Clutch?

[Tom Gaynor]

The plain plates are of three different thicknesses, oh joy. I used only the two thicker ones. I must have put my Burman clutch in a safe place, because I can't find it, but I think it had five friction plates, and needed six plain plates. Or maybe it was four/five. I bought everything I needed (plates, bearings, springs) from VOC Spares. Basically you fill the drum up with alternate friction and plain plates, starting and ending with plain. (Hopefully they are also plane...) The last plain plate should sit just below the top of the drum, so that on full lift (although 20 thou is enough if all the plates are flat) the last one can't escape the slots. Two plain plates together matters nought, because they are both splined to the centre, and act as one extra thick one.
I have no plans to buy a "modern" clutch, there's nothing wrong with a Burman that new plates won't fix. It is basically the same as a BSA clutch - or a Honda, Suzuki, Kawasaki, Ducati...
I have a Burman gearbox booklet (includes clutch details) as a pdf file. Send your email address to sunbeam42@live.co.uk and I'll send you a copy. What you DO need to do is make sure yours is the Vincent version, with 5 springs, and not one of the superficially similar variations with four or even three.

 

[Simon Dinsdale]

I have had clutch slip on my series A Comet since I got it on the road this year after restoration. I kept tightening up the springs , but this made no difference. I then decided to dismantle the clutch, and bingo!!! It had been assembled with two plain plates at the botton of the plate stack. As there was room, I put a friction plate in between the plain plates, checked it wouldn't lift out of the clutch drum and reassembled. I did then have to make a new clutch pushrod as the old one was a friction plate too short, but the clutch now works fine and doesn't slip. When working well and assembled correctly, there is nothing wrong with a burman clutch on a Comet.
As your pushrod appears to be tight even after adjustment, you may not need a new pushrod, just an extra friction plate as the pushrod sounds the correct length for 5 friction plate assembly.
Cheers,
Simon.

 

[Albervin]

The first metal plate in an "A" Comet clutch is extra thick. Maybe the 2 standard plates were used to achieve the same result? You say there was still room in the basket to add an extra friction plate so maybe the friction plates had worn to below optimal thickness. My clutch was very grabby and I ended up cutting new cork inserts (I have way too much time) and now it is sweet as. I agree that a Honda clutch should be a last resort if your basket, sprocket etc. is beyond salvage.

 

[Simon Dinsdale]

Hi Albervin,

Sorry to everybody else if I am going away from the original thread as this is in reference to series A not post war C's.

Yes I was aware that the first plate on an A is extra thick, and mine has that in (120 thou think I think from a cloudy memory). My dad originally built the clutch and reading Paul Richardson's it states there is 4 friction plates in a series A (different for B's and C's) so that is what he put in. The clutch slipped on the kickstart so he thinks he put the extra plain plate in the bottom to increase the spring pressure and new springs from Conways.

The clutch still slipped on the road so I dismantled it. Now knew it wasn't the original off the bike because the original clutch is in a box with a chewed up clutch center and outer basket/drum spreading open from the plates chattering. I compared the original center with the one on the bike and found the new center appeared to be brand new and was longer. ie the distance from the front face to the shoulder where the bottom plate sits was longer by approx 120 to 160 thou. The shoulder was also in a different position been further to the back of the clutch (these figures are from memory, I did not note them down at the time). Both centers were of the 4 spring type. The outer basket/drum also had deeper slots and the new drum had a reinforcing ring the full depth of the drum over its outside to stop the drum spreading open. It was not like the drum the VOC spares now sell where strips are spot welded inside the drum to create plate location which was a later Burman design.

Even with a extra thick first inner steel plate and the rest of the steel plates at 60 thou thick and 5 off post war type ferodo friction plates (not cork) there was still room. I checked everything from clearance between the bottom of the slots in the outer drum and the bottom steel plate to the position of the plates at full lift and all was ok. It all fits in the primary cover and functions beautifully. No drag or slip. No snatch or grab and is no heavier than the V3 clutch in my C twin.

What parts I have I don't know. They are all definitely Burman, look pre war, but measure different to the original in regards to the bottom plate position. My dad got them from his box of spare Burman bits he has aquired over the last 30 years. Could they be Ariel / Panther, I don't know.

Finally the new clutch pushrod required with the above clutch after assembling with 5 friction plates measured at 315mm which I believe is the correct length for a series A, so the extra space found must be in the bottom of the clutch.

Cheers,
Simon.

 

[Pete Appleton]

Simon

Did your replacement clutch basket have the shock absorber rubbers in the back of it like the originals? I would quite like to replace the basket on my 'A' but haven't been able to find any other Burman clutch that uses the same system. I asked the AJS/ Matchless lot over at Kettering and they had never seen one.

Getting really off topic now.

Peter

 

[Albervin]

Simon

Did your replacement clutch basket have the shock absorber rubbers in the back of it like the originals? I would quite like to replace the basket on my 'A' but haven't been able to find any other Burman clutch that uses the same system. I asked the AJS/ Matchless lot over at Kettering and they had never seen one.

Getting really off topic now.

Peter

That is the "Vincent way". I think Burman CP plates will fit but of course, as Peter says, without the shock absorber mechanism you are plating with fire.
Now, where were we?

 

[Simon Dinsdale]

Hi Peter,

Yes all the replacement parts fitted as per the originals including the shock absorber rubbers (Burman pt no. 12X) and pressed metal washers to hold the rubbers. May be worth talking to Draganfly Motors as they provided the replacement shock absorbing rubbers / washers and other Burman parts I required during the rebuild. They stock a lot of Burman parts for pre war Ariels etc which used similar gearboxes and clutches to Series A. The clutch center and outer basket I used did not come from them though.
See:

http://draganfly.co.uk/
http://www.draganfly.co.uk/shop/pi1680705157.htm?categoryId=100

The second link takes you directly to the clutch section. Its not the easiest website to navigate around.
They are in Bungay, near your part of the world Pete.

Cheers
Simon.

 

[rapiderider]

Clutch push rod length

Can anyone tell me what the stock length of the clutch push rod (G96) is?
I used to know this...

Thanks,

Rick