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a.m.c./norton gear box

stumpy lord

Well Known and Active Forum Website User
VOC Member
Hi all,
I have just acquired a norton/ a.m.c. gear box for my next project, and find I know nothing about them. is their any body out there that has an exploded diagram of the said box/over haul detailes, size of sprocket to use for a comet. Any help gratefully receaved.
stumpy lord.


Well Known and Active Forum Website User
VOC Member
Norton Box


Talk to Dad when he gets back from the Continent this weekend. He's just gone through the mill with this issue. From memory, the best box to use is from a later Commando having the longer mainshaft. I think the serial number prefix is NA followed by a load of digits.

Peter Barker
Bristol, UK

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
Norton boxes

The main difference is in the length of the mainshaft. Manx boxes have shorter mainshafts than boxes for twins. (Short mainshafts are less prone to bend and cause jumping out of gear.) I've had 4, 5 and 6 speed clusters in the same shell over a 12 year period. Send me your private email and I'll send you a Motorcycle Mechanics "how-to" on how to strip and rebuild them.
A friend of mine says there's no hassle. Tip the internals into a washing-up basin. There's only one way they'll go together and work, so all you need to find it is patience.......I merely pass this comment on........
One fact not mentioned is that if you knock the camplate off its spindle and replace it back to front, one down, three (or four, or five) up becomes the reverse. Also not mentioned is that anything from ATF to SAE 40 is OK. I've used ATF for yonks with no problems.
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Photos from the 2022 North American Rally

Photos from the 2022 Annual Rally

Photos from the 2022 French Rally