Cause of clutch slip

[gleno]

This thread was inspired by the discussion in the Barnett's carbon fibre friction plate thread.

If you experience clutch slip and you have a few years on the bike (but not necessarily a lot of miles) you may want to inspect the slave cylinder.

My clutch had been slipping in top gear at WOT and this was especially evident when the boost kicked in.

I assumed the friction plates were stuffed and thought I may as well redo the system and improve (Evolve) it while I'm at it :clapping:

So I purchased the Barnetts CF friction plates with this in mind.

The cause of the slipping clutch was NOT wear on the original friction plates.

Slip was due to the internal seals on the hydraulically operated piston in the slave cylinder degrading to the point that they had become very soft and swollen. They were so soft that they had began to deposit residue on the cylinder walls.

In combination this restricted the free movement of the piston which could not provide a full release of the clutch plates and was actually moving at an offset angle in the cylinder..

New seals and polishing the inner cylinder restored the clutch to faultless operation.

The Barnett CF friction plates are still in the box but I'll fit them anyway and let the forum know what I think in the product review section.

 

[maleko89]

Yeah, I had the same situation with the slave. Key is to change clutch fluid and not let it "go bad". I change mine once a year. My bike has over 65,000 miles and I changed clutch discs once.

Mark
#1098

 

[shawn kloker]

Yeah, I had the same situation with the slave. Key is to change clutch fluid and not let it "go bad". I change mine once a year. My bike has over 65,000 miles and I changed clutch discs once.

Mark
#1098

Mark,Dot 5 does not go bad,draw water,eat paint or boil under heavy use.

Try it next change.

 

[maleko89]

But it's not compatible with DOT 3/4 so you have to make sur eyou clean the master cylinder and lines really well. I believe 5.1 also works and is compatible with DOT 3 or 4.

Mark
#1098

 

[4gasem]

But it's not compatible with DOT 3/4 so you have to make sur eyou clean the master cylinder and lines really well. I believe 5.1 also works and is compatible with DOT 3 or 4.

Mark
#1098

5.1 is but you're better off with Valvoline's synpower DOT4. Look at the boiling points on them. That's what tells all...:thumbs up:

 

[tim-4878]

I've read that Dot 5 is more compressible than the rest. Anyone using dot 5 notice this? I hate the fact that the dot 4 i use now eats the paint, but i like not having a spongy brake or clutch.

 

[Rusty McNeil]

I don't know if it's true or not but I've heard somewhere that DOT5 is not always compatible with seals and rubber not designed for it; That even if every thing is clean and spotless of the old DOT4 fluid that it may attack seals etc.

I dunno for sure tho'

 

[maleko89]

Rusty, I've heard the same. I've also seen some who didn't change the seals and it worked fine....maybe it just takes time for the seals to fail.

Mark
#1098

 

[one2dmax]

Don't recall which ones but there are synthetics out there that are compatable with regular dot 3-4 fluid. Of course if there's no leak there would be no need to worry on mixing them.

Sean Morley