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Burman gearbox mainshaft


Dinny

Well Known and Active Website User
VOC Member
Does anyone know if the prewar and postwar comet mainshafts are the same or the overall length the prewar shafts should be?

Any dimensions will help.

Thanks
Mark
 

Andy B

Well Known and Active Website User
VOC Member
Does anyone know if the prewar and postwar comet mainshafts are the same or the overall length the prewar shafts should be?

Any dimensions will help.

Thanks
Mark
I'm just back from a weekend away Mark, I will get some details shortly when I'm in front of my " still in pieces " gearbox
 

A_HRD

Well Known and Active Website User
VOC Member
Mark,

Sorry, they're close, but they aren't interchangeable. My research suggests:

Pre-war Overall Length: 11.125"
Post-war Overall Length: 11.300"

The main difference is in the large dia (0,9325") longest section with the long splines:

Pre-war: 6.906".
Post-war: 7.125".
(Your items may vary by a few thou).

If it's any consolation, Maughans make both.

Peter B
 

A_HRD

Well Known and Active Website User
VOC Member
Mark,
I meant to mention: Bob Stafford always maintained that you could add a 1/4 thick hardened spacer to the back of the clutch spline shoulder, making the post-war type pretty much the same dimension - and useable in an A single. I've never tried that though...
Peter B
 

vibrac

Well Known and Active Website User
VOC Member
There is a whole family of Burman mainshafts out there once you start thinking Panther or AJS etc
 

Andy B

Well Known and Active Website User
VOC Member
The pre war burman gearbox is identical to the 1935/36 Ariel gearbox, the main shaft is also identical, in 35/36 the Ariels had the Cush rubbers in the clutch same as the A Vincent's. Even in the Burman catalogue, under the part number for the shaft, it states ....as fitted to Vincent and Ariel. I have the original gearbox from my 1936 Meteor and an original Ariel 1936 Red Hunter, same gearbox, shaft and clutch is same except for the duplex on the A. I will post details when I can. I am aware of a complete gearbox that I might be able to get my hands on in the not to distant future
 

Dinny

Well Known and Active Website User
VOC Member
Thanks everyone for the responses. I was checking the clutch alignment yesterday and found th clutch is approx 1/4” too far out. From Peters post I am assuming I have a post war mainshaft as it’s too long. I do have a mainshaft that is 11 1/8” long so I’m hoping that will work, I will see how that looks today.

I’m not sure about putting the spacer on the inside, it would have to be a nice press fit and it it ever moved.....

Good info Andy, I will post how I get on with this and hopefully put the gearbox to bed for now. I did find the clutch parts so I do now have a complete clutch.

Cheers
Mark
 

powella

Website User
VOC Member
I think this is what happens in a Burman box , probably whatever the make , year or model. See photos.
The left shaft has the start of wear on the splines for the clutch basket - all the weight of the bike , rider , fuel etc are transmitted by this 1/8th inch engagement No wonder it wears.
What happens next is that rather than buy a new shaft or weld and file the splines the " bad" bit gets machined off but still retaining the thread I think this is the middle shaft.
The final stage of reclamation is to machine back again and also to shorten and recut the thread.
Also shown is the spacer mentioned by Bob Stafford.
As to the lengths - this is anybody
s guess ! Incidentally there are different threads on the kick start end.The Burman BAP uses the larger 5/8 inch diameter.260492605026051
 

Andy B

Well Known and Active Website User
VOC Member
Sorry for the delay Mark, just back from two weeks up on the Sunshine Coast, pictures of my gearbox mainshaft, this came out of my original gearbox which was fitted and the numbers match the numbers on the build sheet. However who can say it has not been changed during its lifetime?? Overall length is actually 11" 1/8th . I actually have another exactly the same overall length only the splines on the large diameter are shorter as in Peter B reply, Greg Brillus sent me an original gearbox shaft and it was exactly the same as the one out of my gearbox so I am a little confused at the moment about the length of the splines on the large diameter if Peter is correct. Time will tell I suppose when I get my sorry arse in gear. Short answer mate my bike is coming on very very slowly!
 

Attachments

Dinny

Well Known and Active Website User
VOC Member
No worries, thanks for the response. I had a post war shaft but looking though my bits found the correct pre war one and its in, I will find where I wrote down the length and let you know.

Mark
 

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