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Discussion Starter · #1 ·
:mad: I'm having a recurring problem with the clutch/slave cylinder on my S4R. I noticed an increase in free play at the lever at the 600 mile mark but wasn't real concerned because I had planned on having a new 30mm STM slave installed when the first service was performed. After this was done on the ride home (25mi.) I noticed a difference in feel compared to the stock slave and shifting/finding neutral wasn't as easy as I would have liked. I put this down to the fact that the lever span adj. had been changed while at the dealer. I thought that when I returned it to the position I prefer(#3) things would be fine. It really didn't improve that much and less than 100 mi. later I had to take the bike back to the dealer because the free play had increased to the point that I couldn't find neutral. My dealer, who I've known for years, re-bled the clutch and adjusted the plunger that the clutch lever pushes against inside the master cylinder on the handlebar. I took the long way home after the work(50mi.) and the clutch was transformed. Very easy to engage/disengage and shifting was butter smooth. I thought my problems were behind me but after putting an additional 200 mi. on the bike since the last fix the lever free play is increasing again and neutral is starting to become hard to find once more. My dealer was starting to suspect the STM slave before the fix but because I felt an increase in free play before the STM was installed I was thinking that the master cylinder may be bad, as unusual/uncommon as that may be.

Sorry for the "book" but I'm pretty frustrated and thought detail may help. Anybody have similiar problems or more importantly, a solution? I've e-mailed both the STM rep and the company I bought it from but with the Holiday yesterday I haven't heard back from either.

· Premium Member
1,465 Posts
If the slave cylinder is bad, I'd think that you'd find brake fluid underneath the slave and maybe leaking down around your countershaft sprocket. My thinking here is the only way to loose pressure at the slave is to release fluid past the piston seals and out on to your bike and into the atmosphere.

If this was the case, I'd also think that it wouldn't affect your clutch play until enough fluid leaked out that your fluid level got low.

Now, if your master cylinder was going bad, any fliud that pushed past the seals would just end up back in the reservoir, so there wouldn't be much evidence. But again. I'd still think that whatever was wrong would have to be letting air into the system.

I think that if I was troulbleshooting this problem, I'd start by draining the entire system, take it apart and replace the crush washers at the banjo bolts and maybe even the banjos themselves.

I'd then put the ststem back together, but leave the slave off the bike. I'd clamp the slave piston in place with something like a C-clamp to eliminate the clutch springs from the equation.

Next, fill the system and bleed it. When properly bled, the lever should be rock hard as the fluid has no place to go.

If you can't seem to get the system completely bled, look for leaks, or just keep bleeding.

One thing that I've found is that if the banjo on the master cylinder is the highest point on your system, it's possible that an air bubble can get caught there. I usually wrap a towel under the banjo, crack the bolt just a hair, and pump the lever a couple of times. The bubble should get squeezed right out.

Maybe there's something here that can help...

Discussion Starter · #3 ·
Fillmore, thanks for the response. I agree with you about the slave cylinder. To date it hasn't leaked a drop of fluid. The crush washers might be something to explore. I'll have to verify that new ones were installed. I guess that new ones came with the STM slave. I didn't even open up the box.

Here's a really wierd twist to this story. Before I sold my 996 to buy the S4R I had to have the clutch bled. On that bike I had a Evo. slave cylinder. It was on there for close to two years, no problems. I parked the bike for the winter and when I tried to go out for my first ride of the Spring I had very little clutch. After bleeding it was fine. The mechanic said only that he had to bleed a lot of air out of it. Like with the STM, the Evo. unit didn't leak any fluid either. I e-mailed Evoluzione and they had never heard of the problem. They could only suggest that I had really over heated the fluid the last time I rode the 996 which caused condensation and excessive air to build up over the winter. That didn't happen. I didn't ride the 996 hard at all. and with the last ride being in Sept. - Oct. air temp. wouldn't be an issue either. Because of this I chose to go with a different brand of slave for the S4R.

I beginning to think I'm poison to Ducati clutches!!!!!!!!!! ???
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