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SECTION K:
STEERING/SUSPENSION:
--Front Suspension: Front suspension Overview.
FRONT SUSPENSION:
FORK TUBE PARTS OVERVIEW:
Your front suspension is called on to do a lot of different tasks, sometimes all at the same time: steering and braking are the two most critical ones that come to mind. Thus the proper operation and integrity of your front forks, and all their parts and pieces, is vital to the proper operation, handling, and safety of your bike. And worn front forks are the primary reason why your front tires wear out quickly, or in an uneven pattern.
Although your front forks are pretty simple devices....a spring, inside a fluid-filled tube, that serves to soak up road imperfections while maintaining positive-yet-smooth road feel and control....there are quite a few items that need attention and periodic replacement in order to get the proper lifetime and performance out of your system.
We offer a variety of OEM and aftermarket products and tools needed to properly maintain and service your forks and keep them firmly planted on the road beneath you.
NOTE: The process of rebuilding your forks seems mystical and difficult to many first-timers, mainly because all of the internal parts are normally hidden from view.....and thus the "fear of the unknown" takes over. The fork mechanisms on most of the XJ-series bikes are really pretty simple, and the entire process of removing your forks from the bike is more time-consuming and involved than the actual re-building procedure. HOWEVER, this is one procedure that we strongly recommend that you have a factory or aftermarket service manual at-the-ready, because there are certain diagrams, specifications, and various "tricks of the trade" that you'll want to know about and follow when doing fork surgery.
Forks on these bikes generally fall into one of two categories: simple and more-difficult. The simplest forks are the ones that are not encumbered by any additional "enhancements", such as air-assistance or anti-dive features. Here's the scorecard:
SIMPLE: XJ550 Maxim, XJ550 Seca, XJ650 Maxim and Midnight Maxim, XJ650RJ Seca, and XJ700 non-X.
SIMPLE-PLUS: due to the air-assist function, these forks have a few additional parts (mainly o-rings) that must be attended to, but again, these forks could just as easily fall under the "simple" category above: 1982-83 XJ650 Maxim, XJ650 Turbo, XJ700-X, XJ750-X, XJ750 Maxim and Midnight Maxim, and XJ1100 models.
INVOLVED: due to both their air-assist and anti-dive functions, these forks are the most difficult to work on.....mainly due to the addition of the anti-dive function, which introduces quite a few additional parts into the internal fork mechanism. You will definitely want a service manual handy while working on these forks, and pay very close attention to the order and orientation of all the small parts during dis-assembly: XJ750 Seca and XJ900RK Seca models.
The following discussion has some very good pointers, tips, and photographs that detail the fork rebuild process on a 1981 XJ650 Maxim model (one of the "simple" fork systems), and is a good point of reference to help you decide whether the task is something that you wish to attempt yourself or leave to a qualified shop:
http://xjbikes.com/forums/index.php?threads/8355
and
www.youtube.com/watch?v=iO8Lv6a-2Cw
And thanks to user Tabaka45 for his expose of the XJ700 fork system with this great visual review of the procedures needed for rebuilding these forks, which can be seen at:
http://www.xjbikes.com/forums/threads/fork-seals-85-xj700n-picture-heavy.78389/
A slightly more complicated type of forking system can be found on the XJ750 Seca and XJ900RK models, due to the use of the anti-dive system. An XJ750 Seca fork system goes under the knife, here:
http://xjbikes.com/forums/index.php?threads/18730
and
http://xjbikes.com/forums/index.php?threads/41895
and owner "Alive" also has two great image-documentaries in regards to these more "complicated" fork systems. This first one shows the XJ900 (with the anti-dive system) while the second link shows the guts on the later XJ900 models (without the anti-dive system). Note that these images can also be used as a guide for any model front forking system that use the lower bushing on the chrome fork tubes:
http://xjbikes.com/forums/index.php?threads/44997
and
http://xjbikes.com/forums/index.php?threads/4067
while this photo-journal details the secret, inner workings of the "anti-dive" units found on XJ750 Seca and XJ900RK Seca models:
http://xjbikes.com/forums/index.php?threads/1860
And finally, for all you XJ750 Seca owners, here's the secrets to that funny and unique "oil lock valve assembly" used only on these models, and the proper orientation of all of those special washers:
http://xjbikes.com/Forums/viewtopic/p=159288.html
and
http://xjbikes.com/forums/index.php?threads/41895
And these incredible 3-D renderings of the inner workings of a forking system gives a great visualization of the internal components (it is based on the 1982-83 XJ650 Maxim forks):
and
http://xjbikes.com/forums/index.php?threads/29616
While many people may simply need to replace the OIL SEAL, SEAL CLIP, AND DUST BOOT (sometimes called a DUST WIPER"), we also recommend that whenever you have your forks apart, that you also replace the upper CAP BOLT CIRCLIP or SNAP RING, the cap bolt O-RING or GASKET, the fork oil drain screw GASKET, the damper rod retaining bolt SEAL, and, on air-fork-equipped models, the AIR VALVE O-RINGS.
