mech/susp techs/fork oil change - Houston?
Posted September 27, 2001 - 10:04 AM
Are there any reliable mechanics/suspension techs to do the job in the Houston TX area? What should I expect to pay for this?
Posted September 27, 2001 - 03:17 PM
Posted September 27, 2001 - 03:33 PM
Posted September 27, 2001 - 04:09 PM
If you are going to get your forks revalved goto EBR Performance in Seabrook 281-326-MOTO They are really good and honest people down there. John Mitchell at JM Racing does great work but he is very dishonest (I know a guy who ordered stiffer springs and John put PVC pipe as a preload instead...there is also other stories too but I wont get into it) I would not recommmend JM racing unless you are at the shop and watch everything that they do. Hope this helps,
I get my kicks on a 426!
Motoman393's MX Site
Posted September 27, 2001 - 05:18 PM
From other posts on the list I was under the impression that I needed to completely disassemble the things to do the job properly. I'll stop hesitating, lock the garage and get to work.
I appreciate the recommendations (and cautions) as well.
Posted September 27, 2001 - 08:31 PM
That's funny. I was thinking about doing the same thing. I suppose if I put in the same type of oil it won't matter if I don't get every bit of the old stuff out. That was my biggest concern. Don't know why I'm so worried. I'm a nurse and I always say if you put two drugs in a syringe and they precipitate (make a solid), they're incompatible and don't give it. Don't think the forks are a whole lot different. Just don't want my oils to be incompatible.
Posted September 29, 2001 - 04:32 PM
If you are going to just dump the fluid out and refill, save your money and dont even bother with the job.
Once your clean oil mixes with the sludge in the bottom of the fork, guess what??
A "GOOD" suspension shop will do a complete disassembly and inspection. Ask them if they completely disassemble the base valve and midvalve. Alot of suspension guys dont even know how to get the midvalve in a late model yamaha without ruining the Cylinder Valve.
I agree 80.00 for a dump and fill job is a rip off, but 80.00 for a properly done fluid change as listed below is money well spent!!
Disassemble forks completely:
-Remove fork cap.
-Remove bottoming bump components.
(Note 2001 models have Teflon inserts under fork cap.)
-Taking a 14mm Allen socket (Impact style) and a impact wrench remove the base valve assembly. (Apply downward pressure against the fork rod using a clean towel. This insures that the valve is moves outward as apposed to the valve pushing the fork cylinder out.) Use short bursts and not long durations of RPM as this can damage the components.
-Remove the fork cylinder.
Seal and tube dissembnly:
-Using a subtle blade (Flat but small screw driver) remove the dirt scraper. Don’t pry as it may mar the forks appearance.
-Using a smaller blade remove the circlip that holds the seal in place.
-Heat the seal carrier or the portion of the tube that has a unanodized finish uniformly so as to facilitate easier bushing removal with out damage.
-Using quick but not forceful hits drive the tubes apart. (Speed is more important than force and never yank at the end of the stroke.) Use the quick momentum to drive the tube off. Failure to do as described above often results in bushing damage.
Internal component disassembly:
Fork cylinder: The 3228125 Bumper style fork requires that the stakes at the head of the cartridge be removed before the active and rebound valving can be modified.
-Using a 6mm 2 flute end mill, mill the stakes out of the cartridge. The stakes can be identified as 4 dimples at the head of the cartridge or the CV (Cylinder Valve) (It is best to use an end mill because the CV has very thin walls. A drill with sufficient diameter to remove the whole stake will often pierce the CV walls before the edges of the drill have removed the stake.) Mill to 1.8mm depth. It is very important to keep the edge of the mill just bellow the bottom edge of the stake. Failure to do this will result in the last few sealing threads to be pierced and will cause chronic leakage and hence poor fork performance. Be careful to clean all parts thoroughly of AL chips created by the machining. (The chips like to migrate into the CV exit and plug the valving.)
-Using the light to moderate heat warm the area around the now milled stakes. This is important to relive tension and locking agents used in assembly from the factory.
-Using the CV holder place the components in a vice.
-Using a appropriately sized screw driver or round stock turned to the hole diameter, unthread the cylinder form the CV. Uses a back and forth unthreading technique to help prevent thread galling.
-The nut holding the valving components has been staked from the factory and needs to be ground flat past the edge of the stake to remove the nut and separate the valving and piston. (Prior to the grinding process pack the orifice with grease to prevent grinding chaff from entering and being lodged in the internals.)
-After removing the stake the edge of the nut needs to be radiused of its metal bur that develops during grinding. (This bur may come free during fork use and causes numerous problems.) A polishing wheel such as cratex works very well and leaves an excellent finish. Be very careful to maintain proper shim and piston orientation during removal. Also note that may times small spacer shims are placed under the post spacer, or valve these are easily misplaced and will dramatically impact fork performance.
-Now that all the components are free of the stem radius the first thread to prevent thread wear during reassembly.
-The passive valving (base-valve, or foot valve) needs to removed. The nut can be just turned off on these model forks. After the nut and valving has been removed you will need to radius the first thread in the same manner as the active stem. Proper orientation must be maintained to insure the components are assembled properly.
