Need some help please guys. Was out today on some hills and bike was fine to start. But as the day went on the bike was reving at the tops of the hills but lacked drive. It got worse and worse as the day went on to the point I had a couple of tumbles as the bike could not make it to the top of the hills. As it’s in all gears I assume it’s the clutch friction plates that have gone? Have taken them out and look to have about 0.5mm on them. Is that worn out or should I be looking at something else . It’s a 2002 315r if that helps and here are some photos. Any advice would be appreciated ?

Sounds more like your lever isn’t returning all the way out and opening the bleed hole into the reservoir. So as the fluid heats up it pressurizes the system and gradually disengages the clutch. 

Also could be debris blocking the bleed hole.

Edited November 3, 20178 yr by dan williams

According to my 315 manual,the clutch plates should be 2.65 minimum,and the springs 35.5 minimum,but what Dan says sounds very likely,seems strange that the clutch got that bad that quickly 

1 hour ago, huski said:

According to my 315 manual,the clutch plates should be 2.65 minimum,and the springs 35.5 minimum,but what Dan says sounds very likely,seems strange that the clutch got that bad that quickly 

Thanks Huski, do the friction plates measure 2.65 front to back or just the pad on one side. my overall thickness is 2.7 across the pad on both faces and 2 in-between the pads?

2 hours ago, dan williams said:

Sounds more like your lever isn’t returning all the way out and opening the bleed hole into the reservoir. So as the fluid heats up it pressurizes the system and gradually disengages the clutch. 

Also could be debris blocking the bleed hole.

Thanks Dan, will check the hole and see if i can get a new plunger kit as i wonder if its just feeling its age. When i pull in the the lever the clutch disengages and engages when i let the clutch go, it just seems to struggle ir i put some load on it. is there a way to see if it is the plunger at the leaver or is it just trial and error ? sorry for all the questions its just a big learning curve for me as i cannot fix it with a hammer ;-)

6 minutes ago, yogibear said:

Thanks Huski, do the friction plates measure 2.65 front to back or just the pad on one side. my overall thickness is 2.7 across the pad on both faces and 2 in-between the pads?

Total thickness of friction plate.

Even a small adjustment problem on the clutch lever can cause the issue described by Dan and still move everything in and out on the clutch stack.  Had the same thing happen on my daughters Beta 80 fixed with added free play in the lever.  

I would double check you have a bit of extra play in the lever and give everything go.  If no luck then like you indicated pull the master apart clean everything up and replace anything if you find it out of sorts.  

Good luck!

Just make sure when you release the lever the piston comes back all the way to rest on the circlip that holds it in the master cylinder. I have crashed and damaged the return spring in the master cylinder but that is unlikely to be your problem as the pressure would force the piston back until it opened the bleed hole. The lever would feel funky but it wouldn’t cause clutch slip.

The only other possibility I can think of is you have some weird oil that gets more slippery when hot but that would be some weird stuff indeed.

Wonder if it's got car synthetic oil in the gearbox,worth changing it if you don't know what's in there

put the clutch back together, new oil and adjusted the clutch lever. on the drive it seemed ok but need to see what happens when it gets warm. This means ill have to go and try again , thanks for the help guys