Gear box # question

Hi guys. I've got a Norton with frame and engine number 220168. Its got a disc front brake. So best I can tell its a 73 750 roadster or interstate. The gearbox # is 328318. 328318 suggests the gearbox is from 75 but this bike shifts on the right side unlike the later model. Any thoughts? Thanks in advance.

I would guess know one upgraded the Layshaft bearing as needed and the original trans exploded being replaced with a later one. Maybe a late 74 pre MKIII. If your not awear of the Layshaft bearing issue use the search here & learn about it. Then you should go in & look at yours to make sure it's the safe bearing.

Certainly a possibility. Just a curious thing considering that some 75's with lower numbers have left side shifting. Thanks for the reply.

Thruxtonite said:

The gearbox # is 328318. 328318 suggests the gearbox is from 75 but this bike shifts on the right side unlike the later model.

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The gearbox shell (and possibly some of the internal parts) is Mk.3 (325xxx+) however, the Mk.3 shell (but not the inner and outer gearbox covers) can be used for either left or right shift.
A Mk.3 shell can normally be identified externally by the presence of a neutral switch hole at the front of the case (possibly blanked off on yours) and shift quadrant retained by a circlip instead of a bolt.

Thanks for the info!