Replacing these items now, while the forks are apart, can help prevent leaks and problems from developing down the road.
On high-mileage bikes, you should also replace the metal slider bushings, taper spindles, and other items.
Almost all forks usually require the use of a DAMPER ROD RETAINING TOOL to hold the damper rod in place while the lower damper rod retaining screw (in the bottom of the lower fork tube) is being loosened or tighten; otherwise, the damper rod will spin and freely and make removal and installation difficult if not impossible.
While the basic servicing and rebuilding of your forks is not a specialized skill, it can be somewhat confusing and daunting to people who have never performed such a task before. Since the procedures vary (sometimes greatly) between the different model bikes, we can give no real instructions or recommendations besides this: refer to your factory or aftermarket service manual for the proper procedures and techniques, and if you don't already have such a manual, please purchase one!
And here’s a couple of other good tips for exceptional fork rebuilding success and performance:
http://www.motorcycleproject.com/text/stiction_tuning.html
and:
http://www.motorcycleproject.com/text/shucking.html
The general layout of your forks (some models have more or less pieces than others), from the very top of the UPPER (also called the inner or chrome) TUBE moving downwards, is as follows. Note that the items underlined are the ones that we strongly recommend replacing during a fork rebuild procedure.
- Top Cap (rubber or plastic)
- Snap Ring, sometimes called a Stopper Ring
- Cap Bolt
- O-Ring for cap bolt
- Spacer (if used)
- Upper Spring Seat (if used)
- Fork Spring
- Damper Rod, with a plastic piston ring in the head
- Damper Rod Rebound Spring
- Oil Lock Valve Assembly (XJ750 Seca)
The following items may need replacing on high-mileage or neglected (dirty oil) bikes, as these items wear quickly if the fork oil was not refreshed regularly and thus was allowed to accumulate grit and abrasive particles:
- Taper Spindle
- Metal Slide Bushing #2, a split-ring bushing on the bottom of the chrome tube, not used on all models.
Air-assisted front forks (1982-3 XJ650 Maxim and Turbo, all XJ750, XJ900RK, and XJ1100 models) also included some or all of the following parts. Note that the items underlined are the ones that we strongly recommend replacing during a fork rebuild procedure.
- Schrader Valve(s) and their protective screw-on Caps.
- O-Rings for the schrader valve(s)
- Air joints (used on XJ650 Turbo, 1982 XJ750 Maxim, XJ900RK, and XJ1100).
- Cushion Gasket for air joint
- O-Rings internal to the air joints.
- Air Hose that connects the air joints.
- O-Rings for the end fittings of the air joint connecting hose.
- Stopper Ring on models using air joints.
Additionally, all XJ650 and XJ750 Midnight Maxim models, and XJ1100 models, had upper tube covers, their related guides and associated gaskets.
The LOWER (outer) FORK TUBE is populated as follows. Note that the items underlined are the ones that we strongly recommend replacing during a fork rebuild or seal replacement procedure.
