Clutch slip on kicking over

[Jazzman]

Hi guys,
I bought my C15 a month or so ago, and found that when it came to tdc, kicking it over the clutch would slip.
I fitted new friction plates and springs, having soaked the plated in 20sae oil for several hours.
At first it improved the kicking over a bit but that didn't last, and now it's slipping again.
I have 140 ml of atf in the chain case, and now have the new springs tightened as far as they will go while allowing just enough freedom for the clutch to disengage when required.

At tdc I can stand on the kick start and the compression will hold my full weight for a good 15 to 20 seconds.
If I jump on it the clutch slips.
I keep thinking there's too much compression??
Your thoughts would be appreciated.

Late Addition, I've checked for wet sumping by draining, no problem found.
When it is running, there's no smoke whatsoever even when I throttle it.
Timing is spot on, as is valve clearance etc, oh and clutch cable and push rod are free with slack movement.
Oil is clearly being pumped around evidenced by the return to the oil talk and oil to the rockers.

 
Mike.

[Rupert]

Check there is sufficient clearance between the clutch centre screw and the pushrod. Screw in the centre screw until it touches the end of the pushrod then back it off 1/4 turn before locking the nut.
Expect to re-adjust soon after fitting new plates as they bed in.

[cdsdorset]

Are you doing this with the primary cover on or off?

[Jazzman]

Hi cdsdorset, thanks for the reply. it's with the cover on.

Rupert,
I assumed since there was free play on the clutch lever, there'd be free play on the push rod.
Anyway, I'll do as you suggest and see what happens.

Thank you both for your interest.
Mike.

[Jazzman]

Hi Rupert,
An instant fix!!
I backed off the screw as you suggested, and now I can put my full weight on the kick start and a little jump has it spinning over without clutch slip.
I guess now I ought to be thinking of backing off the new clutch springs.

Anyway thank you for your advice, very much appreciated.

Mike.

[Mike40M]

If not done as Rupert said, the rod and screw can be worn shorter. Had to replace on a newly bought B44 trials bike.

[Rupert]

Pleased its sorted easily. Clearance on the cable at the handlebar lever but no clearance on the pushrod inside the engine probably indicates that the lever inside the engine was resting against the inside of the outer cover. I'd be tempted to back off the clutch centre screw two complete turns to move the lever away from the cover then adjust the cable slack at the handlebar to give correct s clearance in the system.

[Jazzman]

Hi Rupert,
Not such good news.
I went to start the bike today and guess what, the clutch is slipping on kickover again.
I've undone the adjust screw so it's loose and left it like that, tried kicking it, clutch still slips.
The springs and friction plates are brand new, is it possible the smooth plates are at fault?
Other than these plates, I'm at a complete stand still for not knowing what else to try.

Regards,
Mike.
 

[Jazzman]

Further to my last mail, I've now stripped the clutch and found two of the plain plates showing clear signs of bluing, and a third looking so polished I could nigh on see my face reflected in it.
I've ordered a new set of plain plates as a matter of course, so time will tell if this is the end to the slipping saga.

Regards,
Mike.     

[DAVE BRADY]

Hi,

Warped plain plates can cause problems during use but unless they are very bad, should allow the engine to be turned over without slipping.
Put all the plain plates together and hold them between finger and thumb of both hands at 180º and squeeze one side and then the other.  There should be minimal rock and no obvious gaps.  Even new ones may not be perfect.

Dave.

[Jazzman]

Hi Dave,
I'll have a look tomorrow and do the test you describe.
The oil I originally  soaked the new friction plates in was Halfords 20/50 Classic for older vehicles, is it possible it had non friction additives in it?
I'm currently soaking them in ATF which looks considerable thinner than the 20/50.

Mike.     

[DAVE BRADY]

Hi,

I would wash all the oil off the plates and start again.  There is no real reason that I know of for soaking friction plates in oil.  I think this comes from the old cork inserts and not the bonded friction material.
Any engine oil will be non-friction and whilst it can be used in a primary it is best if it does not get on the plates.  The amount that goes in the primary is enough for the chain to run in it as it goes around and splashes to where it needs to be and the rotating clutch tends to fling the oil away from the plates.
ATF is my preferred primary lubrication.

Dave.


Dave.

[Jazzman]

Hi Dave, many thanks for your input on this slipping problem.
I've never owned a British bike before or worked on one, so I'm guided by what I read.
So many times I've read about soaking the plates, which I must add has seemed counter intuitive to me. Now to read you thoughts makes me think I should follow my own common sense in future.

I'll deep clean the friction plates today and rebuild the clutch. I can easily test it with the cover off and let you know the result.


Thanks for your help thus far.
Mike.

[limeyrob]

I've never heard of soaking plates. While we refer to these as "wet" clutches they are not truly wet.  The plates stay reasonably dry as centrifugal force flings the oil off and the primary oil level is set below the plates.  I would be cleaning the plates in petrol or brake cleaner before assembly.

[Jazzman]

Hi Limeyrob,
Believe it or not, I've read whole strings of debate as which oil to soak them in, some saying how you should avoid oil with modern additives.
I've already washed the oil off in watch cleaning fluid (I'm a watchmaker) that strips most oils etc.
I'm also going to go over them carefully with a blow torch, not aggressively so but just enough to burn off any residue.
Ultimately, if I have to, I'll buy a new set and be done with it.

Thanks for your interest.
Mike.