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Slave Cylinder Plunger Problem (09 KTM 200 XCW)

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I rebuilt the slave cylinder and reverse blead it. Works for for 5-10 clutch lever pulls then looses pressure. So I removed the slave cylinder and the plunger was pushed to far out of slave cylinder allowing fluid to pass the o-ring in turn releasing the pressure of hydraulic clutch. Why would the plunger be moving so far out of slave cylinder???

 

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Edited by BigWeavs

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The piston of the slave moves that far out even when installed ??? That's strange. 

Edited by Doc Brown
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Ran into the same problem  with my 125 sx Check & make sure you don't have 2 gaskets on the slave cylinder. 

It took two rebuilds for my dumb ass to see the problem 

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6 hours ago, Doc Brown said:

The piston of the slave moves that far out even when installed ??? That's strange. 

yep

2 hours ago, Bully D said:

Ran into the same problem  with my 125 sx Check & make sure you don't have 2 gaskets on the slave cylinder. 

It took two rebuilds for my dumb ass to see the problem 

I only have one haha ?

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Take it you've not had the clutch basket etc off. Not sure if the gasket is the problem but you could check KTMs dimension Y to see if you have the correct thickness gasket and also the length of the push rod which should be 178mm. The push rod stops the diaphragm coming out. You'll also have used mineral oil and not brake fluid. Was it a genuine rebuild kit you fitted? Since it should be an interference fit, you can get a slightly oversize o ring which takes up wear (if there is any) in the slave bore, although normally this just prevents fluid leaks. It's a KTM part, though not listed for the slave, just another part of a KTM  engine. We've never had this problem in years of 125 ownership so that's all I can think off at the mo. Bob

Edited by 7Tktm

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10 hours ago, 7Tktm said:

Take it you've not had the clutch basket etc off. Not sure if the gasket is the problem but you could check KTMs dimension Y to see if you have the correct thickness gasket and also the length of the push rod which should be 178mm. The push rod stops the diaphragm coming out. You'll also have used mineral oil and not brake fluid. Was it a genuine rebuild kit you fitted? Since it should be an interference fit, you can get a slightly oversize o ring which takes up wear (if there is any) in the slave bore, although normally this just prevents fluid leaks. It's a KTM part, though not listed for the slave, just another part of a KTM  engine. We've never had this problem in years of 125 ownership so that's all I can think off at the mo. Bob

Thanks. I fully rebuilt bottom end and top end. I'll check the rod length.

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I looked it up. I can't see another part...

But last time I rebuilt mine I remember having to do something over again because I forgot a washer or a small o-ring something in the piston mechanism. 

I think it went behind the piston. But my memory is terrible. 

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I remember. it was a small spring that went being the slave piston. Not sure if that's your problem though.

Maybe it's not flush against the case?

Edited by 2strokezuke

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Ah, you didn't say you'd rebuilt the bottom end. Measure dimension Y, ie end of rod when pushed fully in - It should be no more than 3mm from the slave mating surface on the case. Y dimensions are 2.5 - 2.8 mm use 0.75 gasket, 2.8 - 3.0 mm use 0.50 gasket. 3.0 - 3..3mm use 0.30 gasket. I would say if it is more than 3.0mm you have rebuilt something wrong. Worth a check. Bob.

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Considering what Bob said it could be that there went something wrong with the throwout bearing on the opposite end of the rod that causes that the rod is too far in and the piston travels too far out as it has no counterforce anymore.

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