereas AGM batteries discharge only 2-3% a month.

e) a longer service life be expected from an AGM battery-----the main reason conventional wet batteries fail is due to water levels that are not properly monitored and maintained. Conventional batteries are also not very heat nor vibration resistant. AGM batteries are much more heat and vibration resistant than conventional batteries, and of course are maintenance-free, all of which contribute to their longer service life.

f) however, AGM batteries are more sensitive to both undercharge and overcharge conditions than conventional wet-cell, lead-acid batteries. They must be maintained correctly, and use a quality "smart" charger that does not stray too much, or too long, into the "overcharge" range of charging.

What is a gel-cell battery?:

A type of battery that you do not want to use in your XJ-series bike!

What are the electrical specifications for an original battery?:

all XJ550 and XJ650 models:

Capacity: 12ah
Charging rate: 10 hours @ 1.2A
CCA's: 113

all XJ700, XJ750, and XJ900RK models:

Capacity: 14ah
Charging rate: 10 hours @ 1.4A
CCA's: approximately 130

XJ1100 models:
Capacity: 20ah
Charging rate: 10 hours @ 2.0A
CCA's: 260

How should a battery be maintained?:

Good battery maintenance allows you to get the maximum power and life from your battery:

a) always keep the acid level between lower and upper lines on front side of the container (for conventional type batteries that are not sealed).

b) do not let the battery remain in a discharged condition for any length of time. Discover and remedy the cause of such a condition immediately.

c) when a bike is stored for over 30 days at a time, use an automatic battery charger to maintain a proper storage charge.

d) keep the top of the battery case clean, dry, and free of dirt or moisture.

e) clean the battery terminals to prevent corrosion, and treat them to some anti-corrosion spray or coat their exposed areas with di-electric grease. Do not over-tighten the terminal cinch bolts!

f) inspect the battery vent tube regularly, ensuring that it is not bent, twisted or clogged, especially at the bottom of the tube, where it discharges towards the ground......this is the most common place where the tube will get clogged via road debris, etc.

g) protect the battery from strong impacts or shocks.

How long will my new battery live?:

Regardless of battery type or manufacture, you can expect a properly activated, and properly maintained battery (meaning it's neither overcharged nor overly or repeatedly allowed to become fully discharged) to give you 2-4 solid years of life.

Heat is the big enemy of motorcycle batteries----they'll last much longer in a cool climate than a hot one. The self-discharge rate of a battery can run as high as 3% a day in hot weather with a flooded cell battery to about 1% or less per day with an AGM type. Overcharging a battery also overheats a battery---a double whammy! Make sure your charging system is in good order to get the maximum life from your battery.

Constant, repeated complete discharges of a battery will also reduce their lifespan. There's only so many times you can "drain the well" before a battery electrically gives up the ghost.

What are some of the best ways to kill a battery?:

a) Let a discharged battery freeze. Fully discharged batteries freeze at about +25-F, or just below the freezing temperature of water. Fully charged batteries freeze at about 75-F below zero. 'Nuff said........

b) Let a battery overheat.

c) Overcharge the battery........either via the use of an incorrect (or poor quality or defective battery charger), a charging system regulator gone bad, or highly corroded (high resistance) wiring harness connections within the system.

d) "Quick-charge" the battery using an incorrect style battery charger.

e) Allow the fluid level (for wet or conventional batteries) to get too low. This exposes the plates to air, which cause the plates to "sulfate", which leads to increased electrical resistance and a drop in power output.

f) Run a battery down into deep-discharge. Each full discharge event causes sulfate build-up on the lead plates. Do this enough times.....like when your charging system isn't outputting properly........and you'll kill a battery pretty quickly.

g) On conventional batteries, do not use regular tap water to fill or re-fill the battery. Tap water contains minerals and metals that will shorten the life of a battery. Always use distilled or de-mineralized water to fill a battery.

What about my original battery fluid level sensor?:

Some original models with the "computer" dashboard monitor system (1982 XJ750 Maxim, 1981-83 XJ750 Seca, and XJ1100 models) had a low-battery-fluid warning light on the dash, triggered by a fluid-level sensor which replaced one of the battery cell screw-in caps. If the fluid level in that battery cell was too low to trigger the sensor, the circuit in the computer dash warning system would read that as a low-voltage condition and would then illuminate the warning light.

So of course, the first issue in regards to these sensors is: if the light is on, first check your fluid level!

But other issues arise: it could be that the tip of the sensor has become dirty, or encrusted with deposits, in which case even if the fluid level is fine, it will still sense a low-voltage condition. This can be remedied with a gentle cleaning of the sensor tip (steel wool, brass bristle brush, etc.).

Also, the sensor reads voltage, and without enough voltage to trigger the computer system, the light illuminates. The wire path from the sensor goes through your ignition switch and if this switch has electrically "dirty" internal contacts, then that can add enough resistance to cut the voltage signal enough to trigger the dash "low Batt" warning light or display, even though the sensor is fine and the fluid level is okay! So: remove the ignition switch, and its bottom plate, and clean the copper contacts inside the ignition switch.

Finally: a few issues arise with replacement batteries in regards to the use of sensors:

a) some batteries are designed to allow you to re-use your original sensor (we also offer a replacement sensor in case your original is missing or damaged). These conventional-style batteries will feature screw-in caps and your original sensor will screw right in place (by the way, the sensor must be installed in the 4th cell over from the negative post or it will not work correctly and may damage your dash computer!).

b) but some aftermarket batteries, even though they have screw-in caps, have a different "plate depth" internally, and even though the original sensor will screw into the cell port, the sensor tip will be too deep and contact the lead plates in the battery which will cause battery, sensor, and dash computer damage! Thus you must be careful with aftermarket batteries, and measure the depth of the cell, and if it's shorter than that of an original battery, you must use plastic spacer shims (washers) to space an original sensor "upwards" to the proper depth for such batteries, or carefully trim the sensor tip shorter so that it does not ever contact the internal plates.

c) other aftermarket batteries will have push-in rather than screw-in caps. An original sensor will not fit into these batteries unless that one cell port is "threaded" to accept the sensor. This can be best accomplished by gently screwing into the cell port a proper sized and thread steel bolt, and thus "cutting threads" of the proper size into that cell port opening. Now your original screw-in sensor can be properly installed; however, the same warnings as in issue "b" above (in regards to the depth of the cell) must be observed and remedied, if necessary. Of course, make sure that as you cut these new threads into the battery case, that any plastic "shavings" that are created by this threading process do not get into (or are removed) the battery cell.

d) some of the replacement Yuasa batteries that we offer come with a replacement sensor.......in which case, you discard (or save) your original sensor and just hook up your sensor wire lead to this new sensor.

e) some aftermarket batteries.....such as the replacement "maintenance-free" (sealed) and all AGM batteries......have no "cell caps" and thus are not going to accept a sensor, at all. This present a problem, since the lack of voltage to the dash computer makes it think that there is a battery problem, and the red warning light or display message is always on or blinking at you. Although you can "reset" this annoyance away, there are two other solutions available to you in order to disable or bypass this function:

i) on models that use a warning light, you can simply remove the bulb from your dash! No more "warning" of a low battery fluid condition (except on the LCD display screen), but no more annoying blinking light, either.

ii) on all models, you can install our HCP9982 sensor bypass wire that duplicates the function of the original sensor.