- Dust boot
- Oil Seal Clip
- Oil seal Washer (XJ750 Seca, XJ900)
- Oil Seal
- Oil seal Spacer (XJ750 Seca, XJ1100)
- Fluid drain plug and gasket
- Damper rod retaining bolt and gasket
- Fork Oil
The following item may need replacing on high-mileage or poorly-maintained bikes:
- Metal Slide Bushing #1, a split-ring metal bushing near the top of the lower tube, just below the oil seal.
Finally, as part of any fork system service you should take the time to check the fork tube alignment.....an often over-looked part of fork system maintenance:
FORK TUBE ALIGNMENT CHECKING:
One feature of front fork systems that is typically overlooked is assuring that the two fork tubes are properly aligned with each other........that they are precisely spaced apart from each other, and also exactly aligned with each other in their "rake angles", and not "twisted" in relation to each other. Hitting large objects or deep holes with the front wheel, dropping the bike, slight bending or fatigue of the steering crown or lower bracket, or any other sort of injuries can result in fork tubes that are not perfectly in synch with each other, and that can cause both annoying and dangerous steering, handling, and braking problems.
Therefore it will be worth your while to check your fork tube alignment periodically, especially after you've had them out for a rebuild.......this will be the most time-efficient opportunity you'll have for this procedure, since it requires removal of the front wheel, headlight, and other assorted front-end components.
Although the following step-by-step guide was written for BMW owners, the same techniques and guidelines will apply on your bike:
http://w6rec.com/duane/bmw/fork/title.html
If you choose not to go through the above process, you can perform the following "poor-man's" fork alignment techniques as described in the following sections:
http://xjbikes.com/forums/index.php?threads/16145
and
http://xjbikes.com/forums/index.php?threads/9323
and
http://www.motorcycleproject.com/text/stiction_tuning.html
and
http://www.xjbikes.com/forums/threads/dropped-bike-need-help.97887/#post-533302
and a good video:
Listed in the following sections you will find our complete list of fork tube rebuild and service parts, arranged BY BIKE MODEL. The description of what each individual fork component part is, and its characteristics, is first review immediately below, and then the list of items by model follows.
UPPER (INNER) FORK TUBES AND PARTS:
Chrome Inner Fork Tubes:
ift3) Reproduction UPPER (INNER) (chrome) FORK TUBE, exactly replaces bent or rusted and pitted original tubes. Beautiful hard-chrome plating will last as long as original.
All fork tubes are precision made from centerless ground, cold-rolled steel tubing, and are then machined to proper tolerances and specifications as original. All inner tubes will fit either the left or right side. Stock length tubes are listed below. Shorter or longer length tubes are available by special order, but are non-returnable or refundable, and must be inquired about directly with us specifying the length desired.
NOTE: Used upper (inner) chrome fork tubes should always be checked for straightness using V-blocks and a run-out gauge (a local machine shop should be able to do this for your inexpensively), or using a professional quality straight-edge, or roll the tubes along a known flat surface such as a 30" x 12" wide piece of 1/4" thick plate glass (you can buy a cheap piece of scrap plate glass at Home Depot, etc.). Regardless of what anyone tells you, do NOT attempt to straighten bent tubes; they must be replaced!
Also, you should carefully inspect these chrome tubes for RUSTING or PITS in the area where the fork tube slides through the lower fork tube seal area. If there is only very minor surface rusting in this area, it may be possible to polish it out; however, if the rust has pitted or eaten into or below the surface of the metal, then you will need replace the tubes, as pitting in this area will very quickly chew up any new oil seals, and you'll have leaking seals again in no time! A good image of the type of damage that you need to check for can be seen (one the 2nd page) over at:
http://xjbikes.com/forums/index.php?threads/42966
Inner Tube Gaiter Boots:
Although not originally used on any XJ-series bikes, these accordion-pleated thick rubber boots fit into the area between the bottom of the steering underbracket and the top of the lower (outer) fork boots, covering and protecting this area from damage, while providing an "old-school" or cafe-racer type look. They are retained to the chrome tube itself (at their top end) via spring clips, and to the top of the lower fork tube via metal screw-clamps.
