Clutch...

C

cwis

Full member
Hello huge Laverda brains!

Adjust clutch when cold, and when it warms up it drags - can't get neutral.

Adjust clutch when hot, and when cold the cable in constantly under tension (and the clutch bits wear!).

This behavior is the same if I use the standard clutch actuation lver, or the longer one I got from Lav mania many years ago.

So - is this expected behavior? If so - fine. I'll adjust my clutch on the move when the lever starts flapping about when the cable suddenly goes slack.

If not, why is it doing it? Yes - I know, expansion and heat, but WHY? If I do a hard take off from stationary, the clutch sometimes makes a squawking noise as it takes up the drive (when hot). I'm not sure whether this has anything to do with it?

I had the clutch out years ago, and it looked fine - no warped plates, plenty of wear on the fibre plates, etc. I've only done a couple of K since.

Best of regards,

Chris
 
Chris, I've got the same symptoms on my 3CL. I'm using the long release arm I got from Wolfgang  and it works fine until it gets hot.I've tried making some longer pushrod sections to maximize the lever travel/leverage but to no avail. I'm wondering if the clutch fiber plates are too old and the material is expanding from too long in oil or maybe hanging up on the hub/basket from expansion. Anyone have any ideas?
 
My '73 3c was just the same, and I got it with less than 3000km on the clock. And there was no such thing as an "easy clutch lever" in those days, we were real men back then (with sore wrists). But the cable would get slack in traffic with frequent clutch use, then tighten up again when the oil cooled, exactly as described. I just got used to adjusting it while riding.
And my '78 Jota does exactly the same thing. Although I do have a wimpy clutch lever installed, guess I'm not a real man anymore :D

Ken
 
Make sure you case harden any clutch push rods,my first attempt years ago was using Silver Steel,and it lasted about 45minutes,suprised me how soft it was.
 
The steel pushrods won?t expand and contract enough to cause this, will just wear and stay there.
It can really only be the fibre discs expanding, increasing the distance to the pressure plate. My racebike does this, the clutch is a bit slacker when I get back to the pits, but it still is free enough to snick neutral at a standstill.
Maybe it is your riding style slipping more clutch than normal, not selecting neutral for even brief stops? Just conjecture.
Perhaps the new kevlar plates are more resistant to this, any reports?
(Keith has my new kevlar ones in his bike to run them in for me!!??? :D)
 
I reckon it's squishy clutch friction plates too. I have some of Red's kevlar plates in my Jota, as does my brother in his 3C. No problem at all with either bike. There is plenty of travel in the lever to go from fully engaged to fully disengaged regardless of engine temperature. No slipping either. I haven't adjusted the clutch cable on mine since the day I put the kevlar plates in.

Cheers,
Cam
 
Interesting, during racing at the fuel stops we always take up the slack but next morning its as tight as a drum and will slip.dont happen on my road bike but then iam not pushing the bike as hard as Fred and Max :-\ :-\ :-\ :-\ :-\ :-\ :-\
 
3C_Stefan said:
From engine dead cold 15?C to pretty hot 100?C there has to be expected a difference of about 1 to 2 mm in cable slack due to thermal expansion of the engine casings
Click to expand...

Hi Stefan

Good point Stefan. But I think 1 to 2mm is a bit of an over-estimate, so I just did a quick calculation. The difference in expansion between engine casings and clutch pushrod mechanism is about 0.16mm over that temperature range (15-100?C). That's about one sixth of a millimeter. I guess the normal length clutch lever arm would multiply that by about 2 at the cable, but that's still only a fraction of a millimeter, which would be barely noticeable in clutch cable adjustment. Perhaps with the long lever arm it might come to around half a millimeter - maybe half a turn on the cable adjuster.

Cheers,
Cam
 
No battle Stefan  :D

No order of magnitude difference either, just an accumulation of errors.

I didn't measure the length of the clutch pushrod assembly, just guessed 200mm. Also didn't know 60/17 lever ratio, so I guessed 2:1. I also used Coefficient of expansion of 22 for Al and 13 for steel, so all my paramaters were tending towards a lower result in my calcs than yours. The most significant being the lever ratio. I concede that your measured data is better than my guesses.  ::)

Anyway, using your numbers I get the same 0.9mm at the cable as you. But that's probably still less than 1 turn on the adjuster.

I don't think expansion of the clutch basket would make much difference as the basket itself doesn't affect the operating range of the clutch mechanism. Thermal expansion of the fiction material in the stack of plates would have an effect. But I'm not sure what that stuff does when it gets hot because I don't know what the binder in the friction material is. Some polymers have a very high expansion coefficient so it could be quite significant.

Cheers,
Cam
 
Cheers for all the replies all!

I estimate I get about 3mm of slack appearing at the handlebar end of the cable when the engine is hot. It's disguised slightly by the vibes over 4K loosening the cable adjuster on the clutch - need to stuff a wave washer or something in there, or I can ride along looking at the barrel of the adjuster spinning happily....

Interested to hear from anyone with a similar issue that has replaced the clutch plates!

Chris
 
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