What are the best battery myths?:

a) that putting a battery on a cement floor will cause it to discharge. This may have been true a long time ago, when the battery case was made of a rubber material, which would develop hairline cracks and thus allow moisture to permeate into the case, opening up an electrical circuit which would quickly discharge a battery. Modern batteries use molded plastic cases that do not suffer from such a fate.

b) that bringing a battery inside during the winter will prolong its life. Batteries produce electricity via a chemical reaction, and the chemical reaction results in the production of sulfate deposits on the lead plates within the battery, and these sulfate deposits act as electrical insulators----thus reducing the power output and the overall life of the battery. These chemical reactions slow down dramatically with lower temperatures. As long as your battery does not freeze, the lower the temperature, the less the amount of chemical reactions taking place, thus prolonging the life of the battery!

Remember, heat is one of the things that wears out batteries, because they speed up the amount and intensity of these chemical reactions that creates the sulfate deposition on the lead plates.....and those deposits are what really "kills" the battery.

By the way, the main reason why your car or bike cranks over so slowly during winter is not due to "thicker oil" (multi-viscosity oils took care of that issue a long time ago), but because of the decreased chemical reactions (meaning less electrical output generation) within the battery due to those lower temperatures.

Can I jump-start my dead motorcycle battery from a car battery?:

Yes, BUT.................

a) you need to make sure that you are using the proper gauge jumper cables.

b) hook the jumper cables up incorrectly (+ to -) and if you're lucky, you'll just burn up your TCI unit. If you're unlucky, you'll blow up your battery, your bike, or yourself.

c) make sure that your key switch and all electrical power drains are OFF before you hook up the jumper cables.

d) the best sequence of battery connection is to hook up both jumper cables onto the dead battery first, and then connect the positive lead to the good battery, and finally the negative lead to the good battery (or a good ground on the donor battery frame, etc.).

Your quest for more battery knowledge may still remains unsatisfied; if so, a great battery tutorial can be found at:





Battery sensor bypass install:

http://www.xj4ever.com/HCP14180 battery sensor bypass.pdf


This should be on the very top of your "to-do" list, it will save you untold hours of grief and frustration down the road (no pun intended!):

Replacement Fuseboxes:

Upgrading your electrical system couldn't be simpler with one of our aftermarket style enclosed, waterproof fuse panels.....bringing your bike a long way up to 21st century standards of electrical wiring, and helping to prevent and eliminate annoying, frustrating, and down-right dangerous electrical issues that worn out stock fuseboxes suffer from.

So, if your fusebox (or the remains of it) look anything like this:


or this:


then it's time to solve a number of problems and potential problems, all at once!

And here is the shocking video that everyone’s talking about, showing the entire install on an XJ650 Maxim model (other models, besides the XJ100 and XS1100 models, are all basically the same procedure):

FITMENT: the stock Yamaha fusebox is very flat...less than an inch tall. These aftermarket fuseblocks are quite a bit taller, and therefore may present some challenges and the need for some creative engineering to place them properly. In some cases the small "document holder" under the seat may need to be removed. We offer the following tips:

XJ550 models (all): the stock fusebox lays on top of the "tool kit caddy", and the forward "arms" of this caddy hold both the TCI (on the right side) and the fusebox (on the left side). These aftermarket fuseboxes will not fit in the same place as the stock fusebox, as the increased height will cause interference with the bottom of the seat pan. The best fit can be obtained by carefully cutting away a portion of the left tool caddy "arm", so that the replacement fusebox can be attached to the top of the air filter housing. Careful positioning of the fusebox will allow you to remove a minimal amount of the tool caddy arm material, thus retaining the structural strength of that arm. The replacement fusebox should them be retaining to the top of the air filter box via two self-tapping screws, or proper sized bolts and nuts. Here is a good image of what it should look like when you're done:


XJ650 all models (except Turbo) and all 1981-83 XJ750 models: the stock fusebox lays on top of the air cleaner box lid. The replacement fuseblock can go in the same area, but some care must be taken as to positioning to make sure that the bottom of the seat pan does not contact the top of clear cover of the fuseblock. You will have to slightly reposition the fuseblock from the original mounting holes to get everything to line up properly, and you may have to remove the small plastic "document holder" that snaps into the bottom of the seat pan to secure proper clearance. Most clearance issues on these models can be resolved with the use of our FITMENT TEMPLATE and SEAT SPACER KIT listed further below.

Here are the basic steps needed, shown on an XJ650 Maxim model; XJ650RJ Seca and XJ750 Maxim and Seca models are similar. Although this how-to uses a 4-circuit replace fusebox, our 6-circuit panel installs in the same manner:


XJ650 Turbo models: the stock fusebox fits into a flat plastic holder "bar" that fits over the air cleaner box. This holder will no longer be used, and the replacement fusebox will need to be screwed directly to the top of the air cleaner box.

XJ700 and XJ750-X models: these bikes already use the push-in type fuses in a fuse panel (under the gauges) that already comes with ATC style fuses for the auxiliary circuits, and there is no need to upgrade that! Therefore these replacement 6-circuit fuseboxes are not needed on these bikes. However, they also use a 30A main fuse in a separate in-line fuse holder that uses the old glass-style fuse, and that is certainly a candidate for updating with the 30A ATC style in-line fuse holder HCP6833 listed further below.

XJ900 (and possibly XJ750RL) models: the stock fusebox sits in the "electrical components compartment" caddy under the seat. The replacement fusebox will fit in place of the original fusebox inside this caddy, but you will need to add the HCP12836 spacers to the frame tubes to space the seat pan up slightly (1/8") to prevent interference between the bottom of the seat pan and the top of the fusebox. Here's a great visual how-to:


XJ1100 models: some slight modification to the battery tray will need to be done; here is a good illustration of the installment procedure on these models:


Also available are harness WIRING EXTENSION KITS that contain all the additional color-coded wiring leads, terminals, and connectors needed to make the installation of these aftermarket fuseboxes an even simpler fix!


This information should assist you in visualizing what the starter motor rebuild process will involve. Although shown is the XJ650/700/750/900 type starter motor, the same process applies to all XJ models:




and a great video of the entire process from start (no pun intended) to finish:





Yikes, this seems like a lot of work!



http://www.xj4ever.com/clean and lube the ignition switch.pdf








The following guide to understanding your charging system was contributed by Dwayne Verhey, extreme XJ-Wizard.

There are two main types of alternator systems commonly used on motorcycles. Both types depend on a magnetic field, created by magnets in the alternator rotor, to induce an electrical voltage and current flow in a stationary coil of wires-----the alternator stator. If you ever get confused as to which is which, just remember that the rotating component is the "rotating rotor", and the spaghetti-like bundle of wires is the fixed-in-place, "stationary stator"......

The first type is the permanent-magnet rotor system (used on Virago, V-max, and FJR models, among others). In these systems, the fixed-strength magnets in the spinning rotor generate a constant-strength magnetic field, and thus excite the stator coil constantly; thus the alternator puts out 100% current at all times and the voltage regulator merely serves to shunt any excess generated current to ground. The advantage of the permanent-magnet system is a reduced amount of system complexity, but at the cost of increased heat and power losses (since the alternator system is generating power, and thus using up engine horsepower, constantly).

