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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
 

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Moderator
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
 

timetraveller

Well Known and Active Website User
VOC Member
No unexplained noises when I spinn the rear wheel. Would you expect some noise if the sprocket was spinning on the shaft? He was riding it until the clutch cable went and had not noticed anything untowards. However, it is his first bike so he does not have years of experiencing the kind of things we discover on Vins.
 

Chris Launders

Well Known and Active Website User
VOC Member
Racking my brain something reminds me of hearing of a Burman box where whatever retains the final drive bearing failing allowing the final drive gear to move out of engagement. Just something I recall from somewhere.
 

b'knighted

Well Known and Active Website User
VOC Member
On the way to a Kenmore Rally, probably late 70s, I had a problem when the bronze of a selector fork picked up on the steel groove it was running in and flowed around the slot until it was all below the shaft and could drop out.

The replacement fork that I managed to source from a friend of a friend of a total stranger didn’t work for long until it picked up and did the same. I should’ve replaced the sliding gear.
 

shortun

Active Website User
VOC Member
If the cover was taken off it's probably the ratchet type plate that is held by two locating pins on the gear lever mechanism has disengaged or maybe has the mechanism been timed as in the handbook. I put all the mechanism in place removed from the cover then fit the cover then fit the locating bolt last.
 

brian gains

Well Known and Active Website User
VOC Member
decomp' cable can be used as 'get you home' repair, have done so and think it is pointed out in one of 'the books'.
do a search and find my Burman woes,2019?. I went in looking for one issue of no 4th gear drive but found several others.
Slight solace, the Burman can be removed with removal of primary and associated g'box bracketry. Bit of a wrestle but after several remove/replace procedures it becomes quite straightforward, accepting bruises to all parts concerned.
 

Peter Holmes

Well Known and Active Website User
VOC Member
I think what Norman was pointing out was on a twin the two cables, clutch and decompression are essentially identical, not so on the single, the nipple at the clutch actuating lever is different, but from what you say, not withstanding the difference, you made it work, handy tip to know.
 

Martyn Goodwin

Well Known and Active Website User
VOC Member
I would go with Simon on this as I had the same thing happen to my Comet and found that the splines had gone.
I have had EXACTLY that problem, not once, but twice with my Comet. Gearbox drive sprockets had NOT been hardened.

Also can be caused by the drive sprocket nut not being securely tightened allowing it to move ever so slightly then 'worrying' away at the splines on the sprocket. Can even damage the splines on the gearbox output gear shaft.

The give away is that you can kick start the motor, you can change gears but nothing happens at the back wheel - its just like a broken drive chain - till you wake up that the drive chain is intact.
 
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BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
Not directly Vincent related but:
Some years ago, when I had my BMW R75/6 I rode from Oxford back to Leicestershire without being able to use the clutch.
From stationary, this involved paddling in neutral with the engine running and crunching it into gear. Junctions were particularly tricky and required a lot of anticipation to avoid having to actually stop if at all possible.
Having my wife on the pillion didn't make it any easier.:eek:
On my Rapide I have a spare clutch cable taped alongside the one in use. Highly recommended.
 

Bill Thomas

Well Known and Active Website User
VOC Member
If you take the clutch off T.T, There are two big washers each side of the Drum , To hold the rollers together,
One is thicker than the other, I think the thick one is behind the drum, Closest to the gear box ?.
Good Luck, Bill.
 

timetraveller

Well Known and Active Website User
VOC Member
OK Chaps. Thank you very much for the advice. I will now pass all that on to Jason. I have got to the state where I do not want to kneel on the floor to dismantle bikes, I have lifiting work benches, so 'young' Jason will have to do the preliminary work. It looks as though the sequence should be as follow; drain the primary chain case. remove left hand foot rest hanger, remove outer cover, remove clutch paying attention to Bill's advice, remove inner chaincase and then inspect the final drive sprocket and gearbox main shaft. If this is correct then I will send him all the above postings and these instructions. Once again, thank you to all who have responded. Unfortuataley there are no Comet owners locally who I could have approached.
 
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Bill Thomas

Well Known and Active Website User
VOC Member
I know the feeling, I am not good at rolling around on the floor,
But, I think it's a job for an older chap !, With good tools !.
If you take the inner case off, I think the engine will have to be supported,
Hope the gearbox nut is not too tight, But will have to go back tight as Martyn has said,
There are a few tricky bit's to do, I guess we all have to learn, But I think He will need help.
 

Bill Thomas

Well Known and Active Website User
VOC Member
The engine shocker will have to come
Off. I would use a chain wrench to stop the engine turning while undoing the nut.
I put the chain wrench around the body of the shocker.
 

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