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Stop, now, what’s that sound?
Everybody look what’s going down…….
- Buffalo Springfield

Yes, the joy of trying to describe a noise in text................and where it might be coming from.

* Don't quit yer' whining:

Yamaha used a straight cut primary gearset, which is very strong and a bit noisy. Typically heard as a whistle or a whine - some have compared it to a turbo sound. The RPM where it's audible will vary a bit from bike to bike, but it will make the noise in neutral and is pretty much not dependent on load.

GM also used straight-cut gears on some of their late 60’s muscle cars in the M22 “rockcrusher” 4-speeds. You can hear that same distinctive (some would call it almost musical…….) transmission whine even over the engine sounds in this video:

Of course, if you prefer your gear whine without bothering to use a clutch, try this:

* Whistling or chirping noises are some of the hardest to identify as to their source. Here's a couple of tricks:

Quick verification: take the plugs out. If the noise goes away then it's compression. If the noise remains, it's something else. "Something else" can be a number of things, but large vacuum leaks tend to give off whistling and/or chirping sounds...........

* Popping noise or what sounds like a bearing knock:

Possible it's a bad bearing, but more than likely it's a leaking exhaust gasket (hold a tissue around the exhaust joints and see if it flaps in the breeze.......)

* A bag-'o-marbles-in-a-tin-can sound:

This is typical of a starter clutch issue.....see the STARTER CLUTCH section below. Not a good thing........

* Clutch chattering:

If the sound comes only when the clutch lever is squeezed, then check the throw out bearing. It's a radial needle bearing that is pulled by the rack and pinion inside the clutch cover, and when it goes bad it will squeal like a stuck pig.

* metallic sounds from the top end of the engine:

XJ550’s can make a particular type of “quiet” rhythmic, metallic knocking sound from the top end, which will disappear as rpm’s increase………..this is typically caused by a primary chain (inside the engine) which can “flop” around a bit at low rpm’s due to low oil pressure (oil pressure is used to tension this chain). It’s nothing to worry about.

A "tap-tap-tap" in the upper end may or may not be something to worry about; if it’s s “sharp” metallic sound…..that could be a cam bearing or cam cap problem. Both the XJ650 and air-cooled XJ750 engines had a factory TSB (Technical Service Bulletin, or in other words, an internal "warning" to their dealers) regarding slightly loose tolerances for camshaft end-play on these engines. It's a regular ticking sound that increases along with the engine speed, and is most easily heard from the right side of the head when the engine is hot. Generally, it is safe to ignore it, as no harm is being done. The camshaft end-play is not so large as to cause any damage.

If it’s just a soft, sewing-machine like tick-tick-tick sounds, then that is probably just the valves happily clicking away through their proper clearances. By the way, the lack of this tick-tick-tick sounds is not a good thing: tight valves make no sound, and tight valves are a quick way to ruin your engine!


The periodic checking and replacement of these valve clearance shims is one of the most over-looked of all the regularly scheduled maintenance tasks on these bikes.......and with predictably negative results.

The proper operating clearance of these shims (or, in the case of XJ700-X and XJ750-X engines, the Adjusting Pads) is necessary for both the maximum power output of your engine and the longevity of your camshaft and engine's life. Allow these clearances to get too small---which they will, over time---and you run the real risk of burning the valves (especially the exhaust valve) and that's just Not A Good Thing. An engine that runs poorly, stalls, or is very hard to start after it is fully warmed up, points to dangerously decreased valve clearances. Of course, if the shim clearances are too large, your engine will be down on compression and power throughout all rpm ranges.

And if the clearances vary from their specified ranges significantly in-between different cylinders, then it makes any attempt at engine synchronization---via the adjustment of the carb "synch screws"---meaningless and a sure way to reduce both the power output and the lifetime of your engine.


Think about what happens if YOU were a valve.......you get pushed around by the cam bucket/shim assembly, which gets pushed around by the CAM LOBE. The lobe is tapered so that it starts pushing at you at a certain point in the cam (engine) rotational cycle, and doesn't STOP pushing you around until much later in the rotation, at which time DUE TO SHIM CLEARANCE, you get a little break before the whole cycle starts anew.

Big bully, that cam lobe is…..

If there is little to no valve shim-to-cam-lobe clearance, then the cam lobe STARTS bullying onto you sooner, and ends its pushing LATER in each rotational cycle.....you (the valve) spend more time being lifted off your seat, due to the lack of clearance. Not only do you remain open longer during the compression stroke, you also don't get as much "face time" (ha-ha, a pun.....) with your valve seat, and that face time is when you get to cool down, and the lack of it really burns you up.......literally. You don't get to release your heat to the valve seat during that fully-closed time, and it's the equivalent of being cast into that ever-burning lake of fire and brimstone......

Not only that, but remember that there is a moment when both valves are open (called overlap" in camshaft-speak), and if the intake valve is OPENING SOONER, and the exhaust valve is CLOSING LATER (both due to being too tight, i.e. not enough clearance), then this overlap time (measured in degrees of cam rotation) is going to increase = lost compression.

And if that's not enough, the timing of valve opening and closure is what is known as cam timing, and tight valves will ADVANCE the cam timing (when the valve opening first begins in the rotational cycle), and this effects engine power in very real ways. While slightly advanced cam timing can increase engine performance, too much (or, even worse, a variable amount for each cylinder, based on differing clearances and thus different cam advance profiles for each cylinder!) makes a real mess of things. It's certainly not what the design engineers had in mind when they were tuning the engine for certain output at certain rpms......i.e. throttle responsiveness.

And finally, these engines are what are known as "interference" engines, meaning that within the cylinder, there are certain points in time when the piston and the valves occupy the same physical X, Y, Z coordinates within the cylinder (the piston at and around the TDC, the valve at and around full opening). At higher rpm's there is always going to be a little bit of valve "float", where the valve movement "lags" behind the cam lobe profile, in essence "floating" above the cam lobe profile for an instant or two, until the valve springs can overcome the momentum of the valve being rocketed off the top of the cam lobe profile. Although not an issue during the compression stroke, during the exhaust stroke if the valve is held open too long (lack of any shim clearance, or a "negative clearance" situation), the piston and valve may "interfere" with each other in decidedly unfriendly ways.

