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Triumph 650 Mainshaft Replacement

1659 Views 3 Replies 3 Participants Last post by  TNCave
Hello all,

I have a question about replacing a Triumph 650 gearbox mainshaft.

I have a '67 bonnie engine that the very end of the mainshaft broke off of. I have been trying to sell the bike as is, but haven't had so much as a nibble. So I'm going to go ahead and fix it.

Having never been in a Triumph Gearbox, can someone offer the easiest way to get this job done? I do have a pretty good collection of Triumph tools that I've been hoarding up for a restoration project I'm planning and I have plenty of parts manuals, repair books, etc.

What I don't know, is if I can pull the clutch assembly, drive sprocket, and inner gearbox cover, then remove only the mainshaft, without disturbing the bulk of the gearbox.

Any help would be appreciated.

Best Wishes,

1 - 4 of 4 Posts
The answer is yes, you can do exactly that. You just have to be careful when you pull the inner gearbox, if you pull out the layshaft or the shaft that holds the shifter forks in place you can get crossways of yourself and screw it up. Not to worry though, it is not a very difficult job to replace the trans.
I think there might be some You Tube video's that show a transmission removal on that motor. Could help. The sproket is screwed on to the High Gear.

Look to see if the brass bush (press fit in high gear) is cracked or chipped as the result of what ever broke that main shaft, if it is, you can expect an oil leak and if your looking to resell it you might want to keep that in mind.

Good luck.

Thanks for the help.
I'll give it a shot.

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