Grabby clutch, S4R

[The Clockie]

This is a better place to put this enquiry, rather than the Random Chat heading.

My new-to-me S4R has a grabby clutch for no obvious reason, since the plates all look OK. Possibly it doesn't have the belleville plate in it: I didn't check. Has anyone experienced this and cured it? I could just buy a new Barnett clutch pack, the best I've experienced, or even try doping the plates with lithium grease as I've seen suggested elsewhere, but that must cause clutch slip, surely?

Nick

[slob]

I assume it all looked okay when you stripped it?
Did you measure the stack height?
Did it have a dished plate near the bottom of the stack?
Take one of your extra friction plates out and see what it feels like?

[Darren69]

Assuming its the original clutch, what's the mileage? They do wear and its usually the basket or the friction plates that are the problem.

[The Clockie]

Problem fixed; the S4R now has a nice smooth clutch engagement just like my ST4!

I changed the friction plates for an old set bought from Dr Desmo in the US many years ago. Perhaps more significant, there wasn't a belleville or dished plate in the stack when I got the bike so I made my own. Ducati belleville plates are a very shallow cone shape, but Barnett ones have a wave profile which I could quite easily replicate just by whacking a thin steel clutch plate in four positions equally around the circumference. The bent bits need to be little more than 10 thou off flat to give it a bit of springiness relative to the other flat plates and ease engagement. Hopefully the sweet action will last, while the clutch is nicely silenced and the tabs protected from further wear by the two friction plates dropped into the basket before the rest go in.

So far as I can see, the actual stack height is not critical so long as plates can't come loose when the clutch is disengaged, and the pressure plate contacts the loose plates before it bottoms on the splines when engaged. I simply mix and match to get the pack to that situation.

I had a great ride after doing this, made a deal more comfortable by reducing preload and compression damping at both ends. The ergonomics of the S4R suit me well, particularly when there is sufficient wind pressure to unload my wrists: a slow pottering bike the S4R isn't!. The speedo under-reads compared with roadside radar which seems unusual. Just as well the tyres are nearly new and not low on diameter else I'd be getting into trouble without realising it come new rubber time!

Nick

[350TSS]

With new tyres it is more likely to "under read" as the circumference is larger, the speedo counts the wheel revolutions so you will be going faster with new tyres for the same wheel turn count,

[The Clockie]

With new tyres it is more likely to "under read" as the circumference is larger, the speedo counts the wheel revolutions so you will be going faster with new tyres for the same wheel turn count,

Exactly my point! Until the rear tyre wears down, I'll always be under-reading the speed so my enthusiastic blasts now are even faster than the speedo shows, and all achieved on the fat of the mid-range without going near double digits on the taco. Pretty impressive beast!