I keep referring to the LACK of shim clearance as being the major issue of concern, since that is the most common scenario......as time goes by, valve shim clearances are REDUCED due to the valve pounding its valve seat in the head (due to spring closing pressure banging the valve closed), thus forcing the seat further up into the head, thus bringing the valve stem/bucket/shim CLOSER to the cam lobe. This is the reason that periodic shim adjustment are needed, and, they are most needed on newer engines, as that is when the most valve seat recession occurs (first 10K miles or so). After that point, most of the valve seat compression is done, and valve clearances become more stable for longer amounts of time.

Of course, the opposite effects occur if shim-to-cam lobe clearances are too LARGE, the valve never opens fully, and it remains open for less time (the cam timing is retarded rather than advanced); you'll build full compression pressure, but won't be able to take advantage of it (not as much fuel entering, not enough time for exhaust gases to be pushed out). You won't be risking burning valves or having piston/valve interference issues, though.

Wow, just writing this out puts me into a cold sweat. I'm going to go check my clearances right now. A great photo journal of the valve clearance checking and replacement process for all air-cooled engines is documented at:







The procedures for the water-cooled "X-heads" can be seen at:




and here’s a useful tip:


Oh, and another bit of advice to both the inexperienced and seasoned, as well----when it comes to remove the valve shims from their buckets, please block off the cam chain passage completely with a rag or paper towels in order to prevent a "popping shim" from migrating to a place that it doesn't belong (somewhere deep inside the bowels of your engine!):


By the way, for those owners that use the molded rubber valve covers, you'll want to inspect and replace the "pressure washers" on the valve cover bolts, as those pressure washers are what actually create the pressure on the valve cover to seal the gasket. Here's the trick to making a frustrating job easier:




Finally, make sure that you set your clearances correctly; the Haynes manual has an incorrect listing for the XJ650 Seca models, don't let it fool you!:


USEFUL TIP: sometimes you’ll come across an engine that has “zero-clearance” or negative-clearance valves…..an outrageous sign of previous owner(s) neglect (and, by the way, a real smoking-gun which shows that level of neglect probably applies to everything on such a bike, so you’d better double-check every critical system on such a bike twice!). Since there will be no “clearance” that can be measured, then there is no way to calculate what size shim(s) that you’ll need to get such valves back into spec, without first replacing the currently-installed shim with a much thinner shim (thin enough so that at least some amount of clearance begins to occur). If you can’t find an already-installed shim (on any of the other valves) that are small enough to obtain some amount of clearance on the offending cylinder(s), then we recommend that you order a variety of “very thin” shims from the list below, so you’ll have at least one size that will allow a clearance to be measured…..and then your correct size replacement can be calculated accurately. Based on experience, we would consider the 2.00mm - 2.20mm shims to be “very thin” for most engines


Basic oil change procedure explained:


When the filter housing bolt get stuck:

In case your filter housing bolt gets seized and frozen tight, here’s how to make it “take one for the team” and get it off:


Of course, with our replacement spin-on filter kit, you’ll never have that problem again! Here are the instructions and installation:

http://www.xj4ever.com/spinon kit v2.1.pdf



Which type and brand should you use? Great question! Here's a some good answers:




NOTE: Yamaha specifies the use of API "SE" or "SF" grade oil in all XJ models, but that is based on the original (at that time) automotive motor oil standards.....which, as the above article notes, are no longer valid in the current lubrication industry environment and classifications. Therefore we recommend that the oil you choose should meet or exceed the JASO "MA" duty rating, and all of the oils below exceed that standard. Do not EVER use synthetic oils unless they are specifically designed for motorcycle engines using wet clutch systems (as these bikes do use), as you will end up with a slipping clutches (both drive clutch and especially the starter clutch). Additionally, do not use "automotive" grade oils that have friction modifiers (reduced-friction additives) as these will cause the same problems.

The factory recommends the use of 10W30 oil when the outside temperature will never exceed 60-F, or 20W40 if the outside temperature is always above 40-F. Unfortunately, 20W40 oil is difficult to find anymore, but there is not an issue with using a straight 40W oil, or 10W40, 15W40, or 20W50 formulations instead.

All XJ-series engines require somewhere from 2.5 quarts to 3.0 quarts for an oil change (depending on whether the filter is replaced or not) except for the 1100 engines, which require slightly under a gallon to accomplish an oil and filter change.

- I see some metal shavings in my (oil pan, spark plug insulators, etc.). How do I tell what it’s from?


KwonP1 :
This is a very basic guide, and really only applies to metals in its pure form. Most scrapyard and commercial sources have an alloyed form of each material, meaning its mixed with other metals and some of its properties will change. Often times it may be washed with another, electroplated, chemical plated, hardened, etc. Not unusual for something that appears to be one metal is actually another --- for example, gold and silver plated objects. Another example, pure tin may snap when bent, but the common 'tin sheet' is a steel sheet with a thin layer on tin on the surface, and it does not make noises when bent (e.g. with a metal brake).

A few of my own methods:

Aluminum: is diamagnetic: this means that aluminum will not stick to a stationary magnet, but a moving magnet will induce some magnetic properties. is that is reacts with vinegar (it starts bubbling) while aluminum doesn't, so this test makes it easier to distinguish between the two.

Chrome: is usually plated on to another metal, there is decorative that can tarnish, peel and flake off, if in good condition has a mirror finish, and is pretty soft. Then there is hard chrome often used on load bearing parts (axles, shafts, bearings, etc.) that is matte silver in color, can be very glossy in texture, will not be scratched even with a hardened steel sample, generally does not tarnish or corrode.