-Wash and clean all components thoroughly before proceeding any farther.
Assembly of fork tubes.
-Place the axle bracket in a vise and firmly tighten down.
-Placing a bag over the tube lube the seal and install the dirt scraper. (Remember that seals always work with pressure so if orientation becomes unclear use that as your guideline.) Install the circlip, oil seal, backup washer. With round edge toward the seal. Bushing outer and then bushing inner. (After the oil seal is installed remove the plastic bag.)
-Use a 46mm seal driver to drive the seals and bushing into the seal carrier. Install the circlip and then install the dirt scrapper.
Assembly of the Active compression and rebound damping.
-Build the stacks specified and then install them on the stem. By very careful not to misalign any washers or components as they could be permanently damaged by doing so.
Double check all components for proper assembly.
-Tighten the nut down after a small amount of blue loctite has bee placed on the threads. Make sure that the nut is not lose or over tightened, clean all components with compressed air to blow off any extra loctite.
-Put the rod and CV back into the holder and apply a small but uniform amount of blue loctite to the CV threads. (This will serve as both a lubricant and a sealant during reassembly and use.) Tighten the Cylinder down. (Very tight)
Assembly of the Passive compression valving.
-Install the valving components on the base-valve stem add a drop of blue loctite to the threads. Tighten the nut down firmly but do not over or under tighten. If your revalving build the necessary components and stacks.
Installing internal components:
-Place and align the fork cylinder in the tube. Grease the base-valve threads and piston o-rings. Using downward force to the rod place the base-valve in the axle bracket and tighten the valve. Once the threads have been engaged use your impact wrench to finish the job. Tighten in firmly, using quick short bursts. Long and high speed rotations are damaging to the components.
-Place the fork upright and fill with fluid. Let the fork oil settle into the gaps between the tubes by refilling every few moments or until the level stops falling. At this point thread the fork cap on the rod 1 to 2 turns and lift both the outer and inner tube to full ht allowed by the cap. Quickly compress the fork full travel. That should initiate fork bleeding. Refill the tube and bleed the rod by stroking up and down until the action becomes consistent and smooth.
-Set the oil ht by measuring from the fluid level to the edge of the fork tube.
-Double check the jam nut tension on the rod. Do this by firmly holding the rod in your hand and tightening the jam nut down as hard as possible. (Do not ever grasp the rod in anything other than a holder.)
-Extend the rod completely and lay the fork over to a 45 degree angle. Quickly and precisely slide the spring down over the rod. Place the fork cap and bottoming components on the rod.
-Holding the rod with your thumb and index finger tighten the cap down till it seats on the top of the rod. Then insert a thin 17mm and tighten jam nut up to the fork cap. Firmly tighten jam nut to fork cap.
-Bottom fork cap to the tube but do not tighten. The top triple clamp is responsible for keeping the cap on.
Check for improperly placed rods during rebound clicker setting. Compare the depth of screw in fork cap left and right when rebound is full hard. (This is a quick test.)
Reset your clickers and enjoy!
Credit for this indepth procedure must go to Jeremy Wilkey of MX-TECH !!
[This message has been edited by KXVET#207 (edited September 29, 2001).]
[This message has been edited by KXVET#207 (edited September 29, 2001).]
Posted October 01, 2001 - 08:21 AM
that will properly give you correct height.
Posted October 01, 2001 - 01:50 PM
Wow....that's a heck of an oil change.
But I don't think most, if any shops would go to this trouble unless there's a significant mod or failure in the mix. Certainly not for $80.
Just like we don't tear down an engine to do an oil change unless a gear has come apart.
However, your level of detail should be captured for others who want to play with the mid-valve or introduce alternative bottoming systems.
Just curious, where did all this knowledge of yours come from anyways?
Posted October 01, 2001 - 04:07 PM
On a technical note, you mentioned to tighten the nut firmly but not over or under tight. This tells someone the torque is important (which it is VERY important) but gives little in the way of helping them know how far to go. On KYB forks (8mm stud) the proper torque is 48in/lbs. Any more and you stand a very good chance of stripping the aluminum adjuster stud. Once the nut is snug, the check plate MUST move freely against the return spring tension (this also applies to the midvalve/rebound check plate).
Installing the fork bushings alone before installing the seals will help everything to go together easier and with less force. I put seal grease on the putside edges of the seal to help reduce the force required to install the seals.
When it comes time to install the fork spring, one trick Ive found that works well is to stand the fork up on the floor, pull the rod out fully, grab the rod right at the top of the fully compressed fork tube (you should have about 16 inches of rod extended)and drop the spring down until it rests on your fingers. Now take a pair of needle nose pliers and reach between the coils of the spring. Gently grab the rod and now you can *screw* the spring down all the way as you hold the rod fully extended. Now you can install the fork cap/bumper. Fork cap lock nut torque is critical to prevent any damage due to overtightening or loosening.
I prefer to empty the arear between the inner and outer fork tubes before I measure teh oil height. This eliminates the variable of not having the space less than full. Showa forks have a bleed hole to fill this area but the KYB forks do not. Most suspension manuals neglect covering this point (which does alter the oil height).
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