clutch rattle/chatter

My 1974 MK2a commando has developed a loud and very irritating clutch rattle which starts when the plates first separate and gets worse the further they separate.This noise is particularly noticeable when the bike is at a standstill with the clutch lever pulled right in to the handlebar.
The gearbox was rebuilt 4K miles ago with new bearings,seals etc and all worn internal parts replaced.
The clutch was rebuilt at the same time with all new parts and has four surflex plates fitted and four steel with a thick alloy pressure plate (all from Norvil). The gearbox mainshaft is not bent and the clutch is running true.
I have checked the clutch alignment with the primary chain off and it is correctly aligned. I have checked all of the clutch plates on a surface plate and none of them are bent. The clutch centre nut is torqued up to 40ft/lb and retained with a tab washer.
I have checked and double checked all of the clutch components and settings and everything seems ok and the clutch works well it just makes a lot of noise.
I have contacted Norvil and the NOC and we are all scratching our heads over this one.
Either I have made a very basic error somewhere or this is rare fault which hopefully one of you can sort out for me !!
Any help would be much appreciated.

Regards

AndyKingg

Bent pushrod? Worn actuation ball? Basket back plate rivets lose? Basket bearing goosed?
Just a few.
Cash

Thanks

I will check these out and let you know how I get on.

AndyKingg

Since you don't have a belt drive the noise is more unusual but with very little (None) oil on the plates they will be free to jingle in the drum. Do you run a very low primary oil level? Just a thought. I have a belt drive and it sounds like a Duke's dry clutch with lever pulled in.

I would check the clutch drum and clutch center for any noticeable amount of side to side wear from the plates and steels.

What was in there before you changed over to the surflex plates? Were any steels changed out? Just thinking about the stack height...

What type of Surflex plates do you have, steel based or aluminum? Many have had problems with the Surflex aluminum plates. I have always used Surflex steel based plates with no problem. As can be seen in the attached link, the aluminum plates wear the splines severely. This could be your rattle.

Ron's right about the alum. based plates. In use little pieces of friction material will flick off each one of the inter teeth these bits pack up inside the clutch pack.
What I have done is use a damaged extra thick pressure plate that people like to sell. What you do is chuck it up in the lathe and turn off the thickness of a steel plate. And than use a steel plate up against it. It will never be damaged again and the extra stock on the pressure plate can be used to get the stack height just right.

Thanks for the feedback everybody.

I have rechecked the clutch basket, centre, and all the plates.
There is only very slight wear on all of these components.
I have checked the pushrod and the actuating ball and these are ok.
The clutch has 4 aluminium surflex plates and 4 steel with a thick dural pressure plate.
Norvil recommend that you put a steel plate in first and a surflex in last.
With all these plates in there is only just enough room to fit the diaphragm spring and circlip so I am assuming that this set up gives you the optimum stack height ?
I rechecked for play in the clutch centre bearing with all the plates out and this time I found some but there is also some flex in the mainshaft - is this normal?
I will replace the clutch centre bearing as suggested - is this a standard bearing or is it a special ? ( I am not familiar with the dot system mentioned in the works manual).

Regards

Andy Kingg

andykingg said:

I will replace the clutch centre bearing as suggested - is this a standard bearing or is it a special ? ( I am not familiar with the dot system mentioned in the works manual).

Click to expand...

It is supposed to be special bearing.

Here's a previous thread about the clutch bearing that could help?: Http://accessnorton.com/norton_commando1629.html

Thanks for the bearing information links.
I entered the bearing dimensions from the factory workshop manual into a
bearing search engine and the bearing I need is a 6007C2 deep groove ball made by NTN.
We deal with NTN at work so I should be able to get some free of charge.
Many thanks for your help.
Send me your postal address and I will post a couple off to you as a thank you.

Regards

AKG

andykingg, Norvil sells parts,... your thick dural pressure plate doesn't stand a chance against a friction plate you will see this later. And if you have run those alum. core plates for any miles and not had flaking well your a gentle rider indeed. The main shaft moving is bad Ju Ju Read high speed bushings a whole other thread. Can I have some clutch bearings please?

Norbsa

I thought about what you said and I will not run the pressure plate up against the friction plate.
I am a sedate rider hence the low level of clutch wear - in my experience if you thrash old british bikes hard, however well maintained they are they blow up. I have an old kawasaki that I use for thrashing.

I managed to get 4 bearings from my supplier (2 for me and 2 up for grabs) these are 6007C2 2RS

I can let you have one of these bearings and the moderator can have one too. Just Email me a postal address - my Email address is akingg1960@btinternet.com.

Thanks again

andykingg

andykingg said:

and the moderator can have one too.

Click to expand...

Thanks very much for your kind offer Andy, but I'd rather it went to somebody who may be in greater immediate need of it than I am myself; -as it is likely to sit on my spares shelf for years, and I wouldn't really want to receive preferential treatment, -just for being moderator.