Magnesium: the best way to identify if something is solid magnesium is its price tag. Its expensive. really expensive. alternatively, small metal filings (shave off with a steel knife) will readily ignite by match or lighter flame and burn bright white. primary consumer uses would be performance engine blocks and performance car wheels (rims). In my metallurgy class we had a magnesium brake rotor from a commercial airliner laying around, and we knew about magnesium's self-reinforcing flammability once heated over its critical temperature. Needless to say, we shaved a few strips off of the rotor and took them and our oxy-acetylene torch to the lot outside the shop, and set light to it. The magnesium strips got red hot, and then combusted into an intense white flame. It left a small hole straight through the concrete and asphalt...so a word to the wise, be carefully with this stuff!!

Silver that turns black over time. the presence of ammonia in the vicinity of a metal can make it turn black. (learned this the hard way when i accidentally left steel tools in a bucket of water with some house paint in it) long term exposure to ammonia can cause pitting.

Titanium: is a tough one to identify, but again easy if you just look at the price tag, the stuff is priced more like gold! Titanium is rarely used in everyday objects, it’s found mainly in high-end products made for specialty, exotic purposes: medical, aeronautics, high end camping gear, jewelry, etc.


Can you say intake manifold bolts and exhaust port studs? Shure you can……..


"If there is not enough grip between the plunger and the roller, it can skip, causing the grinding, clacking noises you hear. I have been told by a Yamaha mechanic with over 20 years experience that it is very possible for some synthetics to greatly increase the chances that this will occur......

So this weekend I drained the synthetic out, put some cheap 20W50 in, and rode it for a little while. Then I drained the cheap oil out and put Castrol GTX 20W50 in and the starter does not malfunction anymore, not even once! I cant believe it! I guess these bikes were not made to run synthetic---I'm sticking with conventional oil from now on."

If the above solution doesn’t work, then it might be time to do the dirty deed. If you read this thread, you'll get a good idea of what challenges you're up against:


When you finally get the starter clutch assembly out of the engine and available for rebuild, we suggest that the central hub unit be inspected carefully for any damage or cracks, and replaced if needed. Here is a common problem that you need to look for (scroll down for the image of the cracked hub):


There’s only one way to repair a starter clutch that’s bad without splitting the engine cases, and it ain’t pretty:


Luckily (?), you only need to remove the lower engine case to replace the clutch:


And here she is, the prize at the bottom of the Crackerjack Box:



Valve Lapping Porn:


Engine teardown and rebuild Porn:


Bent Valves Porn:

- or, why my engine has no compression on all 4 cylinders..........


Just a quick heads-up:

- what I learned when swapping cylinder heads:


- those heat-treatment Crankshaft Blues:


- getting kinda cranky:


The large gear on the right is the primary drive gear.
The small sprocket in the center is for the cam chain.
The larger sprocket at left-center is for the alternator/starter clutch HYVO chain.

The oil pump is driven off of the clutch input shaft (the one that is driven by the primary drive).


splitting the cases, and then actually putting it all back together again without any leftover parts:


Re-sealing the cases isn’t hard to do, but you gotta be careful!

NOTE: you should review a service manual before applying this material to the engine cases, as there are certain areas (particularly around oil feed holes) that should never have sealer applied near them. See the bottom of page 2:


A video tour inside your engine. Although this features an XS/XJ1100 engine, all of the basics are the same, and it gives a pretty good explanation of how the transmission part of the "engine" operates:


Crankshaft Bearings:

Yamaha used a unique way of "sizing" their engine bearings, both for the crankshaft main journal bearings and the connecting rod big-end bearings.

The factory coded, via a series of numbers indicating a "size code", numbers onto the crankcase, the crankshaft, and the connecting rods.

The crankCASE has numbers hand-scrawled onto the upper (and possibly the lower, also) engine case(s) ---typically, behind/below the stamped pad where the engine ID number is, behind the clutch cover opening, but, in reality, could be anywhere on the case(s) --- that specifies the main bearing saddle sizes for that particular engine case:


Note that these last 2 sets of 2 numbers --- “40’ / 46” and “45 / 40” in the above examples --- are the codes used for calculating the thickness of the shims used with the middle gear drive shaft of each particular engine.

The crankSHAFT will have two grouped sets of numbers on one end. The first set of 5 numbers are the main bearing journal size numbers for that crankshaft, and the second set of 4 numbers which denote the rod bearing journal numbers for that particular crankshaft. Both sets of numbers refer to the crank journals starting at the left side of the crankshaft (the #1 cylinder side, see the last picture in the post below):


Each connecting rod also has a number that is stamped (with ink) on the rod itself, right where the upper and lower shells meet.

To calculate the correct bearing sizes to use in a particular engine, you will go through the following process:

Crankshaft Main Bearings:

The correct main bearing selection is made by subtracting the crankshaft journal number from the engine case main bearing saddle size number, for each main bearing journal position.

Connecting Rod Big-End Bearings:

The correct bearing selection is made by subtracting the crankshaft journal size number from the rod size number, for each rod/crank journal position.

For both the crank main journal bearings and the rod bearings, you will then use the numbers calculated above to realize a "bearing color" as outlined in the chart below. You would then order the correct "color" bearing for each crankshaft main journal or connecting rod big-end position:

Bearing "Color Codes":

#1 = Blue
#2 = Black
#3 = Brown
#4 = Green
#5 = Yellow

A good visual of the color marking on the bearing can be seen at:



- Crankshaft is marked 21223 2111
- Engine case is marked 34534 48 47 (note that these last 2 sets of 2 numbers --- ’47’ and ‘48’ in this example --- are codes used for calculating the thickness of the shims used with the middle gear drive shaft)
- Rods are marked 6, 4, 3, and 3

The first set of 5 numbers on the crankshaft (21223) are the main bearing journal sizes for that crankshaft, and are sequentially #1 to #5 as read. The corresponding 5 numbers scratched onto the engine case (34534) are the main journal saddle sizes for that engine and are sequentially #5 to #1 as read. For the #1 main journal position (the far left position), we would have 4 (on the engine case) - 2 (on the crankshaft) = 2. The #1 main journal bearing is a "size" 2, which is a "black" bearing.

