Upside-Down Fork Seal Replacement

If you see oil leaking from your forks, or if it's been more than a couple of years (according to the manual), you might need to replace your fork seals. It's a bit of work, but definitely with the reach of garage mechanics. This article is geared specifically to the "upside-down" forks found on the Vulcans and other motorcycles, but applies also to regular forks. Before you start down this road you might want to look at SealMate Fork Seal Cleaner. You might not need to replace your seals if there's just a bit of debris in there.

The first step is to head over to YouTube and watch Delboy's video. This is a clear, well-presented video showing the entire process once the forks have been removed from the motorcycle. I'm not going to rehash the entire process here.

Next, get together the parts and specialty tools that you'll need. You can generally mock somehing together from other tools or materials, but with the money you'll save by doing the job yourself you can include the right tools.

  • All-Balls, Boss Bearings and others make seals and dust covers that you can find on Amazon. Be sure to get the right ones for your model; if you want OEM parts is a great source.
  • Red rubber grease. You don't need much, so if you find a smaller quantity (that's cheaper), go for it.

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    Seal driver. With some scrap pipe you could make one, but for the price it's not really worth the risk of scratching the inner fork tube. Delboy shows one like this on the left

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    However, for the Mean Streak, the outer tube seems to be a bit deeper than most, enough that the adjustable driver wasn't deep enough to push the bushing back in. It's not hard to push in (though it could be) and probably could have been done along with the seal, but I didn't want to risk damage to the seal in the process. So, I got a Motion Pro "Ringer" driver to do the job. These aren't adjustable, so get the right one for your forks (43mm for mine).
  • There's also one "specialty" tool that will make your life easier, though people have worked up alternatives with a piece of pipe and a grinder. This is basically an extra-long socket with prongs to fit the castle nut that's in the left fork, Kawasaki part number 57001-1502. If you choose to buy one, it's around $100 or so, so this makes the operation a bit more expensive. If you can borrow or rent one from the local shop, so much the better. If you think you might use it again (got multiple bikes?) then it's probably worth the purchase.
  • Other basic tools you'll need:
    • Small screwdriver
    • Long-nose pliers or vice-grips (helpful to hold up the piston when reassembling the right fork)
    • 14mm and 17mm open-end wrenches
    • 24mm socket to remove the fork caps
    • Plastic milk jug or similar to make the seal-protector (see the video).


Tips that I've Learned

  • Loosen the fork caps while the forks are still clamped in the bike.
  • The left-fork castle nut isn't very tight. You can loosen it while the fork is still attached to the bike but remember, once the cap is removed things can get messy.

Now that you have everything go watch Delboy's video again, and one more time for good measure, and get to it.

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