For a great visual of how these boots appear when installed properly, see the images at:
http://xjbikes.com/forums/index.php?threads/16019
Inner Tube Top Cover/Cap:
The very top part of your fork tube is rubber or plastic cap, that serves to seal the chrome inner tube from dirt and moisture, as well as providing a decorative look.
Inner Fork Tube Cap Bolt Circlip, Snap Ring, or Stopper Ring:
These rings, located at the very top of the chrome legs, underneath the top Cap/Cover, are what hold all the rest of the internal goodies in. They are usually pretty corroded after years of inattention, and it is recommended that they be replaced during any fork renewal process. Be careful when removing these items, they are under spring pressure!
Inner Fork Tube Cap Bolts and Related:
This is the rather solid upper "plug" that retains the innards of the fork tube (the spring sits just below it). Some models may incorporate an o-ring onto this cap bolt; other use a gasket below it. Although these cap "bolts" normally don't wear out, their corresponding o-rings or gaskets should always be replaced. Some models with air-adjustable forks have the air valve threaded into this cap bolt, and the o-ring around that air valve should also be replaced during a fork service or rebuild. Always use a liberal coating of pure silicone grease (HCP1714, HCP28407, or HCP20861) when installed these o-rings onto their cap bolts.
Cap bolts that are retained via a circlip (all XJ550 models, all XJ650 models (except Turbo), and the XJ750 Seca models) should have the circlip replaced. All other models use a threaded cap bolt that screws into the top of the fork tube, and these threads inside the fork tube should be inspected carefully and cleaned up if signs of deterioration or rust, etc. are noted.
HINT #1: the area where the CAP BOLT seals (at the top of the inner fork tubes) is very susceptible to rust from water accumulation and migration into this area. Rust and pitting in this area will not allow the upper cap bolt o-ring or gasket to seal properly.....a real problem! BE SURE TO INSPECT THIS AREA THOROUGHLY WHEN YOUR TUBES ARE APART. For proper oil and air sealing abilities (on those models equipped with air-assisted forks), you want this area to be as perfectly smooth as is possible.
If there is only surface rust, you can polish it away on fork tubes that use non-threaded cap bolts (all XJ550 models, all XJ650 models (except Turbo), and the XJ750 Seca models) using either bristle-wire brush HCP10222 or HCP10223, or our HCP9955 cylinder hone, chucked into a drill, and then follow-up with some 600- and 800-grit FINISHING PAPERS (these items are listed further below in the FORK TOOLS section).
Models using threaded fork cap bolts (XJ650 Turbo, all XJ700 models, all XJ750 models, XJ900RK, and XJ1100 models), should use the butterfly brush HCP10223, chucked into a drill,on the threaded portions and finishing paper on the smooth area above the threads.
If there are DEEP PITS in this area on the non-threaded style fork tubes, you can try polishing them out using the above method; however, if they have eaten into or below the surface of the metal, then you will either need to "rebuild" the surface (using JB Weld or some type of gel Super Glue formula to fill in the depression, and then sanding and/or honing any "high spots" back down to level).
It's always a good idea to use a strong smear of pure silicone grease (HCP1714, HCP28407, or HCP20861) on the top edge of the cap bolts after they are installed; this will help to seal that area as much as possible from water migration into the fork tubes and contaminating the fork oil.
HINT #2: the surfaces where the DAMPER ROD PISTON RING seals (along the entire inner diameter of the inner fork tubes, below the top cap bolt) is also prone to rust from water absorption and accumulation in the fork oil (another great reason to change the fork oil regularly!). Rust and pitting in this area will not allow the damper rod upper plastic piston ring to seal properly.....another real problem! BE SURE TO INSPECT THIS AREA THOROUGHLY WHEN YOUR TUBES ARE APART (a strong flashlight and good eyes are needed, as it will be a "looking down the barrel of a rifle" type of view). For proper oil management abilities and thus fork function, you want this area to be as perfectly smooth as is possible.
If there is only minor surface rust, you might be able to polish it away using our HCP9255 cylinder hone with the 400-grit stones (listed further below in the FORK TOOLS section) attached to a long extension.