NOTE THAT THE HAND-SCRAWLED NUMBERS ON THE CRANKCASE READS JOURNALS #5 TO #1 as you read them left-to-right, and thus in a 5/4/3/2/1 sequence for the main journal bearing sizes! They are actually "backwards" from an intuitive approach (and "backwards" from the sequence they are coded onto the crank itself), but are "correct" in spatial orientation and sequence for the top crankcase half (since they are scrawled "reverse" in relation to the crankshaft position within the crankcase).

For the #1 con-rod, using the example above, you would use the 2nd set of numbers on the crankshaft (2111), and the ink-stamped number on the rod itself. So the #1 rod is stamped as 6, and the #1 crank rod journal is 2, and 6 - 2 = 4. Thus the #1 rod was use a "size" 4 connecting rod bearing, which is a "green" bearing.

Notice that it is NOT unusual for a single crankshaft to use a variety of different "size" or "color" bearings.

NOTE: The yellow "size" bearings are used only for crankshaft main journal bearings. Rod bearings were never made nor available in the yellow "size".


Bearing Clearance Measurement:

As mentioned, bearing oil clearances are critical for engine longevity. Clearances are measured via the use of a thin, crushable plastic “bead” which is positioned between the bearing and the journal, and which is then crushed when the parts are torqued to proper specifications. The parts are then separated, and the width of the crushed plastic strips are compared against a (included) reference chart. This is a simple, accurante, yet very time-consuming task, but it must be done to insure that you engine assembly is done properly!

These measurements should be done for all bearing positions on the crankshaft main journals, the crankshaft rod journals, and all camshaft journals.


Yamaha recommends that you perform a compression test every 5,000 miles or so, and that you should record the readings, per cylinder, for future comparison and evaluation. The acceptable readings (specified at sea level) are as follows:

To do a compression test properly, you should first make sure all of your engine valves are properly adjusted to their recommended clearances, as valves that are too "tight" (not enough clearance) will allow the intake or exhaust valve to be open more than is necessary, or at the wrong time within the compression stroke cycle, thus bleeding off compression that would otherwise be developed.


Do not use thread adapters or the like on your pressure gauge, as the added volume of air space within the adapter will reduce the indicated pressure readings.

a) make sure the engine is warm (at operating temperature).

b) remove all spark plugs, and then stick the plugs back into their caps and make sure the plugs are grounded to the cylinder head (or even better, disconnect your TCI unit).

c) remove the airbox filter lid and the air filter.

d) make sure the battery is FULLY charged, and remains so throughout the course of these tests! It is actually recommended that for purposes of compression testing that the TCI be un-plugged and jumper cables to a large capacity battery (i.e. car battery) be used to make sure that the cranking speed remains pretty constant between each reading. Slow or sluggish cranking speeds will reduce the indicated compression pressure. Yamaha specifies their compression pressures at 300 rpms (which is why the battery needs to be in good shape).

e) open the throttle FULLY and keep it open during testing.

f) crank the engine over until the needle stops advancing.

g) Let the starter cool down for a minute or so, then do the next cylinder, etc.).

h) If the readings are below spec, then shoot about a teaspoon amount of motor oil into each cylinder, crank the engine over a few revolutions with the starter (to spread the oil around), and then re-test each cylinder using the above procedure.

i) compare the two results and analyze.

j) keep all of your figures, and note the date and mileage from your odometer, so you can compare the next time you take readings (every 5,000 miles or so).

The specified compression pressures should be:

XJ550 engines:
Minimum: 100 psi
Standard: 121 psi
Maximum: 135 psi
Max. variance between lowest and highest: 14 psi

FJ600 engines:
Minimum: 142 psi
Standard: 156 psi
Maximum: 164 psi
Max. variance between lowest and highest: 14 psi

XJ600 Seca II engines:
Minimum: 145 psi
Standard: 160 psi
Maximum: 167 psi
Max. variance between lowest and highest: 14 psi

XJ650 and XJ750 air-cooled engines:
Minimum: 128 psi
Standard: 156 psi
Maximum: 171 psi
Max. variance between lowest and highest: 14 psi

XJ700 non-X (air-cooled) engines:
Minimum: 128 psi
Standard: 156 psi
Maximum: 171 psi
Max. variance between lowest and highest: 14 psi

XJ700-X and XJ750-X (water cooled) engines:
Minimum: 154 psi
Standard: 159 psi
Maximum: 165 psi
Max range allowable between highest and lowest readings: 14 psi

XJ900 engines:
Minimum: 114 psi
Standard: 142 psi
Maximum: 171 psi
Max. variance between lowest and highest: 14 psi

XJ1100 engines:
Minimum: 128 psi
Standard: 142 psi
Maximum: 156 psi
Max. variance between lowest and highest: 14 psi

NOTE: for readings taken at locations that are above sea level (ASL), the following correction factors should be applied to the readings that your gauge obtains:

- 500' ASL, multiply your readings by 1.013 to get a "true" compression reading.
- 1000' ASL, multiply your readings by 1.029 to get a "true" compression reading.
- 1500' ASL, multiply your readings by 1.042 to get a "true" compression reading.
- 2000' ASL, multiply your readings by 1.060 to get a "true" compression reading.
- 2500' ASL, multiply your readings by 1.072 to get a "true" compression reading.
- 3000' ASL, multiply your readings by 1.093 to get a "true" compression reading.
- 3500' ASL, multiply your readings by 1.103 to get a "true" compression reading.
- 4000' ASL, multiply your readings by 1.126 to get a "true" compression reading.
- 4500' ASL, multiply your readings by 1.136 to get a "true" compression reading.
- 5000' ASL, multiply your readings by 1.160 to get a "true" compression reading.
- 5500' ASL, multiply your readings by 1.172 to get a "true" compression reading.
- 6000' ASL, multiply your readings by 1.196 to get a "true" compression reading.
- 7000' ASL, multiply your readings by 1.233 to get a "true" compression reading.
- 8000' ASL, multiply your readings by 1.272 to get a "true" compression reading.

