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Burman Gearbox Leak

Martyn Goodwin

Well Known and Active Forum Website User
VOC Member
I continue on my journey to restore my Comet to (hopefully) pristine condition.

Some while back I rebuilt the Burman gearbox, replacing all the bearing, bushes and all of the spring box components. I am running it with Penrite Semi-Liquid grease but am plagued with a oil (or should that be grease) leak from around the gear-change lever shaft. After every run there is a generous smudge of grease on the gearbox cover with some making its way onto - and thus staining - the exhaust.

I now am in the habit of carrying an old rag and every time I stop its a quick wipe of the gearbox cover to try keeping the grease under control.

For what its worth I have installed a felt washer (home made) between the gearbox case and the gear change lever [as I have also done with the kick start lever]. Also I have put a 1/16" vent hole in the gearbox cover cap - the bit that goes over the clutch lever - in an attempt to relieve any internal pressure - but all to no avail; however there are no leaks from around the kick starter or from the new breather hole.

Question - is my experience common? And - what can be done to try to eliminate the grease weep from the gear change shaft?

Martyn
 

Black Flash

Well Known and Active Forum Website User
VOC Member
Hi Martyn
easiest is machining a little groove in the shaft and fit an o-ring.
try to have the O-ring more to the outside so you have enough grease around the shaft so there is no fretting.
assemble with enough copperslip. job done.
this also works on the kickstart.
If you have a complete workshop you can also try overkill by machining the housings to fit proper oil seals which I believe is not necessary.
 

Martyn Goodwin

Well Known and Active Forum Website User
VOC Member
Actually I did fit proper oil seals to the gearbox housing so, with the exception of the gear lever shaft it is leak free.

I am wondering if I should have installed a thin felt washer on the inside of the gearbox cover, around the change shaft between the spring box and the cover?

Martyn
 

Albervin

Well Known and Active Forum Website User
VOC Member
Beware of relieving too much metal from the kicskstart shaft. A man with a big foot and strong leg tried to start my A Comet that had such a modification. He forgot which way was retard and advance; result was the shaft sheared :-( I am too much of a gentleman to name this man but is first name is ..............
 

Martyn Goodwin

Well Known and Active Forum Website User
VOC Member
Beware of relieving too much metal from the kicskstart shaft. A man with a big foot and strong leg tried to start my A Comet that had such a modification. He forgot which way was retard and advance; result was the shaft sheared :-( I am too much of a gentleman to name this man but is first name is ..............
Alyn,

no problems with the kick start shaft. The leaker is the gear change shaft.

M
 

Robert Watson

Well Known and Active Forum Website User
VOC Member
beware of relieving too much metal from the kicskstart shaft. A man with a big foot and strong leg tried to start my a comet that had such a modification. He forgot which way was retard and advance; result was the shaft sheared :-( i am too much of a gentleman to name this man but is first name is ..............

.....Robert
 

redbloke1956

Well Known and Active Forum Website User
Non-VOC Member
Actually I did fit proper oil seals to the gearbox housing so, with the exception of the gear lever shaft it is leak free.

I am wondering if I should have installed a thin felt washer on the inside of the gearbox cover, around the change shaft between the spring box and the cover?

Martyn

Hi Martyn, I fitted an O ring of small cross section between spring box and cover, I use the Penrite semi liquid grease and am yet to see a drip.

Kevin
 

Villiers

Forum Website User
Non-VOC Member
I suspect your 1/16" breather hole is too small and you may have a pressurisation problem. You say you've fitted seals elsewhere so the excess pressure can only get out via the gear lever shaft.
I mainly play with Albion gear boxes where the filler plugs include a 1/8" breather hole as a standard fitment. If tiddly Albion 2 and 3 speed boxes need a 1/8" breather then perhaps you should increase yours.
Cheers,
 
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