triumph 650 5 speed conversion

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 think it is like in my 69 Trident..just drop in there!
philippe

I thought there were a few variations of the 5 speed and am unsure if they all fit the same or of modifications would need to be done, thanks Phillipe.

I have done this a few times before. It is pretty easy to do. The Triumph 5 speed is a nice gear box. 1st is slightly lower so you can run taller gearing so that the engine doesn't need to run as fast on the highway. The gears shift easier on the 5 speed, because each gear is closer to the other gears. There is less of a jump between gears. 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. You will need to open out a hole in the inner cover. This is only for clearance so it can be done with a file or die grinder. The important thing to get right is the movement of the gear lever. The gear lever on the 5 speed moves through less of an angle than the 4 speed. This is done on the bikes that come from the factory with a 5 speed by having the outer cover machined differently so that the gear lever moves less. You can modify your outer cover. The simplist thing is to get a 5 speed outer cover.

if you don't do something to limit the gear lever travel you will shift from one gear to a false neutral between the next two gears intead of the way it should work. You don't want that. I think I know this from doing it the wrong way the first time. That was a long time ago so I can't remember it that well any more.

Yes that is very true the whole shift mechanism inner and outer covers are different and not by anything you could see with the eye. All of the 5 speed bits need to be there re- mounted into the covers. The new bits will fit the pre-unit as well. Little .020 differences in little parts make huge differences in the distance of each shift.
Another thing about this each gear has a set of part #'s punched into their sides be sure you are not using a cast off set of gears from the early bikes with straight dogs or you will be very disappointed with the box.

That is excellent to know. I'll start looking for a late model cover, thanks for the heads up.

Take a look at triplecycles.co.uk under "written articles" where you will find some very good info on 4 to 5 speed conversion.

tricatcent said:

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

Click to expand...

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?
Charlie K

pdl999 said:

Take a look at triplecycles.co.uk under "written articles" where you will find some very good info on 4 to 5 speed conversion.

Click to expand...

The web link above is no longer valid. However, all the needed info can be found at

http://vintagebikemagazine.com/tech...ating-of-a-4-speed-to-a-5-speed-transmission/

Charlie K

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.

Fast Eddie said:

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.

Click to expand...

I suspected as much.

Fast Eddie said:

The best choice would be a Nourish gearbox shell if you can find one. They’re pretty sturdy affairs.

Click to expand...

Probable the best choice, if one can be found.

Fast Eddie said:

A standard 60 plus year old Triumph gearbox shell is unlikely to last in a high performance Norton.

Click to expand...

My only hope there would be to have it cold stabilized.

Fast Eddie said:

Quaife or TTI would be a far more sensible route to take.

Click to expand...

Those are to rich for my blood.

Cold stabilising might work.
As might fabricating a Maney style mainshaft outrigger.
The shafts bending / flexing and then acting against each other is a primary reason for gearbox cases failing IMHO.
I have also wondered if sturdier ‘full cradle’ type gearbox mounting plates might help provide some support and stiffness to the case as well, rather than the flimsy open ended affairs common on Tritons etc.

As if by magic...

Fast Eddie said:

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

Click to expand...

Thanks for the quick "heads up". That said, I've already sent him a PM, received a reply and sent another.