Also, be aware that barometric pressure differences (during testing events separated by more than just a few hours) will cause changes in indicated compression readings. Atmospheric pressure can vary significantly over time at the same altitude, due to weather systems….you hear this on weather reports, where the forecaster is talking about “High” and “Low” pressure systems. Basically, higher atmospheric pressures translate into higher indicated compression pressures. Although it is rarely of major consequence, in order to be "dead-nuts" accurate you should also record your local barometric pressure at the time of each test. If you measured compression on a day when it was 1030mbar and observed 150psi, and then took a measurement later in the week/month/etc. when the ambient air pressure was only 990mbar, that’s an environmental air pressure difference of about 4%, and assuming nothing else had changed you would then read a 4% less compression pressure of only 144psi......

But don’t overlook the fact that the individual test gauge being used is probably the greatest variable. Some compression gauges are just not very accurate to begin with (basically, and within reason --- and just like with most tools --- the it costs the more accurate it will tend to be). Also, try to keep the hose on the gauge you are using as short as possible….the space inside the hose adds to the volume of the cylinder, as lowers the compression ratio a bit, and thus reduces compression pressures.

And in case you are interested, here are the standard compression ratios for the various engines:

XJ550: 9.5-to-1
FJ600: 10.0-to-1
XJ600 Seca II: 10.0-to-1
XJ650 (except Turbo): 9.2-to-1
XJ650 Turbo: 8.2-to-1
XJ700 air-cooled: 9.5-t-1
XJ700-X and XJ750-X water: 11.2-to-1
XJ750 air: 9.2-to-1
XJ900: 9.6-to-1
XJ1100: 9.0-to-1
XS1100 9.2-to-1

Note that the XJ650 Turbo engine has a much lower static CR than all other engines……logically so, since it has a device (the turbocharger!) that raises the atmospheric pressure of the incoming air charge. Also of note is the rather “sky-high” CR of the multi-valve Genesis engines in the water-cooled “X” engines, which is also one of the keys to their vastly increased power output.

Now Analyze This!:

1) If one or all of your cylinders are too low in pressure, it means that:

a) you did the compression test incorrectly

b) the tester gauge is inaccurate, or was not used properly.

c) your engine has piston ring, piston wall, or valve leakage problems.

d) you valve clearances are too tight, and should be adjusted, or aftermarket camshafts have been fitted that have altered the camshaft timing.

e) if a cylinder or cylinders have NO compression at all, that typically means your piston has been catastrophically damaged (i.e. a hole in the piston crown, broken piston, etc.)

f) if a cylinder or cylinders have good compression that rapidly "leaks away" (best determined by the use of a Leakdown Tester gauge as listed further below), this points to burned or otherwise problematic valves.

In order to further analyze a low-compression condition, you should squirt a small amount of engine oil into the suspect cylinders (about a teaspoon), crank the engine over for a few revolutions to spread the oil about, and then re-test those cylinders.

g) if the compression pressures RISE by a large amount after the infusion of oil, then this typically means that the pistons, piston rings, or cylinder walls are damaged or worn in some way(s). However, be aware that if you introduced a significant amount of oil into a cylinder (1 teaspoon or more) when conducting this test, a small rise in pressure may occur, and it may instead mean that your valves are the problem, since the introduction of that much oil in a small cylinder will naturally cause the compression to rise.

h) if the compression pressures do NOT rise after the infusion of oil, then this typically means that the valve seats or faces are worn, or a valve is hanging up within its guide, or your valve clearances are way too small.

i) if two adjacent cylinders (cylinders 1 and 2, or cylinders 3 and 4) have low compression, and the oil treatment produces no greater pressures, this points to a damaged cylinder head gasket, warped head, etc.

j) it can be very useful to introduce 20-30 psi of compressed air into the cylinder (thru the spark plug hole) to help identify the source of low compression: the escaping air can pinpoint the source of the leak (air hissing out of the intakes or exhaust points to valve problems, while air escaping thru the crankcase breather indicates ring-seal issues).

Of course, many other situation may cause low cylinder compression, including valves that are out of adjustment (too tight, thus holding a valve slightly open all the time, losing compression), cracked pistons, cylinders, or cylinder heads, but those situations are the not all that common.

2) If one or all of your cylinders are too HIGH in pressure, it means that:

a) you piston domes (tops) and/or the cylinder head combustion chamber have a significant accumulation of carbon upon them, which should be cleaned via some type of chemical treatment or engine dis-assembly and manual removal methods. Note that higher cylinder pressures caused by such build-up may be "masking" or hiding other problems that might cause LOW cylinder pressures, such as worn rings, etc.

b) your engine has been fitted with aftermarket, high-compression pistons, or has had the cylinder head "shaved".

NOTE: high cylinder pressures are NOT a good thing, as they tend to blow out head gaskets and can cause accelerated piston, piston ring, or bearing wear.

You can also test for piston ring and cylinder wall condition by performing a "leak-down" test, which consists of forcing a measured amount of compressed air into a cylinder, and then seeing how long before this air "leaks" out of the combustion chamber and down into the crankcase (past the ring seal):


NOTE: be aware that some of the ultra low-priced gauges that are typically advertised on eBay, etc. can be quite un-reliable in their readings, and may regularly indicate a false (low) compression reading.


Pistons and piston rings are not ordered until AFTER engine teardown and cylinder wall diameter, taper, and other critical measurements and conditions are inspected, and the determination is made concerning what the final cylinder size is needed (standard bore, 1st oversize, etc.).

