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Clutch Pedal Gets Soft After Motor Heats Up

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So, started to have this issue a little while back while in Idaho where clutch got soft after engine got hot. Figured maybe fluid was just breaking down so drained, bled, and replaced with synthetic fluid. Now, starting to do again even when clutch is not used much during a run. Then goes fine after engine cools off.

New clutch plates? Or someone know of another issue that may be causing this?

Thanks....

Edited by bizness

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Thats a new one on me. I am not a Motorcycle mechanic but have built a few Hayabusa powered sand cars and used stock and Hi-po clutches.

My only thought is that the engine oil is also around the clutch as its a wet clutch it is possible you are not running the right oil and its getting hot and thinning out.

I have always been pretty strict about running Motul 300V 4T 15W50 or Suzuki Performance 10W-40 Oil

I'll be watching this closely..

Edited by fullthrottleguy

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Thats a new one on me. I am not a Motorcycle mechanic but have built a few Hayabusa powered sand cars and used stock and Hi-po clutches.

My only thought is that the engine oil is also around the clutch as its a wet clutch it is possible you are not running the right oil and its getting hot and thinning out.

I have always been pretty strict about running Motul 300V 4T 15W50 or Suzuki Performance 10W-40 Oil

I'll be watching this closely..

Thanks for the input; use Amsoil Full Synthetic 10w50 wet clutch oil (same as what previous owner had used).

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Amsoil Dominator 10w30 is what is recommended on a hayabusa with some engine work. I get that from APE and Carpenter Racing.

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Is the clutch slipping at all? We just ordered a new oem clutch for my buddies king car with HD springs.

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Is the clutch slipping at all? We just ordered a new oem clutch for my buddies king car with HD springs.

No slipping at all; Runs great, but loses pedal after heating up.

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Is the clutch slipping at all? We just ordered a new oem clutch for my buddies king car with HD springs.

No slipping at all; Runs great, but loses pedal after heating up.

Loses pedal.What is that exactly? Is it loss of pedal travel,loss of pedal effort or is it clutch not disengaging or ???????

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Is the clutch slipping at all? We just ordered a new oem clutch for my buddies king car with HD springs.

No slipping at all; Runs great, but loses pedal after heating up.

Loses pedal.What is that exactly? Is it loss of pedal travel,loss of pedal effort or is it clutch not disengaging or ???????

Pedal goes nearly all way down with little to no pressure once it gets hot. Car runs great even when clutch pedal loses pressure; just can't use to start or stop car.

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How close are your lines to the exhaust? Could be boiling the fluid. Only meant to do 400-600* before boiling, depending on fluid.

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How close are your lines to the exhaust? Could be boiling the fluid. Only meant to do 400-600* before boiling, depending on fluid.

X2

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Is the clutch slipping at all? We just ordered a new oem clutch for my buddies king car with HD springs.

No slipping at all; Runs great, but loses pedal after heating up.

Loses pedal.What is that exactly? Is it loss of pedal travel,loss of pedal effort or is it clutch not disengaging or ???????

Pedal goes nearly all way down with little to no pressure once it gets hot. Car runs great even when clutch pedal loses pressure; just can't use to start or stop car.

I don't think it's the clutch itself. I'm thinking it has to be the master or slave. What type of line is run from master to slave and as rock asked,what is the routing? IMO ,pretty unlikely to be boiling but if plastic line it could be heating up,softening and expanding when you push clutch pedal. Edited by fabr

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Is the clutch slipping at all? We just ordered a new oem clutch for my buddies king car with HD springs.

No slipping at all; Runs great, but loses pedal after heating up.

Loses pedal.What is that exactly? Is it loss of pedal travel,loss of pedal effort or is it clutch not disengaging or ???????

Pedal goes nearly all way down with little to no pressure once it gets hot. Car runs great even when clutch pedal loses pressure; just can't use to start or stop car.

I don't think it's the clutch itself. I'm thinking it has to be the master or slave. What type of line is run from master to slave and as rock asked,what is the routing? IMO ,pretty unlikely to be boiling but if plastic line it could be heating up,softening and expanding when you push clutch pedal.

So change out master and/or slave? or is there a way to check to see if that is the issue?

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How close are your lines to the exhaust? Could be boiling the fluid. Only meant to do 400-600* before boiling, depending on fluid.

Great question....will check that for sure next trip out, but I know that it gets close to exhaust before it goes into slave cylinder.

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One thing to check is the outer clutch rod might have "welded" to the inner push rod. If this happens the outer might be spinning and heating up the slave cylinder. Run the car and feel the slave cylinder if its hot when in camp take the countershaft cover off or peak in and see if the rod spins(it should NOT).

If it is lmk and I will tell you how to remove them and replace. Hope this helps...

DPC

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Does the slave cylinder have a sand seal? If it doesnt pulll it off the motor and check it for sand around the piston. My bet is the slave cylinder piston seal is worn from sand causing your clutch problems. You can get a rebuild kit for the slave cylinder for around 20$ on ebay.

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Does the slave cylinder have a sand seal? If it doesnt pulll it off the motor and check it for sand around the piston. My bet is the slave cylinder piston seal is worn from sand causing your clutch problems. You can get a rebuild kit for the slave cylinder for around 20$ on ebay.

Got worse on last trip...going to bring out a new master cylinder and slave cylinder to identify the problem.

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Cover the clutch fluid line (with heat insulation) near the engine exhaust too.

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Maybe water In fluid. When gets hot it vaporizes and acts like it has air in the line.

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