Diagnosing clutch failure

Hey there - I just had a nice 2-day trip riding in the desert in eastern WA, on my 2008 TE510. First day we spent in the dunes and had a great time, and I didn't notice anything wrong - but when I was getting setup for the 2nd day, I suddenly had no clutch whatsoever - the lever went to the grip with no resistance.

Fortunately, a riding buddy had some mineral oil and a syringe/tubing combo and we were able to bleed the system (the resevoir was totally dry) and refill and everything appeared to work ... though there's some chance that it was getting softer throughout the day. Hard to tell.

What exactly should I be looking for? What could be leaking where? The levels were at 0, so it seems like it's not just air sneaking in somewhere ... but if there is a leak, it's slow or someplace invisible, because I never saw any seepage anywhere.

Any help appreciated!
- Jeff

It sounds to me that the oring in the slave cylinder needs replacing. I think older KTM (99-00) will fit as husky does not sell the part separate.

There's an o-ring on the piston that fails in the clutch slave. Happens just about on every one of those magura setups.

You can get a new piston fom 7602 racing, but if your slave casing is warped like mine was it won't work.

So*...*It*looks*like*my*problems*are*still*here.*

I*got*and*installed the 7602 piston and it went in in what I thought was a proper way - it didn't bind and didn't have any visible slop. I reinstalled everything, filled and bled the system and went for some short pavement test rides and all seemed to be well ...

I'm now camping (and trying to sleep but stressing) at the Desert 100 race outside of Odessa, WA ... And I'm going to have to bow out. I took the bike out for a spin in the flats for about an hour to shakedown a bit more - I had also done some rad repairs - with a lot of heavy clutching, and that too seemed well. I came back from dinner to find that the lever suddenly went to the bar, and sure enough the resevoir was empty again.*

So ... help!

Which of these makes sense as an explanation as to what is happening? And am I missing anything?

- slave cylinder itself: I guess it could be worn out of round ... Though the 7602 piston fit fine
- hose: no visible leaks but I guess it could be hiding. This last failure occurred with very little actual riding, so I guess maybe a failing hose could be getting worse rapidly?
- perch/master resevoir: maybe ... There is a thin seam-like line running the length of the bottom of the inside of the master cylinder resevoir at the perch, but it could be just a casting remnant (and that's what 2 mechanics at one of the suspension booths said). It would explain what appears to be a growing failure, though a crack there in particular seems like it'd just drain into the system
- other??? Seals at the master? Again, no visible leakage up there, though it'd be harder to see ad there IS lube at the lever joint an it could mix with that ...

I'm thinking about ordering a whole new system from Taskys ... I have a weeklong trip to Moab in two weeks, so I can't afford the time to keep dinking. Maybe try fixes in a particular order until it's solved, then return parts not used? But in what order, at this point?

Thanks in advance for y'alls continuing help!

Ps. If I replace the whole slave cylinder, will the Zip Ty Racing slave be compatible with the 7602 piston?

(and sorry about the *'s in my last post ... iPhone going whacky ...

Im no expert with these, and am barley even familiar with them. However, if this was mine, I think id be looking at the slave cylinders o-ring, which should have been replaced with a X ring if you didn't already do that. Any chafing or grooves on that ring and it will not seal properly and leak into the engine.

There was no visible wear at all, actually. Hmm.

I ordered a whole new OEM setup of cylinder and piston, I'll give that a try as well. I need to have lots of options available, as we're leaving in, like, 12 days ...

What is the seal situation up at the master cylinder, in the perch? Surely there are seals up there that could go bad?

Rebuild kits are available for the master cylinder here in the UK and I imagine worldwide from Magura suppliers. *I think* the ones for Huskies are 9.5 mm diameter. The master cylinder type is 163, mineral oil. Hopefully more knowledgeable folks can confirm this.



But I would expect that losing a reservoir's worth of oil out of the master cylinder would leave a pretty obvious mess, so IMHO the first suspect still has to be the slave. Hope you catch it!

There are certainly seals up there and they do go bad. But the difference is that if they go bad, you don't get "mystery clutch fluid loss". You get either "reservoir is full but the clutch mechanism still doesn't work all the time" or "clutch fluid is leaking out of the master cylinder".

Since your fluid is going away with no visible leak, I think you must still have a slave cylinder problem despite the 7602 Racing piston.