If there are PITS in this area, there is no real cure for them, and the fork tube should be replaced.
Inner Tube Fork Springs:
Top-quality aftermarket progressively wound FRONT FORK COIL SPRINGS don't just "restore" the performance to your front forks, they actually improve it over the original equipment. Spring and suspension technology has come a long way in the 30 years since the XJ model bikes were designed and built, and our line of performance front coil springs will not only get rid of the sags and "mush" in your front end, but will give your bike a crisper, more controllable and predictable ride and handling quality due to their superior design, engineering, and manufacturing.
Original coil springs are what are known as "dual rate springs"........they have one fixed spring rate until a certain level of compression is reached, and then a firmer, stiffer rate (stronger resistance to compression) takes over (soft, soft, soft, soft, boom! stiff, stiff, stiff.......).
Replacement springs are what are known as a "progressive rate springs".........meaning that as the load on them increases, they get progressively firmer (softest, softest, soft, less soft, firm, firmer, firmer, really firm), rather than the "all or nothing" transition that takes places with the stock springs. Progressive rate springs tends to give both a smoother, less harsh ride, as well as increasing the performance of the front suspension during enthusiastic driving and the suspension action that it creates.
One pair of front springs does both front forks. Please note that some models will require the use, re-use, modification of the original, or the fabrication of the front spring spacers (and some models do not require the use of spacers at all).
NOTE: the more tightly coiled area of your fork springs (whether original or aftermarket) should be towards the TOP of the fork tube.
Inner Fork Tube Spring Spacers, Rebound Springs, and Spring Seats:
Used along with the coils springs, these various pieces allow for the proper pre-load and spring placement within the upper fork tube. Note that not all models used spring spacers.
Inner Tube Metal Slider Bushings:
These split-ring bushings fit over into a recess at the bottom of the inner chrome tube, and along with the lower tube slider bushing, serves as a both a tube guide and absorbs the majority of the side loading of the inner tube as it passes through the lower tube. If the fork oil hasn't been changed regularly, grit and moisture in the oil eventually wear down these slides, and thus require their replacement.
Inner Fork Tube Damper Rod:
Called a "compression cylinder" in Yamaha-engineering-speak, this precisely machined tube manages the oil flow within the fork system via oil bleed holes and passages. The top "head" of this damper rod rides within a flanged area of the upper (inner) fork tube and is also the lower spring seat for the coil spring, while the bottom of this rod is internally-threaded and bolted to the bottom end of the lower (outer) fork tube----and thus this rod is what actually makes the mechanical connection and physically "joins together" the upper and lower fork tubes.
HINT: check your the damper rod for straightness using a run-out gauge or a straightedge (or the edge of a machine-cut piece of flat glass).
The damper rod head has a plastic split-ring "piston ring" that should be inspected and replaced during a fork rebuild.
Inner Fork Tube Taper Spindle:
This oddly-named part is actually a tapered metal bushing that surrounds the lower shaft of the damper rod. If your taper spindle shows signs of wear (flat spots, gouges, scoring, etc.) then it should be replaced.
Inner Fork Tube Air System Parts:
Air Joint O-Rings:
These rubber o-rings provide and air-tight seal among the various component pieces used in air-assisted fork systems. These seals and o-rings should always be replaced during a fork rebuild procedure. And always use a generous coating of pure silicone grease (HCP1714, HCP28407, or HCP20861) when installed these o-rings onto their cap bolts.
Air Inflation Valves and O-Rings:
NOTE: the top caps that are used on all of the air valves listed below are NOT the same as those used on tire valves, as the ones used on the fork air valves are much shorter.
Inner Fork Tube Retaining Hardware:
Your chrome fork tubes (properly called the "inner" fork tubes) are held to your bike via the upper and lower steering brackets. The upper bracket is called the "crown bracket" and your handlebars bolt to this bracket, while the lower bracket is called, quite logically, the under-bracket. The under-bracket has the large diameter stem that goes up through the steering neck tube (that is part of the frame), and within that tube are the steering Neck (or "Head") Bearings. This stem is then bolted to the crown bracket after it has emerged from the top side of the frame steering neck tube.