Only then does the purchase of the appropriate sized pistons and/or ring sets commence. Pistons are then measured for their actual size (as opposed to their "supposed-to-be" advertised size), and only then does engine boring occur, to allow for and result in the proper piston-to-cylinder clearances. Piston rings are then fitted and sized to the actual finished cylinder dimensions before installation.

ANY MACHINIST OR SHOP THAT DESCRIBES TO YOU A PROCESS OTHER THAN THE ABOVE, PLEASE TAKE YOUR ENGINE AND BUSINESS ELSEWHERE, as they are planning on "cutting corners" on your engine rebuild and such actions will cost you dearly in the performance and longevity of your rebuilt engine.

- All original and aftermarket piston rings are "directional"....the top and second ring are designed to be installed in a certain orientation. Check your service manual for the proper installation procedures. Most factory oversize rings have their oversize dimension stamped into the top ("up") surface of the ring; standard sized rings typically do not have any such markings. 2nd (center) rings are always installed with their wider, "scraper" edge towards the bottom of the piston:



- All original and aftermarket piston rings must be sized to the finished bore dimensions by filing the end gap to achieve proper specified clearance (end gap). Failure to do so can result in seized rings. Most air-cooled engines run "choked" cylinders.....the cylinder bore is smaller at the bottom of the bore and larger on top (after the cylinder reaches operating temps, the bore stabilizes). This "choke" is also known as bore taper and is critical.

When measuring your cylinder, take your readings with a t-gauge or cylinder bore dial indicator at the BOTTOM of the choke. This will give you your tightest ring gap reading. Once you determine which rings to buy, you'll need to hand-check each one by pushing it to the bottom of the choke to measure your ring gap. If it's too tight, you'll need to file the ends of the gap to open up the clearance. This can be done hand with a small flat file, but it's a much wiser idea to buy a ring gap filer------it does a much neater and far more accurate job. It is also recommended that a proper size Flex Hone be run down the bore PRIOR to fitting the rings......the cross-hatch finish that the flex hone creates will give new rings a nice bore pattern with which to seat.

- a good tutorial on piston ring break-in procedures can be found here:


If you want to de-carbon your piston crowns, valves, or combustion chambers, then a 50/50 mix of automatic tranny fluid and acetone (careful, extremely flammable!) left overnight on the carboned areas will help to soften and loosen the carbon, allowing easier removal with a brass brush.

By the way, here's the main reason you don't want to run lean over an extended period of time:


A holed piston. Notice how it's right where the plug fires (the hottest point anyway, and made ultra-hotter by a lean fuel condition).

And all the inside dope on cast versus forged piston is nicely summarized right here:





- A great pictorial guide to replacing the tach cable drive o-ring and seal can be seen at:


- and here's a good write-up on changing the alternator shaft oil seal on a later model Yamaha (XJ600 Seca II).....although the procedure is not exactly the same on the 1980's XJ-series engines, it's close enough to show the entire process, and with very good pictures:


And here is the procedure shown on an XJ700 engine, other XJ engines of this era are very similar in procedure:


NOTE: in some situations, you can use the following technique to remove larger oil seals that would otherwise require case-splitting to remove. All large oil seals have a metal inner structure that you can (very carefully!) drill into and then pry out:



a/k/a preventing a good-night “kiss” between your valves and piston crowns….

Make absolutely sure that your cams and chain are clocked correctly to your crank, or your motor might easily become toast. Although there is no substitute for having a factory or aftermarket service manual in performing this procedure, here are the basic ideas involved:



NOTE: in the truest hot-rod tradition, people sometimes inquire as to camshaft specifications and interchange. We have compiled the following information for your reading pleasure:

XJ550 Maxim:

Intake Lift: 6.80mm
Exhaust Lift: 6.80mm

Duration: not given

Overlap: not given

XJ550 Seca:

Intake Lift: 7.80mm
Exhaust Lift: 7.10mm

Duration: not given

Overlap: not given

XJ650 all models except Turbo:

Intake Lift: 8.50mm
Exhaust Lift: 7.80mm

Intake opens 34-degrees BTDC
Intake closes 58-degrees ABDC

Exhaust opens 66-degrees BBDC
Exhaust closes 26-degrees ATDC

Overlap: 60-degrees

XJ650 Turbo:

Intake Lift: 8.50mm
Exhaust Lift: 7.80mm

Intake opens 28-degrees BTDC
Intake closes 48-degrees ABDC

Exhaust opens 53-degrees BBDC
Exhaust closes 23-degrees ATDC

Overlap: 51-degrees

XJ700 non-X models:

Intake Lift: 8.80mm
Exhaust Lift: 8.30mm

Duration: not given

Overlap: not given

XJ700-X and XJ750-X models:

Intake Lift: 7.50 - 7.70mm
Exhaust Lift: 7.35 - 7.55mm

Duration: not given

Overlap: not given

1981-83 XJ750 models:

Intake Lift: 8.80mm
Exhaust Lift: 7.80mm

Duration: not given

Overlap: not given

XJ750RL models:

Intake Lift: 8.80mm
Exhaust Lift: 8.30mm

Intake opens 38-degrees BTDC
Intake closes 58-degrees ABDC

Exhaust opens 56-degrees BBDC
Exhaust closes 26-degrees ATDC

Overlap: 74-degrees

XJ900RK and RL models:

Intake Lift: 8.75mm
Exhaust Lift: 8.25mm

Intake opens 38-degrees BTDC
Intake closes 58-degrees ABDC

Exhaust opens 66-degrees BBDC
Exhaust closes 26-degrees ATDC

Overlap: 64-degrees

XJ1100 and XS1100 models:

