this has me stumped.

my mates bike has a clutch issue and me and a few others have been racking our brains to try and sort it for him.

from cold it slips at high revs but once warmed it'll go up gears without slipping,we thought it sounded like the clutch wasn't fully engaging so we've changed the cable, greased the lever/arm on the cover/rod, adjusted it until there is no freeplay/ lots of freeplay and nothing seems to cure it.

the oil is brand new semi-synthetic motal stuff from gericke and as far as i'm aware it's never slipped before but it's just started recently.

the owner is convinced it needs a clutch but i'm still hoping for it not engaging properly due to ...........something...

a quick bit of history on the bike, it was a track bike for a few years but i said unless it's been doing race type starts ( which he doesn't do ) i don't see how that would wear the clutch.


anybody had anything similar happen, what was the cause and the cure ? or does anyone have an idea of what to check next

It's a strange one.

Have you had the clutch out and measure the springs and plates?

It's odd that it slips less when warm.. I can only think of something being worn and whatever it is is 'expanding' with the heat to take up freeplay.

Probably shooting in the dark :)

it's not it slips less when warm it just doesn't slip. he told me it slipped on the way over to mine yesterday but once warm it didn't let go the whole day no matter how much he " cained the shit outta it " .

i have the same thoughts as you, once warm it takes up the freeplay and engages properly.

it's not been apart to get measured yet but if it does come apart he's doing it to put a new clutch in but i want to tell him it's this fault or that before he gets a clutch and starts it

This is just a theory but... with the oil viscosity decreasing as the oil warms up, any oil between the friction & plain plates will tend to provide more lubrication when cold, as the molecule groups are tighter together, and as such the plates will slip more.. As the oil heats up, molecules more easily squeezed out the clutch plates, and less slip.. This id imagine to be the case with worn friction plates, where there's insufficient path for oil to escape, similar to a tyre tread with water flow.

Definitely check the plain plates for warpage & the friction plates for thickness

could be that the oil was bottled up wrong and is actually fully synth, its a long shot and iv always used fully with no slip issues but could be worth changing out? if it dont work u could always put the old back in when you change the clutch

Well, if you have new oil in there and have replaced the cable, lubed and adjusted everything, then you might just have to get into the clutch proper.

vfrman wrote:Well, if you have new oil in there and have replaced the cable, lubed and adjusted everything, then you might just have to get into the clutch proper.

i'm fearing this.

Probably just a shot in the dark, but have you tried to cable tie the clutch in over night/couple of days might free things up?

I'd go with mexican gringo's theory as the best guess.

If its fine when warm though, I can't see any issue.

"Caining the shit outta it" is ill advised on cold engines, so he's got an incentive not to do so.

That said, clutch replacement sounds imminent, but I personally would be getting my monies worth outta current stock, cos i's tight