The inner fork tubes are located in round bores on both sides of the upper crown bracket and the lower under-bracket. These bore are "split" and via proper tightening of the special Cinch Bolts, the proper tension is applied to firmly locate the fork tubes to the rest of the bike.
HINTS:
a) there may be oxidation on the triple tree clamps so it might be necessary to clean the inner diameter of these upper and lower bracket clamp bores using a rotary tool with a brass wire brush wheel.
b) do NOT grease or lubricate the inner diameter of these upper and lower bracket clamp bores or put any anti-seize or other protective coatings inside these clamps, as such products will impair the effectiveness of their grip.
Crown Bracket Inner Fork Tube Retaining Hardware:
For the upper (crown) bracket, the various cinch bolts, washer, and nuts that retain the fork tube to this bracket.
Under-bracket Inner Fork Tube Retaining Hardware:
For the lower (under) bracket, the various cinch bolts, washer, and nuts that retain the fork tube to this bracket.
LOWER (OUTER) FORK TUBE PARTS:
Dust Wiper Seals:
ft1) OEM and aftermarket lower fork tube Dust Wiper Seals will stop grit and moisture from entering the lower tube cavity and chewing up the oil seals. These dust wiper seals are the things you see at the very top of the lower fork tube.
Oil Seals:
ft1) OEM and aftermarket lower fork tube Oil Seals will stop those leaks and restore the performance to your front suspension and braking system. We offer three different grades of seals to satisfy everyone's needs:
a) OEM original equipment double-lip rubber seals provide the same quality and life expectancy as the originals. Although these are not the least expensive seals, no one ever went wrong with using original manufacturer products. Oil seals come with the internal tension spring when they were originally equipped as such.
NOTE: all oil seals install with the sharp, tapered "point" of the oil seal internal wiper lips pointing "down", so that these lips can wipe the oil from the chrome tube as it exits the lower tube.
b) Standard grade aftermarket double-lip BLACK OIL SEALS are the same or better quality than the OEM seals, but normally at a better price.
c) Premium grade aftermarket seals are a significant development in fork seal technology and feature a specially designed lip and spring tensions that result in a much lower sliding friction between the seal and the fork tube. Lower friction prevents un-wanted fork movement resistance from occurring, for instance, when initially entering a corner, or braking. Ideally, you want the inner forks to move smoothly and without any "choppiness" past the lower tube seal, rather than a "starting and stopping" motion due to tube-to-seal "stiction". These seals deliver the lowest possible friction coefficient of any of our seals, and are well worth the extra cost!
HINT: the areas in the lower fork tube where the OIL SEAL and the SLIDER BUSHING are located (at the top of the lower fork tubes) should be inspected carefully after dis-assembly and seal/bushing removal for any nicks, gouges, or imperfections. For proper oil seal slider bushing seating and fitment, you want this area to be as perfectly smooth as is possible.
It is recommended that you polish these areas using some 200-, 400-, 600-, and 800-grit FINISHING PAPERS.
ALSO---it's never a bad idea to use some of the 100% Silicone Grease as an "assembly lube" when installing any of these oil seals:
HCP28407 Aftermarket o-ring, oil seal, and gasket installation pure SILICONE GREASE. This small 5-gram (1/6-oz) snap-open "pillow packet" is enough for a few small oil seals, dozens of o-rings, and the like. Each:
$ 4.95
HCP1714 Aftermarket o-ring, oil seal, and gasket installation pure SILICONE GREASE. This generous 14-gram (1/2-oz.) tub goes a long way, because just like Brylcreem, "just a little dab will do ya'!" Each:
$ 9.95
NOTE: the following product(s) can only be shipped via ground transport (which thus eliminates the postal Priority Mail, postal Express Mail, or private carrier Expedited levels of service for this item) and cannot (and will not----don't even ask!) be shipped outside of the continental USA. Additionally, there may be a per-package weight or quantity restriction, and thus multiple-unit orders of this product may have to be shipped in separate packages and will incur additional shipping charges.