Intake Lift: 8.80mm
Exhaust Lift: 8.80mm

Duration: not given

Overlap: not given

SOME TANTALIZING THOUGHTS: although we have not----and do not know of anyone who has---there may be opportunities for performance gains via cam-swapping between different models. Here is what we can say with surety:

a) XJ550 Maxim and Seca cams can be swapped between these engines (but not with any of the 650-up engines). The 550 Seca cams are "hotter", they have more lift, and probably also have increased duration and possibly overlap.

b) all XJ650 (except, perhaps, for the Turbo models), XJ700 non-X, and XJ750 model cams will interchange. Here's the lift variances between them:


* 650 models (except Turbo): 8.50mm
* 700 non-X models: 8.80mm
* 1981-83 750 models: 8.80mm
* 1984 XJ750RL models: 8.80mm


* 650 models (except Turbo): 7.80mm
* 700 non-X models: 8.30mm
* 1981-83 750 models: 7.80mm
* 1984 XJ750RL models: 8.30mm

Since the cam lift durations and overlap specifications are not available for all models, we can only (for now) guess what those differences are; however, it would be reasonable to speculate that the 700 non-X and XJ750RL cams are the "hottest" of the bunch, followed by the 1981-83 750 cams, and lowest on the totem pole would be the 650 non-Turbo cams.

Although camshaft design and swapping is a real black art, as not only are lift, durations, and overlap issues involved, there's also cam-timing considerations as well as the interaction between all those factors and cylinder size, air flow into and out of the cylinders, etc. to account for.

Please note that in order to correct (or enhance) other design parameters or issues, it is sometimes best to swap out ONLY the intake OR the exhaust cam (rather than both)......so much depends on the engine and bike in question, the intended usage, rpm power range desired, etc.

Like we said, a black art....... Remember, "hotness" in camshafts, just like beauty, is in the eye of the beholder, and it depends on whether your definition of "hot" is "low-end power", "all-around power", "high-end screamer", or some other variation of the above.

If anyone has any experience with cam swaps on these engines, please let us know what you did, and how it worked out!!

c) XJ700-X and XJ750-X cams do not interchange with any other XJ-series engines.

The Yamaha Genesis engines, not just another purdy face:


d) XJ900RK and RL cams----these we just don't know about. We BELIEVE (but cannot assure you) that they will interchange with all XJ650, XJ700 non-X, and XJ750 engines. If so, they are probably the "hottest" cams available.

e) XJ1100/XS1100 cams do not interchange with any other XJ-series engines.


The secret life of cam chain tensioners can be explored further at:




Yamaha specifies that for the manual-tensioner models, the adjustment should be checked and adjusted (if necessary) every 5,000 miles. Automatic tensioners should never need checking, as they should adjust themselves, well, automatically!

Here's some tips on how to go about doing this adjustment properly:





A brief musical interlude here, folks. Since this question comes up fairly often, we'd like to offer the following pointers when considering or performing an engine swap into your bike:

XJ550 models:

Being a chain-driven bike (unlike all the 650cc-up models, which are shaft-driven), swapping the larger engines into the XJ550 frames is basically a Job for Jesus, or those with similar amounts of time and talents (and, lots of fabrication money, too!). There's simply no easy way to get from "here" to "there".

The most likely donor engine would be from a FJ600 or similar model.

XJ650 models:

Since one of the most popular engine swaps is putting an XJ750 engine into an XJ650 frame, we offer the following tips and guidelines regarding what issues you might expect to have to deal with in regards to this popular conversion. Also note that XJ750 Maxim/Midnight Maxim engines mount differently than XJ750 Seca engines, due to the lack of the rubber engine mounting insulators on XJ750 Seca crankcases.

* when putting an XJ700 (air-cooled) engine into a XJ650 Maxim, Midnight Maxim, or RJ Seca frame, please observe the following changes:

- observe the same procedures and cautions as applies to using the XJ750 Maxim/Midnight Maxim engines. The air-cooled XJ700 engines use rubber insulators to mount them to the frame, but you will need to retain the XJ650 engine mounting hardware (XJ700 engine mounts are in a different relative position in the frame).
- it is unknown which airbox boots you will need to use.
- the XJ650 Maxim/Midnight Maxim use the same style shifter assembly as an XJ700 engine, but differ from the XJ650RJ Seca shifter assembly.
- have to convert tachometer to an electrically driven version on all 1980-81 XJ650 Maxim, Midnight Maxim, and 1982 XJ650RJ Seca models.
- the XJ700 oil level sender can be used.
- will need to use XJ700 carbs and intake manifolds.
- need to retain XJ650 exhaust system.
- need to retain XJ650 wiring harness, except for the pick-up coils sub-harness. The pick-up coils on the XJ700 engines are different. Need to use the XJ700 TCI box.
- when using an XJ700 engine, be aware that there is a slight gearing difference----the XJ700 models have a slightly different gear ratio, also, even though they share the same size rear wheel as the Maxim. Thus there will be a difference in the acceleration of the bike, depending on which donor engine is used.
* it would be advisable to use the XJ700 swingarm assembly and driveshaft.
* one note of interest: the XJ700 engines, although of the same basic design as the XJ650 and XJ750 engines, are actually a much more "heavy-duty" unit, employing some of the XJ650 Turbo and XJ900 internal engine refinements and upgrades, as well as using a stronger, 6-spring clutch system, and also a much larger and stronger u-joint and driveshaft.

