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G: Gearbox Burman Gearbox advice needed.

timetraveller

Well Known and Active Website User
VOC Member
The late Nick Wingrove's son, Jason, is now riding his father's Comet. He phoned me Suday evening to say that he had broken down about a couple of mile from me and could I help. I went out to find him and the lower nipple had pulled off the clutch cable. He has now bought and fitted a new cable but there is a further problem. There is no drive. I have just been over to see if I can help and I find myself out of my depth. The primary drive seems to be correct and I can kick the engine over on the kick starter, which to me indicates that the clutch is holding. The rear chain is intact as are the rear brake drums, sprocket etc. To start with the clutch cable was incorrectly adjusted as there was no free play but I sorted that out. I have tried moving the rear wheel by hand while Jason changed gear and at no point is there any sign of any of the gears trying to engage. The kick start cover was taken off and the pinion which is rotated by the gear change lever was moved with the aid of a set of pliers and it is just the same in that spinning the rear wheel never engages any gears no matter how the gear change shaft is rotated. I am not familiar with the Burman gear box so if anyone has any advice or can think of something else to check that will avoid taking the bike apart to remove the gearbox then that would be very helpful. Thank you in advance
 

Piston Pete

Well Known and Active Website User
VOC Member
I have heard of some Burman final drive sprockets being made of the wrong material in the past and so stripping their spline in the final drive sprocket itself . End result is it just spins on the output shaft which would give the results you are seeing.
Just a thought.
Simon
This has happened to me twice with my Comet - the splines on the sprocket wore clean off with the result that the engine runs , but no drive. First time was 100miles north of home , 2nd time 100miles south of home ! The only giveaway was the "chattering" felt through the clutch lever , this was the wear in the splines .
 

timetraveller

Well Known and Active Website User
VOC Member
On the bike I am helping with the splines had worn away so completely that even turning the rear wheel over to move the chain over the sprocket did not produce any noise of feeling of roughness. The remarkable thing to me is that there was no sign of this untill the clutch cable broke. I am guessing the the sprocket was held just enough by the pressure of the large nut to prevent it being loose. My post #40 above has an error in it. Because of my lack of familiarity with the bits I wrote that the splines which took the final drive sprocket showed signs of wear. That was wrong. It was the splines which hold the clutch centre, which seems to only go onto the splines by about 4 mm. Hard to criticise something which has lasted seventy years but it does look as though a longer overlap of the splines would have been better.
 

vibrac

Well Known and Active Website User
VOC Member
If you need new sprockets for the comet its a chance to go for 5/8" X 1/4" rear chain ,also the honda clutch has shock absorbens so just the job if fitting an electric start
 

Martyn Goodwin

Well Known and Active Website User
VOC Member
If you need new sprockets for the comet its a chance to go for 5/8" X 1/4" rear chain ,also the honda clutch has shock absorbens so just the job if fitting an electric start
There are articles in the OVR archives on fitting a Conways Honda Clutch to a Comet (Conway supplied instructions are incomplete) and also on the gearbox drive sprocket wear and replacement
 

CoreyL

Well Known and Active Website User
VOC Member
There are articles in the OVR archives on fitting a Conways Honda Clutch to a Comet (Conway supplied instructions are incomplete) and also on the gearbox drive sprocket wear and replacement
Is there a way to search the archives, Martyn? Or can you direct me to the OVR issues that address the Honda clutch installation on a Comet? Thanks!
 

Martyn Goodwin

Well Known and Active Website User
VOC Member
On the OVR web site there is a contents document in PDF format. If you open it you can then use the search facility in the pdf reader to search for any key word you like.

I just did that and the information on the Conway / Honda clutch is in edition 32
 

vibrac

Well Known and Active Website User
VOC Member
I would have thought that by now the Honda clutch donor bike (I do have the bike details somewhere) is getting as rare as a white Shadow (Certainly "we are waiting for another clutch to become available" is not an unknown plea). So is there another more modern donor machine whose clutches are even now filling the scrap yards?
 

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