Leaking fork seals - A few questions

Hi All,

I've got a '10 yz450 and I noticed a fair bit of fork leakage on the weekend. I pulled the forks off the bike and did the playing card trick I've heard about on here. It appears to have stopped leaking completely which is great.

My questions are:

  • Does this solution only work for a particularly limited time?

I've got the forks off now and if it's only going to last a couple of rides then I may as well take it to the shop. I did try to do them myself a fair while ago but they only lasted a ride or two before they started leaking again so I'm not too confident I can do the job well enough.

  • I am now concerned that one fork leg has less oil than the other. Can I replace the oil easily?

If I remember correctly these are twin chamber forks? Can I just undo the end cap, empty out the oil and then replace it with the appropriate amount? I've watched a video of a rebuild and the inner chamber was removed and drained independently. Wasn't actually sure if this was required or it was done just because it had to be removed anyway.

Thanks.

Edited by vomitbomb

Well, yes the playing card/film strip/tear-off/business card trick is a temporary fix in a way because the problem comes back the same way it got there in the first place; dirt got past the wipers. Cleaning under the wipers fairly often helps keep this from happening by getting the dirt out before it works under the outer lip of the seal. Use a bit of grease between the wiper and seal to trap the dirt that intrudes so it can be removed more easily.

You can dump the outer chamber oil out through the vent screws or remove the cartridge from the top of the fork, which makes filling a lot more enjoyable. Unscrew the 49mm external octagon (cartridge body/fork cap), not the 32mm internal one. That's the cartridge cover/base valve assembly that opens the cartridge.

It isn't necessary to drain and refill the cartridge unless it needs it for one reason or other. But, if it's never been changed, it probably should be.

Well, yes the playing card/film strip/tear-off/business card trick is a temporary fix in a way because the problem comes back the same way it got there in the first place; dirt got past the wipers. Cleaning under the wipers fairly often helps keep this from happening by getting the dirt out before it works under the outer lip of the seal. Use a bit of grease between the wiper and seal to trap the dirt that intrudes so it can be removed more easily.

You can dump the outer chamber oil out through the vent screws or remove the cartridge from the top of the fork, which makes filling a lot more enjoyable. Unscrew the 49mm external octagon (cartridge body/fork cap), not the 32mm internal one. That's the cartridge cover/base valve assembly that opens the cartridge.

It isn't necessary to drain and refill the cartridge unless it needs it for one reason or other. But, if it's never been changed, it probably should be.

Thanks Gray I'll definitely give the grease a go.

The only reason I wanted to drain and refill both forks was because I'm not sure exactly how much had leaked out & I thought it would now be a pretty uneven spread between the two. Do you think it might be a waste of time?

Also, by vent screw you mean the bleeder screw/valve on the top? I have a syringe I can use to fill the forks up from there but will it drain the outer chamber entirely? The syringe may be the better option for me as I don't have the 49mm tool to undo the end cap.

I actually had the forks done not that long ago. I might have to call the shop to see exactly what oil they would have used.

Thanks again.

Edited by vomitbomb

Also, by vent screw you mean the bleeder screw/valve on the top? I have a syringe I can use to fill the forks up from there but will it drain the outer chamber entirely?

You'll have to invert the fork and pump out the oil, but yes, that will drain most (95% or so) of the oil from the fork.

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