* when putting an XJ700-X or XJ750-X (water-cooled) engine into a XJ650RJ Seca frame, please observe the following changes:




* when putting an XJ750 engine into a 1980-81 XJ650 Maxim or Midnight Maxim frame, please observe the following changes:

- have to convert tachometer to an electrically driven version.
- the original XJ650 oil level sender needs to be retained (unless the engine is from a 1983 750 Maxim or Midnight Maxim).
- the 650 shifter side cover and all internal components needs to be retained, unless you want to keep the 750 Seca style shifter. The 750 Maxim style shifter may not work.
- the engine mounting hardware for the XJ750 engine will need to be used (no rubbers on XJ750 Seca; XJ750 Maxim used the same basic hardware. Use the XJ650 front upper frame brackets when using a Maxim engine; the XJ750 Seca frame brackets when using a Seca engine).
- will need to use XJ650 airbox boots.
- will need to use XJ750 carbs (or re-establish the XJ650 carbs to XJ750 specs).
- need to retain XJ650 exhaust system.
- need to retain XJ650 wiring harness, except for the pick-up coils sub-harness. The pick-up coils on the XJ750 engines are different. Need to use the XJ750 TCI box.
- when using an XJ750 engine, be aware that there is a slight gearing difference----the XJ750 Seca used a 18" rear wheel, while the XJ650 Maxim models used only a 16" rear wheel, and thus middle drive gear ratios are slightly different inside the tranny. The XJ750 Maxim models have a slightly different gear ratio, also, even though they share the same size rear wheel as the Maxim. Thus there will be a difference in the acceleration of the bike, depending on which donor engine is used.

* when putting an XJ750 engine into a 1982-83 650 Maxim frame, please observe the following changes:

- the original XJ650 oil level sender needs to be retained (unless the engine is from a 1983 750 Maxim or Midnight Maxim).
- the 650 shifter side cover and all internal components needs to be retained, unless you want to keep the 750 Seca style shifter. The 750 Maxim style shifter may not work.
- the engine mounting hardware for the XJ750 engine will need to be used (no rubbers on XJ750 Seca; XJ750 Maxim used the same basic hardware. Use the XJ650 front upper frame brackets when using a Maxim engine; the XJ750 Seca frame brackets when using a Seca engine).
- will need to use XJ650 airbox boots.
- will need to use XJ750 carbs (or re-establish the XJ650 carbs to XJ750 specs).
- need to retain XJ650 exhaust system.
- need to retain XJ650 wiring harness.
- when using an XJ750 engine, be aware that there is a slight gearing difference----the XJ750 Seca used a 18" rear wheel, while the XJ650 Maxim models used only a 16" rear wheel, and thus middle drive gear ratios are slightly different inside the tranny. The XJ750 Maxim models have a slightly different gear ratio, also, even though they share the same size rear wheel as the Maxim. Thus there will be a difference in the acceleration of the bike, depending on which donor engine is used.

* when putting an XJ750 engine into a 1982 650RJ Seca frame, please observe the following changes:

- have to convert tachometer to an electrically driven version.
- the original XJ650RJ oil level sender needs to be retained (unless the engine is from a 1983 750 Maxim or Midnight Maxim)
- the 650RJ shifter side cover and all internal components are the same as those in a XJ750 Seca engine. The 750 Maxim style shifter may not work.
- all engine mounting hardware for the XJ750 Maxim engine will need to be used (no rubbers on Seca engines; an XJ750 Seca engine uses the same mounting hardware as the XJ650RJ Seca, except for the front upper frame brackets, the XJ650RJ Seca frame brackets should be used. If using an XJ750 Maxim engine, you'll need to be creative.............
- will need to use the XJ650 airbox boots.
- will need to use XJ750 carbs (or re-establish the XJ650 carbs to XJ750 specs).
- need to retain the XJ650RJ exhaust system
- need to retain the XJ650RJ wiring harness, except for the pick-up coils sub-harness. The pick-up coils on the XJ750 engines are different. Need to use the 750 TCI box.
- when using an XJ750 engine, be aware that there is a slight gearing difference----while both the XJ650RJ Seca and the XJ750 Seca models used a 18" rear wheel, the XJ750 Maxim models used only a 16" rear wheel, and thus the middle drive gear ratios are slightly different inside the tranny on some engines. Thus there will be a difference in the acceleration of the bike, depending on which donor engine is used.

* when putting an XJ900 engine into a XJ650 Maxim, Midnight Maxim, or RJ Seca frame, please observe the following changes:

- it can be done: http://xjbikes.com/Forums/viewtopic/t=29398.html

The same guidelines as generally outlined in the XJ700 engine swap should be observed.

* when putting an XJ1100 engine into a XJ650 Maxim, Midnight Maxim, or RJ Seca frame, please observe the following changes:

- put down the tools and the torch and back s-l-o-w-l-y away from the bike.
- 1100 engines are vastly different than the other XJ650/700/750/900 engines in design, style, size, etc., and attempting to put one of these engines into the smaller frames is likely to be a complete custom job. No other information is available. It would be wise to consider buying an XJ1100 model bike, and riding that, rather than trying to transplant just the engine.....

XJ700 air-cooled models:

Most of the engine-swap modifications in regards to the XJ650 engines above will apply, and recall that the XJ700 engines are rubber-mounted. However, due to the unique frame style and engine mounting positioning, you will need to use the XJ700 frame mounting brackets and hardware.

Please note that we have not attempted such a swap, and welcome further experience from those who have completed such as transplant for any additional insights.

XJ700 or XJ750 water-cooled models:

Although it should be possible to put an XJ-series air-cooled engine into the water-cooled frame, there will be many significant engineering challenges involved, as the XJ700-X and XJ750-X frames are unique enough that many difficulties will present themselves.

1981-83 XJ750 air-cooled models:

Most of the same consideration would apply as outlined in the XJ650 Section, just reversed. With the exception of the engine-mounting issues (rubber mounts on Maxim models, solid mounts on Seca models), all XJ750 air-cooled engines are basically identical to each other.

XJ750RL and XJ900 models:

No information is available on using the smaller XJ650/700/750 engines in the XJ750RL or 900 frame, although theoretically it should work.

Of course, XJ550 and XJ1100 engines will not fit into the XJ750RL or XJ900 frames without extensive efforts and modifications.

XJ1100 models:

Much like the XJ550 models, these engines are rather unique in a verity of ways, and thus preclude swaps with their smaller XJ-cousin engines. XS1100 engines should work, but this is not an area in which we have any definitive experience.

Unfortunately, we have no good advice if this is your goal!:

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