The XJ-series of bikes follows the more common automotive model, which employs variable-strength electro-magnets in the rotor. In these systems, the variable-strength magnets in the spinning rotor, when energized, are used to form the magnetic field which excite the stator. The voltage regulator controls the voltage output by varying the input voltage applied to the rotor's electro-magnets, and thus varies the strength of the magnetic field. If the system voltage drops, the voltage regulator increases the voltage fed into the rotor electro-magnets, thus increasing the strength of the magnetic field that the magnets produce, and therefore increasing the excitation (output) from the stator....and thus the alternator output voltage increases.

In both systems, the stator windings are 3-phase. Each stator wiring bundle (there are 3 of them, and each bundle is called a "leg") kicks out similar voltage, but 120-degrees out of phase with the adjacent leg(s). The resulting AC currents are then rectified (changed) to DC current via a 3-phase bridge rectifier, made up of 6 diodes, such that current in any leg flowing in either direction is directed back into the system as 12-volts DC (actually, around 13.5 to 14.5 volts DC, when everything is working properly).

If you lose a leg, or even a single diode, it is possible to still achieve voltage if the load is minimal, but as current requirements increase, the alternator will not be able to meet the challenge and the battery will have to take up the slack. Of course, as the battery drains, the available voltage is reduced, so the maximum rotor field voltage is reduced, so the current output is reduced, so the battery has to take up more slack, so ....

The end result is the battery discharges and the bike won't start.

If you suspect alternator issues, do the following checks, in this order:

- first check the resistance on the wires to the rotor. If resistances are out of spec, then check for dirty rotor commutator rings, corroded connections, etc.----all of these problems will reduce the available rotor field voltage.

- next, check the condition of the connectors from the stator to the rectifier (the 3 white wires). There's usually 2 connectors -- one from the alternator, often hidden behind the battery box, and the other near the regulator. Corrosion in these spots will reduce the stator's outputted current (bad corrosion will often melt the connector, as the outputted current turns into heat rather than being delivered to the battery).

- finally, using your multi-meter and following the directions in the service manual, check the function of each of the 6 diodes in the rectifier to make sure the power is being properly rectified from AC to DC.

Alternator Stator:

Checking alternator stators:

These tests should be taken while the components are at a temperature of about 70-F:

a) with the engine off and key off, measure the resistance across each pair of the three white wires (white1, white2, and white3) --- thus you take a separate measurement for white1 to white2, white1 to white3, and white2 to white3 ---- at the connector should be as follows. This test is measuring whether there is any internal short within each wire bundle.

0.50 ohms +/- 10% for all XJ550 models.

0.46 ohms +/- 10% for all XJ650, all XJ700, all XJ750, and XJ900RK models.

0.37 ohms +/- 10% for all XJ1100 models.

0.40 ohms +/- 10% for all XS1100 models.

b) with the engine off and key off, measure the continuity between each wire to ground (battery negative post or engine case, etc.). Thus white1 to ground, white2 to ground, and white3 to ground. This test is measuring whether there is any short within each wire bundle to the external world.

c) with the engine running, back-probe each of those 3 white wires at their connector to ensure voltage is being generated on each leg. NOTE: the voltage on those 3 white wires is AC, not DC, so be sure to set your voltmeter properly. AND, YOUR CHECK WILL BE BETWEEN WIRE PAIRS (white1 to white2, white2 to white3, and white1 to white3….and it doesn’t matter which one you consider wire #1 or #2 or #3 to be, as long as each wire’s output is checked)……AND NOT TO THE FRAME OR (GOD HELP YOU) TO THE BATTERY NEGATIVE. You should see some voltage (the actual amount is meaningful, nor specified) on each test, and the voltages should be about the same on each leg.

Alternator Rotors and Field Coils:

Checking alternator rotors or field coil: the resistance across the two lead wires (usually brown and green) at the connector should be as follows. Note that worn or damaged alternator brushes can affect these readings, as can "dirty" copper commutator rings on the rotor face (where the brushes contact the rotor):

4.5 ohms +/- 10% for all XJ550 models.

4.0 ohms +/- 10% for all XJ650, all XJ700, all XJ750, XJ900RK, and XJ1100 models.

3.5 ohms +/- 10% for all XS1100 models (field coil).

NOTE: for best performance, your alternator Stator and Rotor (or, the Field Coil on XS1100 models) should be replaced at the same time.



Before we get into the list of components within your ignition system, it may be useful to explore the basics of the ignition design used on these bikes, as this knowledge may help you to better recognize, troubleshoot, and repair performance problems with your engine that you think may be due to these components.

The ignition system actually begins at the left end of your CRANKSHAFT, since the rotational position of the crankshaft determines the position of the pistons and of the camshafts. Obviously, since the purpose of the entire ignition system is to deliver a high-voltage spark at the plugs at exactly the proper instant----meaning, as the piston approaches Top Dead Center of the compression stroke----then the ignition system must "know" what the position of the crankshaft is in order to transfer that information (via electrical signals) to the major components: the PICK-UP COILS, then onto the TCI UNIT, to the IGNITION COILS, via the PLUG WIRES and through the PLUG CAPS and finally, onto the SPARK PLUGS.

But it all begins at the crankshaft, which has a flat metal ROTOR DISC bolted onto the left side snout, and which hides under the left side, round "Oil Pump Cover" (also called a "YICS" cover on YICS-equipped engines). This spinning rotor disc has a small magnet embedded within it's outer tip, and as that outer tip rotates past the fixed magnets within the PICK-UP COILS, the interaction of magnetic fields triggers a small voltage in the pick-up coil wires that lead to the TCI UNIT.

Note that since the rotor disc is fixed in position and spins along with the crankshaft, this rotor disc "knows" the position of the crankshaft at all times. And since the pick-up coils are bolted in place, and are thus stationary, whenever the spinning rotor passes by a fixed pick-up coil, and thus triggers it to send a voltage signal to the TCI, in this way the TCI unit thus also "knows" where the crankshaft is, rotationally-speaking, and thus where the pistons are in relation to Top Dead Center and when their spark plugs need to be fired.......

Also note that since there are only two pick-up coils for your four-cylinder engine, that each pick-up coil is actually providing the "firing signal" to the TCI unit for two different cylinders. In these engines, one pick-up coil is responsible for sending the signal to the TCI that eventually leads to the spark plugs firing off for cylinders #1 and #4 at the same time, and the other pick-up coil sends the message to the TCI unit to fire off spark plugs #2 and #3, again, at the same time.

Although this may seem odd at first, the mechanical arrangement within the engine of the crank throws, and thus the rods and pistons, as well as the camshaft timing, allow this situation to proceed without a problem; in fact, when one of these "paired" cylinders (for example, #1) is approaching Top Dead Center of it compression stroke----and thus is in need of a spark from its spark plug----it's "mated" cylinder (#4) is also approaching Top Dead Center, too.........but on its exhaust stroke.......and so even though cylinder #4 gets a spark at its spark plug, there's nothing in the cylinder to combust, and thus it's a "wasted" (yet harmless) spark that occurs in cylinder #4.

Obviously, the exact same situation occurs in the mated pair of cylinders #2 and #3.

In fact, the whole system is known as the "wasted spark" system, since one of the two sparks that always occur at the same time is "wasted" on a cylinder that is on its exhaust stroke............