HCP20861 Aftermarket industrial-strength SILICONE LUBE, in a large 16-ounce aerosol can. Concentrated silicone sprays on wet, and then dries to a super-slick, clear, non-greasy, non-staining finish. Resists moisture, stops squeeks, prevents binding on all types of surfaces (wood, metal, plastic, rubber, even fabrics). Won't wash away, protect against rust and corrosion, stable from -100 degrees up to 500-F. This fluid is also a great choice for use as installation lubricant for o-rings, oil seals, etc. (similar to our HCP1714 or HCP28407 silicone grease paste) or wherever petroleum-based lubricants are not recommended.
$ 24.95
c) If needed, in addition to all of the above, you can gently heat (heat gun or even a 1500W hair dryer) the area of the fork tube where the seal fits.....this will expand that area a tiny bit, enough to make seal install a bit easier.
d) make sure you drive the seal in with a proper seal driver, or one that is fabricated correctly to push ONLY on the seal.....a proper sized OD flat washer can be a big help in this regard. The seal needs to be driven fully in place so that it "bottoms out" against the flat ledge in the fork tube......otherwise, it will be extremely difficult (if not impossible) to re-install the seal retaining clips.
Although fork seals can be installed without removing the inner chrome fork tube from the lower tubes, the proper procedure is to dis-assemble the forks completely, removing the inner tube from the lower tube. Trying to remove the oil seal from the lower tube while the inner tube is still installed risks damaging the lower tube, since it is very difficult to remove the old oil seals from the lower tube while the chrome upper tube is still in place.
Here is a good video on the entire process:
Oil Seal Retaining Clips:
These C-shaped metal clips retain the lower tube Oil Seals and should be replaced along with the oil seals.
Lower Tube Metal Slider Bushings:
These split-ring bushings press into the lower tube, below the oil seal, and serves as a both a tube guide and absorbs the majority of the side loading of the inner tube as it passes through the lower tube. If the fork oil hasn't been changed regularly, grit and moisture in the oil eventually wear down these slides, which have a teflon-like coating on their inner bearing surface to eliminate resistance.
Lower Fork Tube Oil Drain Screw and Gasket:
These small phillips-head screws, near the bottom of the lower tubes, allows you to drain the tubes prior to doing an oil change, or before tube removal and dis-assembly for seal replacement or other service work. The gasket that goes behind this screw should always be replaced in order to prevent oil leaks.
HINT: this gasket has a very small, very fine recessed area around its inner diameter on one side only..........and that side fits against the bottom of the drain screw. The perfectly flat side of the gasket goes against the fork tube drain port opening. We suggest that all pressure be taken off of the front forks (put the bike on its centerstand, and lift the front wheels off the ground) before you open the drain screw); otherwise, pressurized oil can squirt out at a significant rate and force!
Lower Fork Tube Damper Rod Retaining Bolt and Gasket:
These large socket-head cap screws, on the very bottom of the lower tubes, retains the inner tube damper rods to the lower tubes, and must be removed before the chrome inner tube can be separated from the lower tube for dis-assembly for seal replacement or other service work.
This screw is held in tight!----but it must be removed in order to take the fork upper and lower tubes apart in order to replace the lower tube seals, or any other internal parts.
The gasket that goes under this bolt should always be replaced in order to prevent oil leaks. These bolts, when re-installed, should be treated with a low-strength thread-locking compound.
The HCP4402 Damper Rod Retaining Tool, listed further below in the "Fork Tools" section of parts, is needed on some models to hold the damper rod itself (to prevent it from spinning freely) while this damper rod retaining screw is loosened and removed.
Lower Fork Tube Axle Retaining Hardware:
A variety of fasteners were used to cinch the front axle shaft to the lower fork tubes. Note that models with the front axle in a leading position to the fork tubes only used one retaining bolt (on the right side lower fork tube), while models with the front axle along the lower fork tube centerline (BELOW the fork tubes) used two retaining bolts (one on each lower fork tube).