B52 Clutch

iandusud · Post by **iandusud** » Fri Dec 17, 2010 12:50 pm

Hi folks. I've just reassembled the clutch on a '56 Model 20. It was missing two plates, one of each, which I have now fitted, however the stack seems a bit high to me, as the outer friction plate only just engages with the drum. Is this normal? Any suggestions as to what might be amiss?

Thanks, Ian

Groily · Post by **Groily** » Fri Dec 17, 2010 2:06 pm

Can be quite tight Ian, especially with pattern friction plates which might be a tad thicker than the originals? Are you saying the outer plate only just engages with the clutch in - or with it disengaged?
If the plate(s) can't come off either drum or centre when the clutch is disengaged, it's probably OK and with time/wear you'll get a bit more engagement.
If it was seriously too fat, you'd probably be having trouble with the push-rod and its adjuster (seemingly too short), or the angle of the lever at the kickstart end - where the lever/captive balls would likely make a characteristic loud click as they were asked to move too far within their discs as you pulled the lever in at the bars.

If it engages and disengages smoothly with everything else looking comfortable and no drag or slip, I'd stick with it.

But if a plate falls off when you disengage the clutch, then you need to look again.
If you have one of the thicker plain plates as the first one on against the drum . . . sometimes swapping that for a standard one can get you a small gain. Or reversing it might as, if memory serves, the splines are offset.
Hopefully the clutch drum and centre etc are correctly mounted - ie not spaced out relative to each other by any non-standard bit for some odd reason?
If as and when it's right, it'll be a beauty - smooth, light and a real pleasure.

iandusud · Post by **iandusud** » Fri Dec 17, 2010 6:12 pm

Thanks for the answer Groily. I haven't yet tried disengaging the clutch because I'm awaiting some parts. I'll try as you say and see what happens.

Cheers, Ian

alanjennings · Post by **alanjennings** » Fri Dec 17, 2010 6:29 pm

Pattern parts are a b----r! My mate spent weeks getting his Norton clutch to work properly after fitting all new plates-they are too thick! He tried leaving one out-no good, had to sand some down to get it to work.

iandusud · Post by **iandusud** » Fri Dec 17, 2010 8:10 pm

The replacement plates came from Jampot Spares and the friction plate is definitely thicker than the one's already there, but I don't know how worn they are.

Ian

RogerNorman · Post by **RogerNorman** » Sat Dec 18, 2010 3:31 pm

You need to get the thinner drive plates if thats the case. The 'Modern' bonded plates are thicker than the old cork plates and correspondingly need thinner steel plates.
Presume you haven't got a 350 clutch on a 500. The extra plates don't fit in the smaller drum. Apart from the lack of adjustment the usual give away is that you pull in the clutch and the last plate falls off the end of the drum!

iandusud · Post by **iandusud** » Sat Dec 18, 2010 3:48 pm

Thanks Roger. Can anyone tell me the dimensions (ie depth) of the two clutch drums?

Ian

rex.webb · Post by **rex.webb** » Sat Dec 18, 2010 9:11 pm

Surley when the,s new "THICKER" clutch plates are supplied a not should be included ?.
How is one to know if they are as the originals ? or thicker ?. Hope all goes well with this clutch as the WARMER weather will soon be here???.
Well "I CAN LIVE IN HOPE".
Ride With Care and Live Long

laxy · Post by **laxy** » Sat Dec 18, 2010 9:56 pm

its the same with new pistons from the club Rex. No note to tell you they need twice the clearance of the original.Dont ask me how I know this

Groily · Post by **Groily** » Sun Dec 19, 2010 10:16 am

Hi Ian - some measurements of two clutches which have seen service over the years on one of my twins. Sorry, don't have a 350 one (or don't think I have unless someone says 'Oh yes you have mate!') so can't make a comparison

Here goes:

Clutch drums, 2 off, identical - depth inside from sprocket face to front edge, 1.47" give or take.
Clutch centres, also 2 off, identical, depth from 'stop' on rear of spline to front face, 34.5mm or 1.36". More important.
Plate thickness:
plain plates - all mine are between 66 and 68 thou
used friction plates, 3 types in the pile - all have metal thickness of 95-100 thou. An original style used-but-OK plate with inserted segments has a total thickness of 195 thou. Some very knackered bonded ones show 160 thou, while a spare set of perfectly good ones, show 195 thou again. No idea of makers, but bound to be from JSL or AMC Classic Spares (or maybe some from Hamrax or Russells a million years ago). So maybe these ones were all made to spec?

Looking at http://archives.jampot.dk/Technical/Tra ... d_view.pdf ('cos I can't remember how many plates there are and am not about to take a bike apart in the snow!), it looks as if - assuming the pic is good for a twin and isn't a '350'!) there are 5 driven plain plates and 4 friction plates.

The total thickness of those 9 plates, starting and finishing with a plain, would be 1.115" completely dry and clean. Which would leave plenty of spline on the centre for clutch lift and a safety margin. With some oil around things (and heat), the clutch will be a bit thicker obviously, but still safe as houses.
There should be no question of running out of space for friction plates on the outer drum with its greater depth, given the fact the outermost plate is plain.
Be interested to hear what you've got! Good luck anyway.