Leaky Forks

[tigmaster]

So, your forks are leaking huh? Ya, everyone suffers from this at one point or another. If you ride your bike then this will happen. You may feel like you need to send your forks out to get this operation done, but in reality you may spend at most 2 hours total. First off, ordering the parts ahead of time is the best practice. So you have determined that the fork seals are leaking, but don’t just buy the seals, also get the dirt seals, those are the seals you can see on your forks. Depending on the age of your suspension you may want to purchase a full front suspension rebuild kit. Pivot Works sells a full kit for $70 on eBay. As a general rule, replace your fork bushings every two to three seasons. You may notice a few differences in the description, but this is intended for the tear-down of Showa and Kayaba forks MX bikes exceeding the 85/150f class. This information will still be useful if you ride a different bike, I just cannot give an accurate description of those forks because I have never worked on them.

So you got your parts now its time to get your forks. Start by removing the front tire. Removal of the tire is done by removing the axle nut then loosing the four bolts that clamp the axle to the forks. You will see what I mean. Slide the axle out and gently jostle the front rotor out of the calipers. Try not to squeeze the front brakes with the rotor out of the calipers. Next is your choice, either remove the brake lever from the bars and keep the brake line and caliper attached to the forks or you can do it the easier way and remove the front caliper by removing the two obvious looking socket cap screws. Then remove the brake line holder that is attached through the triple clamp bolts. RETIGHTEN these bolts for the moment. Next loosen the upper triple clamp bolts making sure to alternate. Now depending on your bar setup you may need to remove them to get to the caps on top of your forks. Or you can just use an open end wrench. The goal is just to loosen the caps while they are still held by the lower triple clamp. Loosen your lower triple clamp bolts now and slide your forks down and out. While pulling down on them twist them back and forth because they can be a pain to get out. Make sure you have also removed the fork guards. Now un-thread the top cap on your forks. It will be thread onto a long rod and a nut may be tightened against the cap. If so use a wrench on the cap and one on the nut to remove the cap from the rod. Next remove the spring retainer and the spring. Note which way the spring went in and which retainer and spring went in each fork. Now in the middle of the rod will be another rod which you can pull out. Note which fork each one came from also. Now turn the fork upside down over a drain pan and pump the inner tube up and down until all fluid is drained. Once all the oil is drained its time to start removing the seals. Take a flat blade screwdriver and place it between the dust seal and the fork tube and pry all the way around the seal until it comes out. Next look inside for a strange looking circlip in the fork. Pry this towards the inside of the fork and up. It will pop up and you can pull it off the fork tube. Now is where you are going to have to trust me. Take the inner fork tube (shinny one) and compress it all the way into the outer fork tube. Now sharply jerk it all the way out. Do this several times until the inner tube pulls out of the outer. There will be a grayish colored bushing on the end of the inner tube. Expand it just enough to remove it and check it for wear. If you see any copper coloring on the outside of it, replace it. Next off is another bushing, check it for wear also. Then comes an aluminum ring. Remember how all these parts came off and which fork they belong to. Next is the oil seal and then the dust seal. Now make sure everything is clean and let’s re-assemble. Take a thin plastic bag and grease the outside of it and slip onto the inner fork tube top. The bag prevents the sharp end of the inner tube from cutting the seals. DO NOT SKIP THIS STEP OR YOUR SEALS WILL LEAK!!! Slip on the dust seal and the oil seal in the proper orientation and use care when slipping them over the bag. Now you cane remove the bag. Slide on the aluminum ring, your bushing, and then slide on the last bushing into the groove at the top of the tube. Slide the tube into the outer fork tube making sure the bushing stays in the groove. The fork should feel smooth if the bushing is in the groove. Slide the next bushing up to the end of the outer tube. Slide the aluminum ring on next and then gently and squarely slide the oil seal into the outer tube. Don’t worry about seating this all the way yet, we are going to use the inner tube as a hammer. Slide the dust seal down against the oil seal and make sure you don’t have the circlip on. Now expand the inner tube, but make sure it does not pull out of the outer tube. Now use it as a hammer until the dust seal is seated against the outer fork tube. There will be a lot of friction while sliding so you may have use a little force. Now carefully pry the dust seal back off and slip the circlip on and seat it one the groove on top of the oil seal. You will feel it slip into place. Now press the dust seal back on. You should be able to do it with your hands, if not use the “fork hammer”. Next insert the aluminum tube back into the tube. My forks take 575 mL of 5W fork oil. Once filled, let them sit for about five minutes. Then pump the inner and outer tube up and down like 20 times and the inner rod up and down and let them sit again for a few minutes. Put the spring and retainer back on and thread the fork cap against the nut with about 20 ft-lbs. Thread the fork cap back into the outer tube and tighten it a little. Put the forks back in the clamps and make sure they are the same height. Tighten the lower triple clamp bolts alternatively until you reach around 15 ft-lbs. Make sure you alternate and do not exceed 15 ft-lbs. Then tighten the fork cap back up to 22 ft-lbs. Then tighten the upper triple clamp bolts to the same torque specs as the lower. Make sure you put the brake line clamp back onto the clamps. Like how I told you after those other steps. Then tighten the caliper back onto the forks. Now put the wheel back on and tighten the axle nut to about 60 ft-lbs. Then tighten the clamp on the nut side to 15 ft-lbs alternating. Then take your bike off your stand and put the front tire against a wall and compress the forks 5-10 times. Then tighten the other clamp to the same torque specs. Everything’s good now and don’t your work about those fork seals for a long time.

Cartridge Forks




Non-Cartridge Forks

[JThompson]

This was a great post. Anyone here have trouble changing there fork seals ?

[wr250f95]

also if its just dripping, at least on usd forks, your forks may not be done. take a small strip of negative flim and run up through the area where the cartridge enters. this may fix it, if it dosnt your seals are blown.

[tigmaster]

u stole that from twmx. lol, at least give them some cred.

[wr250f95]

um no i didnt, I learned it form my neighbor who may have gotten it off of twmx.

[tigmaster]

ya twmx posted a tuesday tip on it.

[tigmaster]

Bumpity Bump.

[JThompson]

Thank you tig