A7 clutch (plunger)

[Brian]

Terry,

 I've bought a couple of sets over the years that were not any good. I dont know what brand they were though as they didnt have any sort of brand name on them. The biggest problem with the cheap one seems to be they stick, even if the bike has only been sitting for a couple of days you need to free the clutch up before you start. Another problem is the thickness, the cheapy's are never the correct thickness, either too thick or thin so when you put the clutch together its either like a plate is missing or there are too many. I've been using Surflex for many years now and they are really good, a bike can sit for years and the clutch will not stick. I am yet to wear a set out, the ones in my B33 have done many thousands of miles are are still like new. I havent used them but a friend uses Barnett plates (from the USA I think) and he reckons they are really good too.

It really is worth the effort and expense to get a clutch to work properly, makes a big difference.

Brian.

[olev]

Gday,
After this discussion about a7 clutch plates, I decided to rummage through the basket and see what the star twin has. The plates have composite and metal inserts and look in reasonable condition.....except the gentleman who dismembered this machine some years ago decided to protect the plates by soaking them in oil. I assume the tin cover that screws onto the chainwheel is there to stop oil getting on to these plates. so, can they be saved?? I have seen pictures of a ratbag trying to stamp out a bush fire caused by burning oil off clutch plates. Maybe he should have done a bazza mckenzie.
cheers

[beezalex]

Yes, the plunger clutch is dry.  That is its saving grace and makes it much more effective and eliminates sticking.  I think if you soak your oiled plates in gasoline, they'll be fine.  Also, the rear plain plate is much thicker than the others.  Often, this plate has been replaced by a standard one and you get what Brian mentioned with the thickness funkiness.  I also found a really thin (.030") plain plate in my Flash when I got it....I have no idea where that came from.  With all the correct plates, it workes really well.

[jimbo]

Hello, everyone. I am having a bit of trouble with one of these earlier 6 spring clutches. Under load it is slipping, and make a hell of a lot of noise, metal on metal? Could this be because I haven't tensioned the front sprocket enough? I just did the nut up till I could get the split pin in, then backed it off so it was against the pin.

[muskrat]

G'day jimbo.
The cush nut MUST be done up to 65 ft/lb. There will be a gap between the nut and split pin. If the tensioner isn't done up enough the chain will rattle on it. Tension so the chain has no more than 1/2" deflection on the top run. Does it have the domed cover? Did you use car type oil in the primary?
Cheers

[duTch]

 g'day Jimbo- In addition to what Musko said;

There will be a gap between the nut and split pin.

, I was lucky to find in my treasure chest, a washer that fits in that gap (had to enlarge th' 'ole & run a chamfer on one face to fit the contour of the nut though)...
 It doesn't really do anything other than stop the nut from undoing far if it does break loose, and the spring-nut also holds the main bearing tight on the crank. I expect you'll hear a bit more about this ..

 There is another similar thread from Owain currently running that you may want to listen in on 


 

[muskrat]

I've done the same duTch.
Cheers

[Greybeard]

That split-pin arrangement seems a bit odd. Do you think maybe the original design for locking the shock absorber was different?

[bsa-bill]

That split-pin arrangement seems a bit odd. Do you think maybe the original design for locking the shock absorber was different?

Can't think I've seen one GB, but that pin is a bit feeble up against shock absorber being shocked, although I think maybe when set up right that should not happen?

[Greybeard]

The split pin does nothing until the nut comes undone!

[chaterlea25]

Hi All,
Ignore the split pin, and the dopey lockwasher
Degrease the threads properly and apply some threadlock
There are loads of topics on the forum about the dangers of running the bike with the nut not tightened
and the various tools that can be used to tighten the bastard!!!

If the engine has been run for any distance with the nut loose, check the sump for broken up crankshims

John

[JulianS]

Having cleaned and applied threadlocker to shaft/cush drive nut, screw the cush drive nut on shaft untill it seats on the cush drive sleeve. Then tighten it as much as you can, if you cannot get a torque wrench on the nut torque it consider using a brass drift and hammer.