650 - 750 engine swap

I have a 650 chain drive bike and a 750 shaft drive motor, I want to use the 750 motor and keep the chain drive.
1. Is this possible
2. what are the issue with the swap.

I'd suggest putting the 750 jugs on the 650 lower. Swapping transmission components may prove difficult.

If you go that route (jugs on the 650 bottom end) you'll have to increase the size of the openings on the crankcase so the bigger pistons don't slap. Also, if the 750 motor isn't from a really early 750 you'll have issues stemming from the different types of cam chains. Most of the 750 motors used a hyvo chain while the 650's used the standard link type. The hyvo motors don't have the same cam chain tensioners so you wouldn't be able to run the same cam chain, which would lead to splitting the cases to swap out the crank anyway, which if you're going to have to do that you may as well split the cases and swap out the transmissions....

anarki650 wrote:

which if you're going to have to do that you may as well split the cases and swap out the transmissions....

Good point! On the shafty, does the shaft output bolt onto the engine or is it cast into the cases? Would it work instead to swap the swingarms and rear wheels?

If I split the cases, can I drop the 750 crank into the 650 case and put the jugs on from there?

Yes, I think, you'll just have to increase the size of the top openings on the 650 top case so that the piston skirts won't slap on the down stroke. Those don't have to be machined exact, I've heard from several people that they did it with a dremel or other small grinder in their garage with no ill effect on the motor.

I say I think because I'm not 100% sure that the top of the case is the same between the motors...