Anyway, to continue our journey: when a pick-up coil is energized by the passing magnetic field of the spinning rotor disc, it send an electrical impulse signal to the TCI. Therefore, the TCI unit now also "knows" the position of the crankshaft (and thus of the piston). Using other sensor information.....primarily, the rotational speed (RPM's) of the engine......the computer chip in the TCI is then responsible for calculating exactly when to send a "message" to the proper IGNITION COIL to release it's energy to the proper cylinders. And note that we said "cylinders" (plural), since just like the pick-up coils, one ignition coil also sparks two cylinders at once (part of the same "wasted spark" method discussed above).

The ignition coils use a rather small (12V) input on their primary side to product a large (20,000V +) amount of electrical energy on their discharge (spark plug wires). When the TCI unit determines that "the time is right" for a particular coil to fire, it grounds that coil, which collapses the small magnetic field inside the primary side of the coil, which thus induces a large electrical field in the secondary (plug wires) side of the coil, which then rushes to ground. This electrical energy rushes down the non-resistive PLUG WIRES, through a resistor in the SPARK PLUG CAP, and finally jumps a small gap in the spark plug electrode on it's way to ground, and thus the spark occurs that fires the air-fuel mixture (in one of the two cylinders being sparked at the same time), things go boom, power gets produced, and you're on the way down the road........

A great explanation and diagram---starting at the 4:15 mark in the video---explains all of the above in a very simplified, yet understandable detail:


By the way, the firing order for the XJ550 thru XJ900 engines is 1-2-4-3, with the two center pistons coming up while the two outer pistons are going down, and the direction of engine rotation is in the same direction as your tires rotate when moving forward.

Now, What Could Go Wrong?:

Well, remember, all of these components are basically used to transmit knowledge of where the piston is within it's four-stroke cycle, and to be able to deliver a spark at the appropriate time to each cylinder to take advantage of the compressed air-fuel mixture in the cylinder (during the compression stroke). So it sometimes help to understand these component pieces as being mainly responsible for providing this stream of precise information, and the electrical-spark making (at the spark plug gap) as merely being the natural (according to the laws of physics and electricity) end-result of all this information handling and processing.

Now, unless your crankshaft was installed backwards (an impossibility, by the way!) or the camshaft was installed improperly (or if the camshaft drive chain has skipped a tooth----not a common occurrence, at all), then we can safely ignore all of these issues. And since the spinning rotor disc used to trigger the pick-up coils is bolted firmly in place at the end of the crankshaft, it can be ignored for troubleshooting issues.

But the pick-up coils themselves can go bad over time, and even though it's rare, it can happen. No pick-up coil signal out----along their wires to the TCI unit-----means no signal into the TCI unit, and the whole system breaks down. Which means the small wires from the pick-up coils to the TCI had better not be pinched, shorted to ground, or broken internally, or the message just won't get through.

NOTE: if you are having intermittent or difficult-to-diagnose ignition system problems, it may be that the wire leads from the pick-up coils (under the left round crank-end cover) have become pinched where they exit the cover and have worn through their insulation.

Of course, if the TCI unit itself is defective, then even if it is getting a signal from the pick-up coils, it is unable or unwilling to process the signal, or the signal gets processed incorrectly, and either the signal doesn't get sent to the ignition coils at the proper time, or doesn't get sent at all.

But even if the pick-up coils and the TCI are performing flawlessly---which they usually are----if the ignition coils are not getting enough voltage input to them, or, if they are not able to multiply the small incoming voltage into a much higher output voltage (that is, after all, their main purpose in life), then we have a problem.

Worn-out ignition coils, or coils that perform poorly or get cracks in their outer cases (and thus short out when moisture enters their internal shells), are a common cause of ignition system problems.

And even if the coils are performing properly, if the spark plug wires have an internal break, or an external break, and thus prevent the coil electrical output from reaching the plugs, then nothing good is going to come from all this activity.

Of course, the spark plug Resistor Caps also play a role. They have a tiny resistor embedded within them, and the purpose of the resistor is to provide, of course, electrical resistance to the flow of electrical energy. There are a couple of reasons why some resistance is necessary-----it helps eliminate electrically-generated Radio Frequency Interference "noise" (RFI), it provides a "cushion" against instantaneous electrical energy pulses (which is really hard on small, fragile electrical components, such as the capacitors and transistors in the TCI unit), and it "slows down" the passage of the electricity through the spark plug, thus providing a sort of "electrical Viagra" to spark at the plugs, allowing the electrical discharge (and thus the spark) to last a bit longer (instead of being instantaneous), thus promoting more-better and fuller combustion of the air-fuel mixture.

In fact, outside of the RFI suppression issues, it is the control of this "spark burn time" that is really the most critical issue, especially on bikes that are jetted a bit lean to begin with........as increased electrical resistance in the secondary circuit will increase the spark firing or "burn" time, and that longer burning spark assists in the more complete combustion of harder-to-fire lean fuel mixtures.

But those resistors in the spark plug caps........or in the spark plugs themselves, for those engines that use resistor plugs........do wear out over time. And when they do, their resistance increases, which means that they provide more resistance to the flow of electricity than is needed. So that 20,000 volts of electrical energy, instead of being discharged at the spark plug gap in a rather short (10 milliseconds) amount of time, gets "spread out" over a much longer period of time, and gets reduced in voltage, too. So when plug caps or plugs "go bad", they rarely fail to the point where no spark occurs at all, it's just that the electrical output is being "spread out" over such a long period of time that the energy being created in the spark plug gap is so low that it's not enough to fire the fuel mixture completely (or at all)........and that's what leads to hard starts and poor performance (and reduced gas mileage, too).

By the way, as you may have figured out by now, a spark plug that is contaminated ("fouled") by carbon or oil deposits, or one which has too large of a gap, fail to operate properly mainly because such situation can greatly increase the electrical resistance characteristics of such a plug.........and now you know why that's not a good thing.

NOTE: some models specify a different (higher) plug cap resistance for the inner 2 cylinders vs. the outer cylinders. The probable reason for this is that the inner pair of cylinders may run a bit leaner (at least on some engines) since they run warmer, and also because the YICS system should allow the inner pair to “steal” more than the outer pair. If they’re really effectively leaner, they'll need a longer duration of a spark to ignite their charge, and of course the way to achieve that is: you guessed it, increased resistance on those inner cylinders!

A very good review of the issue of electrical resistance in ignition systems can be found at:




Although the above article references the ignition systems in ultra-light aircraft, the same concepts apply to all ignition systems.

Okay, so that's your nickel tour, and although it's not as detailed as it could be, hopefully it's enough to get you started. A good voltmeter (also called an ohmmeter) is an invaluable friend when trying to track down ignition system problems, as you must make sure that the "information" between components is actually able to travel from Point A to Point B properly, and that the individual components are, electrically-speaking, able to process and transmit the electrical information properly.

A good companion write-up to this subject and some trouble-shooting guidelines can be found at:



Ignition system components resistance specifications:

The following list also covers the resistance values of the spark plugs, plug caps, the ignition pick-up coils (which are located behind the left side round crankshaft end cover)m and the ignition coils. The resistance of the pick-up coils can be checked at their connector to the TCI box by measuring the resistance between the grey and the black wire (this checks the condition of the first pick-up coil) and then between the orange and the black wire (this is the resistance of the other pick-up coil).

