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What gearbox for .........

Comet

Well Known and Active Forum Website User
VOC Member
Does anyone know what gearbox would be good for our section sprinter? It is currently fitted with a standard Burman which is obviously quite slow. I know people use Norton boxes as an alternative but I do not know which one.
Any help would be great.
Thanks
JK
 

roy the mechanic

Well Known and Active Forum Website User
VOC Member
you will not "better" a norton/amc 'box. they were fitted to an embarrasment of this marque. singles, twins from the 50.s onwards. commandos had a longer mainshaft to facilitate an outrigger bearing to beef up the primary drive. i doubt you will need this on a comet! close ratios were available for manxes+ G50 matchboxes.
 

ET43

Guest
The sprinter will need to adopt a Commando box and for which you will find mounting details in MPH. The earlier AMC pre Commando box has different mounting lugs and needs the F106 lower lugs dropping by 3/4" to pick up the top lug of the gearbox. I have a long shaft in the tricycle special gearbox and where the clutch is pulled up against a stop in the centre of it's body. Not as on the Commando against a circlip on the shaft. The material behind the AMC clutch on the inner chain case will need facing off as the clutch body scrapes it. The gearbox sprocket is pulled up against a hardened sleeve which forms part of the oil seal. The sprocket can be spaced out by using a large thick washer if so desired. If you run a 22t GBS you will need to dress the left hand lug on the F106. A good chap to find is Dave Coates of Upper Buckleberry near Thatcham, Berks. P.M. or ring me for his number. Cheers, ET43
 

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
Any "AMC-type" Norton box, as fitted to Dommies and Commandos, distinguished by an oval outer casing with the long axis horizontal. They are all substantially identical inside. You can fit a four, five, or even six-speed cluster inside - it's a remarkably versatile casing! You cannot however fit a set of close ratios AND retain the kickstart.
Somewhere I have some dope on fitting a Norton box to a Comet. The main difference from the Burman is that the Norton box has the tensioner on the top stud, pivots on the lower, and the Burman is the reverse. If you sent me your personal email I could go dig it out.
Does anyone know what gearbox would be good for our section sprinter? It is currently fitted with a standard Burman which is obviously quite slow. I know people use Norton boxes as an alternative but I do not know which one.
Any help would be great.
Thanks
JK
 

Black Flash

Well Known and Active Forum Website User
VOC Member
+1 for the Norton Commando box. if you are not trying to transfer too much power through the box there is no outrigger bearing necessary and the extra length helps you with the wider cast alloy chaincase of a Vincent against the thin tin ones used on earlier Nortons ( hence the longer shaft). in exteme cases, you could use a larger engine sprocket to increase g/b speed and lower the torque trough the box while you will loose a little bit (negligible) of power by doing that.
Late Commando boxes also have a slightly higher gearing which would be good anyway I suppose.
 
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