Clutch slip when cold

drikko

drikko

Hero member
Location
Orstralia
I've noticed a few times now that the clutch slips when I first head out for a spin. But it doesn't slip at all when warmed up. Has anyone else heard of this happening?
 
I only ever had it on my old Corsa when giving it the berries when warm.
Sounds like there is a clearance issue when cold, reducing once things warm up and expand.
You could check the bolt tension on the clutch springs or add another washer under each bolt head.

It also only started spinning once it hit about 5000rpm, just as it was getting in it's stride.
 
Mmmm, old plates and springs mate..? Hard to know but won't fix itself... Try new oil, and see how you go. Have all the kit here, except plates, which I reckon we could get from Red's once Maxene returns (soon I think) to pull it down and refit if you need..alignment tool etc...
Have you actually been into the clutch yet, measured things etc. since you got it..? or just been having that wonderful experience of riding a 'real' machine.. ;)
8)
 
Yeah changed the oil today, no difference, went for a great burn over the mountain though, still smiling but sheesh I need those new tyres!  :D :D :D :D

To be honest I'm not sure if I'm imagining it or not, I still don't have the bloody tacho back from Otto  >:( >:(

Haven't looked at the clutch yet, will wait till I'm convinced and hey it's OK once its warm so probably not enough of a reason to go pulling it apart.

 
Drikko,

Although I run the same 20W50 in my GTL as in my RGS and 500, the GTL clutch will slip while pulling hard as long as the engine isn't fully warmed, while the others show no sign of slipping (same circumstances, same road).  I know, shouldn't do that in the first place, but there's a long gradient I need to ascend when leaving home, but it's enough to get the clutch slipping.  Mechanically, everything's fine.  A clutch lightening device is fitted, and I am now quite certain that this might well be the cause.

As long as the oil isn't warmed and still quite thick, the additional friction in the clutch actuation will not let the clutch engage fully or not as quickly as without.

As the RGS doesn't have a cable, things are different, but similar nonetheless.  Behind the slave piston you will find a spring pushing the piston outwards.  I have always questioned it's function.  This spring might act just the same as my GTL clutch cables, preventing the clutch from engaging quickly when cold.  I have omitted this spring in my RGS with otherwise bog-standard clutch, shows no sign of slipping at all.

Not certain if that is a sure-fire fix, but worth a try.

piet
 
While my bike was at Keith's place he told me I had a little clutch slip.
Standard springs were fitted I believe.

I sent up a mixed set of brand new clutch springs to him, 3 normal springs and the other 3 stiff springs - cured!!! (I am a clanky fitter by trade so I have 'wrists of steel').

I got the springs from ebay but I have never seen them advertised again. 'Skyetrader' Andrew Williams from Italian Motorcycle Engineering.
I suppose the old springs 'softened' with age?

However if you are prepared to put your hand a little deeper in your pockets I believe Red has some Kevlar clutch plates. These apparently have superior grip and wear very well.
I'm sure Red will put you in the picture.
 
  Do as Piet suggests and fling the spring, while you are in there give the piston and bore a clean up and fit a new o ring, should fix it.



    Keith
 
sfcpiet said:
Behind the slave piston you will find a spring pushing the piston outwards.  I have always questioned it's function.  This spring might act just the same as my GTL clutch cables, preventing the clutch from engaging quickly when cold.  I have omitted this spring in my RGS with otherwise bog-standard clutch, shows no sign of slipping at all.

Not certain if that is a sure-fire fix, but worth a try.

piet
Click to expand...

The spring for my clutch slave piston on my 120 was obviously lost in the deep and distant past, works fine without!
I suppose the spring helps with clutch actuation to make it lighter? Of course this would pre-load the clutch disengagement so it would be more likely to slip.

On a similar point to Piet, the oil is more viscous when cold so will have a stronger film boundary and thus lubricate the clutch plates nicely so they can slip.
 
I had to replace the clutch o-ring when the bike arrived and there was no spring in there. I suspect the oil being cold theory is a good one. Next time I replace the primary chains I will check it all out.

Cheers

 
Hey you all have me curious about that spring in the slave cylinder now the clutch in my SFC1K slips around 7000RPM and I have changed nearly everything, including new friction plates heavier springs extra plates (maybe it just produces too much power??????)
I will drop that spring out nothing to lose.
M.
 
Think the spring might be fitted to keep a bit of pressure on the bar that sits across the actuating rod, can't see how it could be strong enough to overcome the clutch springs and cause slippage. I would recommend leaving it in place, it was obviously put there for a reason.

Terry
 
My experience has shown it to be a sign of old plates that have got hard and a bit glazed, not necessarily worn down at all. New plates have fixed it.
 
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