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WM20 fault diagnosis - cautionary info

Had trouble with the M20 clutch today. I could start the bike easily enough, but couldn't get a gear change without major meshing problems. When re-adjusted to change gear smoothly (or smoothish), there was major clutch slip and no drive (except a crawl).

Spent some time fiddling with the adjusters and scratching my head, then turned my attention to the clutch cable and wasted some more time there.

Finally I took the primary cover off. Removed the inner domed clutch cover. About half a pint of oil gushed out.

This is a legacy of my recent wet sumping problem (apparently now cured - but we'll wait and see). The bike had been laid up for a couple of months. I had oil fill the sump, then seep through the crank bearing and flood the primary case. I did drain the sump, and drained the excess in the primary case, but clearly it was worse than I realised.

I had thought the problem lay in the clutch adjusters. This was because I could start the bike easily enough when I took all the load off the them. I therefore assumed that there was plenty of grip in the clutch and no problem there. Whereas, it's actually a testament to the M20 clutch that it kicked over at all and ran with that much oil inside. The plates were stuck together and dripping.

Anyway, the point is that if you have a similar problem, you know where the trouble probably lies. When you just can't make those adjusters work and give you easy starting and smooth gear changes, look inside the clutch. That's kind of obvious now. But it took a little while to become obvious. The underlying point being that if everything else is okay, the clutch adjusters should be very easy to set. Also, an M20 that kicks over reasonably easily does not necessarily mean a sound clutch.

Anyway, I stripped the clutch, cleaned the plates with petrol (yes, the Health and Safety people will be after me now), and reassembled. Result? Nice smooth clutch with plenty of traction and easy gear changes.

Hope that information helps increase understanding of M20s. Diagnosis, after all, is usually the hardest part.

email (option): dannydefazio@sumpmagazine.com

Re: WM20 fault diagnosis - cautionary info

Hey Danny, I would have thought new plates, or even a Triumph clutch conversion would have been cheaper than a pint of petrol!!!
Cheers, Mick.

email (option): mick@motorbikemike.org.uk

Re: WM20 fault diagnosis - cautionary info

Mick, you honest country folk might still be happy about buying fuel down there in deepest Suffolk, but up here in London we nip out at night with a length of pipe and prefer to nick it.

email (option): dannydefazio@sumpmagazine.com

Re: WM20 fault diagnosis - cautionary info

As an alternative to petrol you can boil the fibre plates in a strong water/detergent mix...this will remove the oil. Leave them in a warm environment until completely dry and then refit.(the environment might be a bit 'warm' if you do it in the kitchen) ...Ian

Re: WM20 fault diagnosis - cautionary info - Note to Ian Wright

Ian, I hope that's a serious tip, because I'll do that next time. I hate handling petrol, even with latex gloves. I assume, however, that using petrol doesn't do any harm to the plates? Would that be correct?

email (option): dannydefazio@sumpmagazine.com

Re: WM20 fault diagnosis - cautionary info - Note to Ian Wright

Petrol shouldn't harm the plates Danny...but yes, that is a serious 'tip'...Ian

Re: WM20 fault diagnosis - cautionary info - Note to Ian Wright

Thanks, Ian.

email (option): dannydefazio@sumpmagazine.com

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