NOTE: "K" is abbreviation for a thousand units, so "5K" ohms = 5,000 ohms of resistance, etc.

XJ550 models:

Pick-up coils:
650 ohms +/- 20% = 520 ohms to 780 ohms acceptable range

Ignition Coils:

Primary side (input from main wiring harness):
2.5 ohms +/- 10% = 2.25 ohms - 2.75 ohms acceptable range

Secondary side (spark plug wires, without their end caps):
11K ohms +/- 20% = 8,800 ohms - 13,200 ohms acceptable range

Spark plug caps:
10K +/- 20% = 8,000 to 12,000 ohms per cap acceptable range

Spark plugs:
0 ohms per plug

XJ650 models:

Pick-up coils:
1980-81 XJ650 Maxim and Midnight Maxim: 700 ohms +/- 20% = 560 ohms to 840 ohms acceptable range
1982 XJ650RJ Seca (non-yics engines): 700 ohms +/- 20% = 560 ohms to 840 ohms acceptable range
1982-84 XJ650 Maxim: 650 ohms +/- 20% = 520 ohms to 780 ohms acceptable range
1982 XJ650RJC Seca (yics engine): 650 ohms +/- 20% = 520 ohms to 780 ohms acceptable range
1982-83 XJ650 Turbo: 120 ohms +/- 20% = 96 ohms to 144 ohms acceptable range

Ignition Coils:

Primary side (input from main wiring harness):
2.5 ohms +/- 10% = 2.25 ohms - 2.75 ohms acceptable range

Secondary side (spark plug wires, without their end caps):
11K ohms +/- 20% = 8,800 ohms - 13,200 ohms acceptable range

Spark plug caps:
5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range

Spark plugs:
0 ohms per plug

XJ700 air-cooled models:

Pick-up coils:
120 ohms +/- 20% = 96 ohms to 144 ohms acceptable range

Ignition Coils:

Primary side (input from main wiring harness):
2.7 ohms +/- 10% = 2.43 ohms - 2.97 ohms acceptable range

Secondary side (spark plug wires, without their end caps):
12K ohms +/- 20% = 9,600 ohms - 14,400 ohms acceptable range

Spark plug caps:
1985 N/NC models: 5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range
1986 S/SC models: 10K +/- 20% = 8,000 to 12,000 ohms per cap acceptable range

Spark plugs:
1985 N/NC models: 0 ohms per plug
1986 S/SC models: 5K ohms per plug

XJ700-X water-cooled models:

Pick-up coils:
120 ohms +/- 20% = 96 ohms to 144 ohms acceptable range

Ignition Coils:

Primary side (input from main wiring harness):
2.7 ohms +/- 10% = 2.43 ohms - 2.97 ohms acceptable range

Secondary side (spark plug wires, without their end caps):
12K ohms +/- 20% = 9,600 ohms - 14,400 ohms acceptable range

Spark plug caps:
10K +/- 20% = 8,000 to 12,000 ohms per cap acceptable range

Spark plugs:
1985 XN/XNC models: 0 ohms per plug
1986 SX/SXC models: 5K ohms per plug

XJ750 air-cooled models:

Pick-up coils:
650 ohms +/- 20% = 520 ohms to 780 ohms acceptable range

Ignition Coils:

Primary side (input from main wiring harness):
2.5 ohms +/- 10% = 2.25 ohms - 2.75 ohms acceptable range

Secondary side (spark plug wires, without their end caps):
11K ohms +/- 20% = 8,800 ohms - 13,200 ohms acceptable range

Spark plug caps:
1981-83 models: 5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range
1984 RL models: 10K +/- 20% = 8,000 to 12,000 ohms per cap acceptable range

Spark plugs:
0 ohms per plug

XJ750-X water-cooled models:

Pick-up coils:
120 ohms +/- 20% = 96 ohms to 144 ohms acceptable range

Ignition Coils:

Primary side (input from main wiring harness):
2.7 ohms +/- 10% = 2.43 ohms - 2.97 ohms acceptable range

Secondary side (spark plug wires, without their end caps):
12K ohms +/- 20% = 9,600 ohms - 14,400 ohms acceptable range

Spark plug caps:
10 +/- 20% = 8,000 to 12,000 ohms per cap acceptable range

Spark plugs:
5K ohms per plug

XJ900RK, RL, N, FN, and F models:

Pick-up coils:
120 ohms +/- 20% = 96 ohms to 144 ohms acceptable range

Ignition Coils:

Primary side (input from main wiring harness):
original coils, marked CM12-20: 2.7 ohms +/- 10% = 2.43 ohms - 2.97 ohms acceptable range
replacement coils, marked CM12-09 or CM12-10: 2.5 ohms +/- 10% = 2.25 ohms - 2.75 ohms acceptable range

Secondary side (spark plug wires, without their end caps):
original coils, marked CM12-20: 13.2K ohms +/- 20% = = 10,560 ohms - 15,840 ohms acceptable range
replacement coils, marked CM12-09 or CM12-10: 11K ohms +/- 20% = 8,800 ohms - 13,200 ohms acceptable range

Spark plug caps:
RK and RL models: 5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range
N, FN, and F models: 10K +/- 20% = 8,000 to 12,000 ohms per cap acceptable range
S and SH models: 15K +/- 20% = 12,000 to 18,000 ohms per cap acceptable range

Spark plugs:
RK and RL models: 0 ohms per plug
N, FN, and F models: 5K ohms per plug

XJ1100 models:

Pick-up coils:
120 ohms +/- 20% = 96 ohms to 144 ohms acceptable range

Ignition Coils:

Primary side (input from main wiring harness):
2.5 ohms +/- 10% = 2.25 ohms - 2.75 ohms acceptable range

Secondary side (spark plug wires, without their end caps):
11K ohms +/- 20% = 8,800 ohms - 13,200 ohms acceptable range

Spark plug caps:
5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range

Spark plugs:
0 ohms per plug

XS1100 models:

Pick-up coils:
720 ohms +/- 20% = 576 ohms to 864 ohms acceptable range

Ignition Coils:

Primary side (input from main wiring harness):
1.5 ohms +/- 10% = 1.35 ohms -1.65 ohms acceptable range

Secondary side (spark plug wires, without their end caps):
15K ohms +/- 20% = 12,000 ohms - 18,000 ohms acceptable range

Spark plug caps:
5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range

Spark plugs:
0 ohms per plug


The resistance across each pair of lead wires (at the TCI) should be checked as shown in the following video……note that resistance valves specified in the service manual is for measurements taken at 70-F, and as the coils heat up, their resistance values will change, and the use of a hair dryer or heat gun to warm up the coils is simple way to see if values go way out of range as the coils heat up:


Resistance values at 70-F are as follows:

120 ohms +/- 10% for all XJ650 Turbo models, XJ700 all models and XJ750-X models, XJ900RK, RL, N/FN, and F models, and XJ1100 models.

650 ohms +/- 20% for all XJ550 models, 1982-84 XJ650 Maxim, 1982 XJ650RJC Seca (Canadian, yics-engine), and all XJ750 models.

700 ohms +/- 20% for all 1980-81 XJ650 models and 1982 XJ650RJ (non-yics engine) models.

