How to Replace a Motorcycle Kickstart Seal

The kickstart shaft seal on a motorcycle loses its flexibility, becomes brittle and starts leaking over time, resulting in the bike dripping oil.  

Replacing a worn kickstart shaft seal is a simple do-it-yourself repair job that can be completed in a handful of minutes. Watch the video above and follow the steps below to learn how to replace the kickstart seal on a Honda motorcycle

Honda CT90 motorcycle kickstart seal replacement

Tools and Parts – Honda CT90 Kickstart Shaft Seal Replacement

  • Ratchet and sockets
  • Flathead screwdriver
  • Hammer

Buy Yamaha race grease

Buy Honda contact-brake cleaner

NOTE: We replaced the kickstart shaft seal on a 1967 Honda CT90, but the process is the same or similar for most motorcycle makes and models. 

Removing a Motorcycle Kickstart Shaft Seal

Step 1. Check for a punch mark on the kickstart shaft next to the split in the kickstart arm, which indicates where the kickstart arm should be positioned. If there isn’t a mark, make one with a marker pen to allow you to position the kickstart arm correctly when you reinstall it.

Honda CT90 kickstart assembly

Step 2. Remove the pinch bolt holding the kickstart arm to the kickstart shaft.

Honda CT90 kickstarter pinch bolt

Step 3. Slide the kickstart arm off the kickstart shaft. If the arm is too tight to move, use a flathead screwdriver or chisel to widen the split in the kickstart arm and loosen it.

Honda CT90 kickstarter removal

Step 4. To remove the old kickstart shaft seal, try one of these methods:

  • Screw a drywall screw into the kickstart shaft seal, then grip the screw with a pair of pliers and pull the seal out from the crankcase.
  • Slide a pick tool around the outer edge of the kickstart shaft seal and gradually pry the seal out from the crankcase.
  • Press a punch tool into the kickstart shaft seal beside the shaft itself and lever the seal out from the crankcase.

Honda CT90 kickstart seal removal

NOTE: Be careful not to drive the screw, pick tool or punch tool too deeply into the seal to avoid scratching the seal housing in the crankcase, which will prevent the new seal from sealing properly.

Installing a Motorcycle Kickstart Shaft Seal

Step 5. Clean the crankcase and kickstart shaft with contact/brake cleaner.

Honda CT90 motorcycle kickstart shaft seal change

Step 6. Lightly grease the kickstart shaft and the inside of the new seal where it contacts the shaft.

Honda CT90 kickstart seal change

Honda CT90 kickstarter oil seal change

Step 7. Press the new kickstart shaft seal into the crankcase. Use a socket with a diameter that’s just under the diameter of the new kickstart shaft seal, and gently tap the new seal into the crankcase.

Motorcycle kickstart oil seal replacement

Motorcycle kickstart seal replacement

Step 8. Reinstall the kickstart arm with the split in the arm aligned with the mark on the kickstart shaft.

Honda motorcycle kickstart seal replacement

Step 9. Make sure the kickstart arm is set at the correct depth on the kickstart shaft so the pinch bolt can slide through the channel in the shaft. Next, reinstall the pinch bolt, then tighten it completely and you’re done.

Honda CT90 motorcycle kickstart oil seal replacement

Ready to change out another seal while you're at it? Watch the video below to see how to replace a shift shaft seal on a Honda CT90 motorcycle