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- Aug 6, 2005
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Has anyone converted a 650 4 speed to a 5 speed gearbox? I have a complete 5 speed clutster and am thinking of going to a 5 speed on my 70 tiger.
I'd like to use a Triumph 5 speed in a Commando. Would I be better off [strength wise] to go with the pre unit case, or cut off a unit case and weld on mounting ears? Seems it would be easier to find a T-140 where a connecting rod had done an "exit, stage right" and ruined the engine portion of the cases. Could you put me in contact with anyone who has done this?snipped
These gears also fit into the pre unit gearbox shell. I have seen Nortons running a Triumph pre unit box with the 5 speed conversion. snipped
The web link above is no longer valid. However, all the needed info can be found atTake a look at triplecycles.co.uk under "written articles" where you will find some very good info on 4 to 5 speed conversion.
The welding required to make a pre unit gearbox casing out of a unit Triumph motor would be hideous and would bring a barrel load of distortion issues with it.
Then when your done, you’ll have a very weak design, the unit design takes much strength from its holistic design and how it’s part of the engine, and how it mounts to the frame.
The best choice would be a Nourish gearbox shell if you can find one. They’re pretty sturdy affairs.
A standard 60 plus year old Triumph gearbox shell is unlikely to last in a high performance Norton.
Quaife or TTI would be a far more sensible route to take.
As if by magic...
4 and 5 speed Norton Commando gearbox
Hi all. I have a good, standard Commando 4 speed box, less kick start! if anyone is interested. Offers if you are. Also, I have all the parts to build a 5 speed unit using T140 5 speed gearing, but with a special main shaft that suits the T140 gears, but has a Norton spline to fit the Norton...www.accessnorton.com