720 ohms +/- 20% for all XS1100 models

NOTE: if both coils are out of specifications, suspect a pinched or shorted black ground wire, which is a shared ground for both of the pick-up coils on most models. It is very unlikely (although not impossible, especially in a case of improper jump-starting, etc.) that BOTH pick-up coils would expire at the same time!

A simple test to see if the coils are working, at all is to place a voltmeter (preferably an analog unit) across the Grey or the Orange wire to the Black wire. Energize the system and watch for voltage pulses as you rotate the reluctor past the pickup. This can be done by hand or with the starter.......we'd recommend using the hand method so that the pulses are slow enough to see. These "pulses" are what the TCI "black box" counts and interprets when "deciding" when to fire the ignition coils.

NOTE: the orange lead wire is the trigger wire for the #1/#4 ignition coils, while the grey lead wire is the trigger for the #2/#3 ignition coils.


The -82310 part number is the left side ignition coil and is for cylinders #1/4 spark plugs. It has the solid orange (ground) wire and the red-with-white-tracer-stripe (hot) wire input leading to it.

The -82320 part number is the right side coil and is for cylinders #2/3 spark plugs. It has the solid grey (ground) wire and the red-with-white-tracer-stripe (hot) wire input leading to it.


Factory Yamaha coils need to "see" a total load resistance on the secondary side (the "going-to-the-plugs" side of the coil) of around 20-30K ohms (ohms being a measure of electrical resistance). Electrical resistance depends on a number of factors: wire size, type of material, length of material, ambient temperature, etc. etc. All readings are specified at 70-F.

In any case, all factory XJ coils and wires combined---BUT WITHOUT THE CAPS OR PLUGS ATTACHED---have the following primary and secondary resistance ranges:

For all XJ models except XJ700, XJ750-X, and XJ900 models:

Primary (input from TCI): 2.5 ohms +/- 10%
= 2.25 ohms - 2.75 ohms acceptable range

Secondary (output to spark plugs): 11K ohms +/- 20%
= 8,800 ohms - 13,200 ohms acceptable range

For all XJ700 and XJ750-X models:

Primary (input from TCI): 2.7 ohms +/- 10%
= 2.43 ohms - 2.97 ohms acceptable range

Secondary (output to spark plugs): 12K ohms +/- 20%
= 9,600 ohms - 14,400 ohms acceptable range

For all XJ900RK, RL, N, FN, and F models:

Primary (input from TCI): 2.7 ohms +/- 10%
= 2.43 ohms - 2.97 ohms acceptable range

Secondary (output to spark plugs): 13.2K ohms +/- 20%
= 10,560 ohms - 15,840 ohms acceptable range

For all XS1100 models:

Primary (input from TCI): 1.5 ohms +/- 10%
= 1.35 ohms -1.65 ohms acceptable range

Secondary (output to spark plugs): 15K ohms +/- 20%
= 12,000 ohms - 18,000 ohms acceptable range


The firing order is 1-2-4-3 for all XJ engines.


http://www.xj4ever.com/dyna coils install.pdf


Original TD (Tokia-Denso) and aftermarket NGK SPARK PLUG CAPS are available in a variety of styles and configurations. All plug caps include their weatherproof upper and lower rubber end boots.

Okay, before we get going, let's quickly review a little bit about the original Yamaha COILS, PLUG WIRES, PLUG CAPS, and the SPARK PLUGS used on these bikes:

Factory ignition systems are designed to operate properly with a total system resistance on the secondary side (the "going-to-the-spark-plugs" side) of the coils of around 20-30K ohms (ohms being a measure of electrical resistance). Electrical resistance depends on a number of factors: wire size, type of material, length of material, age of material, ambient temperature, etc. etc. In any case, most factory XJ coils and wires combined---BUT WITHOUT THE CAPS OR PLUGS ATTACHED---are specified to have a resistance of around 11K ohms, +/- 20%, at 68-degrees Fahrenheit. Please see the complete list of specifications in the "COILS" section above.

Plug WIRES on factory coils are non-replaceable, at least not without a bit of surgery. Suffice it to say that if your coils measure out of specs for resistance (as described above), they're junk and should be replaced, either with another factory coil or a pair of the HCP245 Dyna aftermarket coils.

We do offer an NGK plug wire in-line splicer (HCP2789) that will allow you to cut off and remove a bad factory wire and replace it with a length of our aftermarket plug wire.

The original spark plug wire resistive CAPS---mistakenly called "boots" by some people---are the hard plastic insulators that fit onto the spark plug threaded stud, and accept the plug wire from the coil on their other end via a simple "twist-on" method------yes, the plug wire end of the cap has a metal screw that bites into and "screws" onto the end of the plug wire, penetrating the plug wire inner metal core and making a mechanical connection.

Plug caps use a small internal ceramic resistor, and the resistance of each cap should be checked with an ohmmeter on a periodic basis. Caps that are +/- 20% resistance from specified levels are considered bad, and should be replaced:

5K +/- 20% = 4,000 to 6,000 ohms per cap acceptable range:
all XJ650 models
1985 XJ700 air-cooled models
all 1981-84 XJ750 (except XJ750RL) models
all 1983-84 XJ900RK and RL models
all XJ1100 models
all XS1100 models

10K +/- 20% = 8,000 to 12,000 ohms per cap acceptable range:
all XJ550 models
1986 XJ700 air-cooled models
all XJ700-X water-cooled models
all XJ750-X water-cooled models
1984 XJ750RL models
all 1985-up XJ900F, N, and FN models

15K +/- 20% = 12,000 to 18,000 ohms per cap acceptable range:
all XJ900S and SH models

Spark plug "boots", typically seen on automotive engine plug wires, are usually only a protective (insulating) rubber cover........there is no internal resistor (as with plug "caps") since there is an internal direct-connection from the spark plug wire to the spark plug top terminal stud. Automotive ignition systems take care of system resistance via the spark plug itself, and the spark plug wire (which is resistive, unlike on these bikes, which use non-resistive wire), and thus do not rely on a resistive plug "cap" to regulate the resistance of the ignition secondary circuit. Yamaha chose to go with non-resistive plug wire, resistive plug caps, and (on most models) non-resistive spark plugs....thus allowing the resistive plug "cap" to handle the entire resistive load for the secondary circuit.

So don’t resist (ha-ha), go ahead and read this and become an electrical-resistance genius:


If you would like to keep your (otherwise) good condition original plug caps, you can rebuild the ones which are marked TD-131, TD-135, and TD-140 (the TD-133 caps can be rebuilt, but we do not have the correct 5K ohm resistor to fit it, and the TD-134 caps cannot be rebuilt) by replacing the internal RESISTOR CORE, the thin resistor SPRING SEAT DISC, and cleaning the TENSION SPRING and the screw-in brass cap PLUG.



Always remember, that if you replace an original resistor with a core of lesser-value resistance, you should "make-up" the difference in electrical resistance via the use of resistor plugs.


NOTE: you should never gap nor re-gap the high-performance Iridium spark plugs! All of the gapping information below pertains only to standard spark plugs. On Iridium plugs, always leave their gap "as-is" when they are removed from their box and for evermore!!

On all engines equipped with non-Iridium plugs, you can experiment with plug gaps to try and increase performance slightly. Typically, opening up the gap slightly improves high-load and high-rpm performance; in fact, the ability to run larger plug gaps is the [/i]real[/i] reason why you should consider using high-output ignition coils…..they have the extra voltage needed to successfully bridge larger plug gaps than the stock coils do.


