How to Replace Motorcycle Fork Seals
Fork seals keep the fluid sealed inside the forks, and dirt and other contaminants out. Replacing them takes patience, but it’s a maintenance job that should never be overlooked.
Here are some tips for replacing motorcycle fork seals, as well as a basic breakdown of the steps to replace them.
How to Know if Fork Seals Have Gone Bad
An obvious sign that the fork seals have gone bad is visible fork oil. Dirt sticking to the fork leg also tells you that fork oil has leaked out. You might also see fork oil inside the front fender or on the brake rotor, which can severely hurt braking performance.
On the handling side, a sponginess through the handlebar is also a sign of leaking seals. If you have fork oil on the brakes, you might notice the brakes don’t grab like they’re supposed to. And when the seals on one side start to go, the ones on the other side will soon follow.
Replacing Fork Seals on a Motorcycle
The internals of the fork work close together in very tight tolerances, so even a little dirt can do a lot of damage. Keep your workspace and all parts clean and organized before taking anything apart and putting it all back together.
You’re going to have parts from the triple tree and the forks that look very similar. Pay attention to the orientation of the parts to prevent incorrect installation, and use markers to label parts while you’re working so you can remember which way they go.
Secure the Motorcycle
Motorcycles are heavy, especially larger street and cruiser machines. Make sure you have a way to lift up the motorcycle and hold it while you’re working.
You’re going to be pulling the front end off the motorcycle, so something needs to hold that weight up. Make sure the motorcycle is secured front and back, and side to side to keep it from falling over while you work. Once you’re organized, everything’s clean and the bike is secured, you’re ready to replace the fork seals on your motorcycle.
Every bike is different, but here are the basics of replacing the fork seals on a motorcycle.
Motorcycle Fork Seals Replacement Steps
Step 1. Remove the brake caliper. If your motorcycle has a caliper on both sides of the wheel, remove each one.
Step 2. Loosen the axle and drop the front wheel out.
Step 3. Dig down to the triple tree and remove any plastics or instruments to access the fork tubes.
Step 4. Loosen the caps at the top of the tubes.
NOTE: The triple tree holds the tubes in place while you break the caps loose. They’re a lot harder to get out if you’re just trying to hold them to keep them from turning as you unbolt the caps.
Step 5. Loosen the pinch bolts on the triple tree and drop the fork legs out.
Step 6. Remove the spring in the tube, followed by the fork caps loosened in step 4, then dump out the old oil.
NOTE: You may need a flat-blade screwdriver to carefully pry the seals loose. Pay attention to the order the seals come off and their orientation.
Step 8. Inspect the fork tubes for pitting, which you can fix with polish. Just don’t use anything abrasive, since the goal is to get the tubes as smooth as possible so the seals can protect the tubes properly.
Step 9. Wipe everything down to get rid of contaminants. Use a little brake cleaner to clean up the fork tubes before you disassemble them.
Step 10. Wrap a little electrical tape around the fork tubes to protect them while you’re disassembling everything and guiding the seals back onto the tubes.
Step 11. Replace the seals in the order and orientation that they came off.
Step 12. Refill the tubes with fork oil (refer to the service manual for how much to use). Next, remove the caliper and add just a little more oil to replace the lost volume from removing the caliper.
PRO TIP: Use the depth gauge on a digital caliper, set it just slightly deeper than the manufacturer’s spec, and then fill to that point.
Step 13. Replace the fork caps, and tighten them enough so the fork oil won’t spill out.
Step 14. Reverse the disassembly process to get the fork legs back in place, then replace the plastics and/or instruments, reinstall the brake caliper and wheel and you’re done. After you reinstall the wheel, just make sure the fork tubes are parallel so that the motorcycle tracks properly.