The stock gaps are given below. One user reports better overall performance on their XJ700-X (water-cooled engine) with the gap set at .048” (rather than the stock .028”).

0.60 - 0.70mm (0.024 - 0.028")
- all XJ550 engines
- all XJ700-X and XJ750-X engines

0.70 - 0.80mm (0.028 - 0.032")
- all XJ650 engines
- all XJ700 air-cooled engines
- all XJ750 air-cooled engines
- all XJ900 engines
- all XJ1100 engines

The recommended service interval for spark plugs calls for their replacement every 7,500 miles. Spark plugs should be torqued to 14 foot-pounds on all XJ models except the water-cooled XJ700-X and XJ750-X models, which only require 12 foot-pounds of torque.


Original SPARK PLUGS on all XJ-series bike were the NGK brand. Although many other brands of plugs can be cross-referenced to the originals, NGK plugs offer both value and performance that is quite satisfactory, in both the original stock performance configurations, and in replacement standard or high-performance, platinum-tipped IRIDIUM IX resistive design plugs. All non-resistor plugs have zero ohms resistance, while all resistor plugs.....those with the letter "R" in their part number.....have a resistance rating of 5K (5,000) ohms.

Although spark plugs are pretty cheap (and thus it's not to hard on the wallet to replace plugs with new ones as part of an ignition system troubleshooting routine), if you want to actually check their condition, here's how you do it:


On all engines equipped with non-Iridium plugs, you can experiment with plug gaps to try and increase performance slightly. Typically, opening up the gap slightly improves high-load and high-rpm performance; in fact, the ability to run larger plug gaps is the [/i]real[/i] reason why you should consider using high-output ignition coils…..they have the extra voltage needed to successfully bridge larger plug gaps than the stock coils do.


The stock gaps are given below. One user reports better overall performance on their XJ700-X (water-cooled engine) with the gap set at .048” (rather than the stock .028”).

0.60 - 0.70mm (0.024 - 0.028")
- all XJ550 engines
- all XJ700-X and XJ750-X engines

0.70 - 0.80mm (0.028 - 0.032")
- all XJ650 engines
- all XJ700 air-cooled engines
- all XJ750 air-cooled engines
- all XJ900 engines
- all XJ1100 engines

The recommended service interval for spark plugs calls for their replacement every 7,500 miles. Spark plugs should be torqued to 14 foot-pounds on all XJ models except the water-cooled XJ700-X and XJ750-X models, which only require 12 foot-pounds of torque.

Spark plug knowledge you can use:

- Reading spark plugs:




- Spark plug heat ranges and plug etiquette:


- Believe it or not, there’s actually quite a bit of information on the proper installation and use of spark plugs that is not generally known or appreciated. A few minutes review can prevent a world of hurt, aka Don’t Lose Your Head!:







Yamaha (thankfully!) used a TCI (which stands for Transistor Controlled Ignition) system on all XJ-series bikes to control the coils, timing, spark advance, etc. A TCI unit is an "early" version of the now-common electronic control systems that are used on virtually all modern vehicles of almost every type, and even these early versions are completely maintenance-free and very rarely cause problems...........which is a good thing, because original TCI boxes are no longer available new.

When engine performance problems develops, many people immediately suspect that the cause may be within the "black box" workings of their TCI unit, which is unlikely. The factory service manual gives "instructions" for diagnosing TCI problems, and it basically says "test every other possible cause for your problem and if no other cause for the problem exists, only then should you "suspect" TCI failure, but before you buy a replacement, first try to find a known, working TCI unit from a similar bike and plug it in on the problem bike, and see if the problem goes away............"


There are three main problems that TCI units succumb to after years of reliable service:

1) bad solder joints on some of the internal components (known as "cold solder joints") result in the component pieces coming loose from the circuit board, and thus they can no longer perform their function reliably (or at all).

2) component failure......a blown-up transistor, a burned circuit trace, etc. This situation can develop if you have a short-circuit in your electrical system, or hook up your battery or jumper cables incorrectly, etc. TCI units do not like "big blue sparks" in the electrical system (except at the spark plugs, of course!).

3) another common failure of these units occurs if the TCI is continuously grounding the ignition coil (i.e. its output driver is shorted). You can verify this situation with an ohmmeter with the following tests:

- disconnect the 2-pin plug at the ignition coil and measure from the orange or grey wire to the chassis. You should see very high resistance. This should be pretty close on both the working and non-working channels.

- if you read a few ohms of resistance or less, then the TCI is bad. A shorted driver will also make the ignition coil run very hot and may ruin the coil.

4) dirty external terminal connections.

Bad solder joints can be repaired by someone who is skilled at that sort of diagnosis and repair, and even individual circuit components can be replaced, but it's tough to find someone in the modern world of "pitch-and-plug" skill-sets who actually has the skill and patience to do this type of work. Yamaha gave absolutely "zero" electrical specifications for checking the condition of the TCI units, besides the afore-mentioned "check everything else first" type of diagnosis.

But you can perform a simple set of tests to determine whether your TCI unit is good or not, without having a second, known good unit to install in place of the suspect unit. Although these instructions were written for XS owners, the exact same thoughts apply to the TCI units on the XJ-series of bikes:


The above is stolen, borrowed or even plagiarized from Randy Rado's site before it went away. It does require an analog meter as digital multi-meters do not show the swing of the needle that is required to test it.

"Using a voltmeter set on 12VDC, connect the positive meter lead to the Orange or Grey pick-up coil lead at the TCI. Connect the negative meter lead to the black (negative) lead at the TCI. Turn on the ignition. Voltage should come right up to about 10 - 11VDC. Crank the ignition and observe the meter. Look for a wide voltage swing during cranking. A strong swing indicates that the pickups and TCI are working OK and your trouble is between the TCI and the plugs. Possibly a bad ballast resistor, bad coil, bad plug cap or just corroded connections. Repeat this test for both Orange and Grey coil leads."

Remember that the Red wire with the white tracer stripe should always be hot with the key on. The TCI unit grounds the gray and orange wires from the ignition coils. The ignition coils fire when the TCI interrupts the ground.

The tricky part is the TCI un-grounds the gray and orange if there is no signal from the pick up coils for a few seconds. This is to protect the coils from overheating if the key is on and the engine isn't running. So unless you check the Red/white wire to gray (or orange) really quickly, you might get false readings or a mis-diagnosis of the true nature of the problem.

All of the XJ-series TCI units are of the "4RO" style as described in the above article.

Video here:


And if the above isn't enough, if you feel the need to get medieval with your TCI unit, well, then it doesn't get much better than this:


and this:


And for those who just can't resist a good Resistor (or transistor), here you go:


and Holy Dark Mother of Fibre, don't try this at home kids!:


One of the peculiarities of the TCI is the need to have at least one ground path for each secondary coil winding when checking for spark, or the TCI could (more like will) be damaged. For that reason you should never have more than one spark plug wire disconnected at any one time while cranking, and check for spark one plug at a time by grounding the plug to the head.

In situation where you would want all plugs out…….for example, compression testing of the engine……then it is recommended that the TCI be unplugged from the main harness before testing is undertaken.

By the way, the TCI needs a minimum of about 10VDC to operate......and while the starter will spin the engine over like mad with low voltage, the TCI falls on its face at less than 10 volts.....which can lead to all sorts of confusion when a battery low-voltage condition occurs!


Well, in order for your engine to start and run, you’ve got to have fuel, spark, and enough engine compression.

The following article is THE authoritative testing procedure if you suspect a no-start situation is due to ignition system issue. Obviously, it assumes that:

a) you are getting fuel into the carbs (verify this by loosening one (or all of them, but one at a time!) of the carb bowl drain screws and see if some fuel leaks out. If so, you got fuel! If not, you’ll need to tackle this issue and figure out why.

b) you have good engine compression. If you’re not sure, you’ll need to perform a compression test and verify that then engine is making enough compression.

c) your battery should be fully charged:

While the starter is engaged (but before the bike starts), the battery voltage should be 9.5 volts or greater. If not, then this signals either a bad battery, very dirty or weak electrical connections, or it could be an incredibly problematic starter motor (not likely; it's probably the battery!).

A low voltage during cranking will prevent the ignition coils from getting enough voltage to charge themselves enough to deliver a good spark to the plugs.



NOTE: when swapping engines (or oil pans/sensors) beware of these differences:

- the HCP700 (analog gauge) sensor is a N.C. (normally closed) style switch when the oil level is at a correct level, while the HCP701 (computer dash) sensor is a N.O. (normally open) switch when the oil level is at a correct level. Thus these sensors, If swapped between bikes, will not give proper signaling to their warning lights or read-outs!


Do you have a speedometer or tachometer that has a “Mexican jumping bean” needle?

- the first thing to suspect is the drive cable (for all speedos and mechanically-drive tachos). Take the cable off from the bike, inspect the end fittings for wear, inspect the wire for any fraying, etc. and replace if necessary. Otherwise, the both the wire cable and the internal of the outer sheath can be cleaned with a solvent such as aerosol brake or carb cleaner. The wire cable should then be lubed generously with fresh motor oil (we like the Castrol brand 5W40 synthetic motor oil), drive chain lube, or penetrating cable lube, and then as it is re-inserted into the outer sheathing, spun around by hand to distribute the lubricant, and then the cable should be hung vertically for a few moments to allow excess lube to drip out. A small smear of moly grease at the bottom end finishes your cable lubrication procedure.

- if the cable is okay and lubed properly, then the problem is internal to the drive head within the gauge,
and requires a surgical procedure which may or may not solve the problem (these are 35+ year old gauges, after all). Here is how to do a basic cluster breakdown and service:

Although shown on an XJ550 Seca model, the basic process is the same on all clusters:


XJ750 Maxim and XJ750 Seca clusters are illustrated here:

http://www.xj4ever.com/gauge cluster breakdown.pdf

And the XJ700 style gauges are shown here:

http://www.xj4ever.com/repairing your 700 gauges.pdf

Actual gauge mechanism servicing:


Electronic tachometer testing and servicing:


NOTE: we strongly recommend that you do not remove (nor try to do so) the needle assembly from the gauge unit……it is clocked into a certain position, and removing the needle shaft almost always results in a non-operational gauge upon re-assembly.

150mph speedo retrofit:





http://www.xj4ever.com/repairing your 700 gauges.pdf


http://www.xj4ever.com/crimping my style.pdf




How to properly add a wire splice:



If you are doing a custom project, and just have to do away with some electrical devices, here's some basic wiring diagrams that you can use to guide your efforts:









OEM turn signal system FLASHER and SELF-CANCELLER RELAY. In order to design a "self-canceling" turn signal system, Yamaha chose to use a simple but very different style turn signal Flasher than what is used in almost all other vehicle applications. Of course, the unique design of this flasher unit makes it, let's say, "pricey" to say the least! However, if you want your self-canceling feature to work then you'll have to use this original flasher. NOTE: many aftermarket mechanical or solid-state flashers will not function (at all) in place of the original flasher, and even the ones that do (see below) will disable the use of the self-canceller feature from operating.

Also, if you substitute LED bulbs in your turn signals for the standard incandescent bulbs, then the stock flasher (which is mechanical) will not see enough of an electrical load to be able to flash correctly, if at all. In such a situation, the stock flasher is not defective, it is just designed to operate at a much higher voltage draw than LED lights provide, and you will need to replace the stock flasher with an aftermarket solid-state flasher. NOTE: the use of most aftermarket, solid-state flasher relays will defeat the self-canceller feature of the original system.

Identification: The FLASHER is contained in a large, rectangular black hard-plastic "box" housing, and has the following 3 wires connected to it: a solid brown wire, a brown wire with a white tracer stripe, and a yellow wire with a green tracer stripe. This applies to all models except XJ700 and XJ750-X models.

The SELF-CANCELLER UNIT is a rectangular, sealed, rubber-coated box with 6 wires coming out of it into a connector: a solid tan wire, two (2) white wires with a green tracer stripe, a yellow wire with a green tracer stripe, a yellow wire with a red tracer stripe, and a white wire with a red tracer stripe.

By the way, the self-canceller operates off both time AND distance measurements to determine when it should cancel the flashers.....a minimum of 10 seconds time and 150 meters (about 400 feet) distance. BOTH criteria must be met before the canceller releases the signal flasher:


NOTE: the signal system is designed so that it will still operate if the self-canceller module fails; of course, in such a situation, you will have to cancel the signals manually (by pushing straight “in” on the thumb lever after it has returned to the center position). To diagnose problems with your signal system, you should follow these steps:

1) unplug the self-canceller from the main harness.
2) identify the following wire on the main harness side of the plug: white with green tracer stripe wire and the solid black wire.
3) using a volt/ohm meter set on the ohms x 100 range, probe those two wires and then spin the front wheel. The ohms reading should shuttle back and forth between 0 and infinity
4) if the above is good, now identify the yellow with red tracer stripe wire. Hook one lead of your ohm meter to it, and the other to a good chassis grounding point. Now, with the flasher switch on the handlebars OFF (center position), the meter should read infinity. With the lever moved to either the left or right signal engagement position, the ohm meter should read 0 ohms.

If the signals work properly when the self-canceller is disconnected from the system, then you know that the flasher relay, the bulbs, and the handlebar switch circuit (inside the control switch on the handlebars) is okay. If the signals won't operate properly, even with the self-canceller removed from the system, then it may be a problem within your control switch itself, the flasher relay, the signal bulbs, wiring, etc. The movement of the thumb lever fully to one side, AND THEN RELEASING THE LEVER, should:

a) allow the lever to return to center, and
b) keep the turn signals ON (flashing) in whichever direction you had chosen, until either:

i) the self-canceller, if plugged in the system, cancels the flashers, or......
ii) if the self-canceller is un-plugged from the system, then the flasher will not cancel until you push "in" on the lever, while the lever is in the center position.

Having to hold the lever fully over to the left or right position is an indication that the internal contacts (within the switch housing) may be wonky. There is a "two-armed" contact that can get bent, or, the slider contacts may have gotten dirty and/or the solder connections to the slider contacts have broken or become loose:




The first link above has a good image of the copper contact "arms" that can get bent, and will thus no longer make contact with the brass "button" contact on the bottom of the pivoting lever arm (one button contact on each side of the lever arm), while the second link has some good images of the slider assembly.

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