what about using Dassa crank and cylinders , here is a 1200 cc billet engine
Here's a start :
http://www.quaife.co.uk/shop/products/qmca2a6
It's always a bit scary when you se P.O.A.
But, there's plenty of high end gearboxes and clutches, made by quite a few companies, for non unit construction engine / gearbox usage. Chain / belt primary drive, take your pick.
The only limitation, is your imagination, and depth of your wallet.
Theres not much difference between these and aftermarket gearboxes.
You can get billet/forged harley 6 speed transmissions for under $1500 that arnt made in china.
are made for 128"+ 140hp motors.
The big issue, is packaging and the fact that once you pay for the 1500 dollar gearbox, get all the custom linkages, pulleys and cogs made to fit it all professionally crammed it into a chassis, for the same cost you could have done the following
- taken a late model sport bike transmission,
-made a mold of it and simply lopped off the front part (cylinders)
-and added the mold of a snowmobile case to the front (over simplified the process yes I know)
-then you same much time and money with engine mounting as you can now mount your big bore sled engine directly into the chassis which the engine came from.
I suppose its the same problem but two very different solutions, both costing the same but the deciding factor being where your skill sets lie. (or the skill sets of people you know!)
You actually almost gave me a brilliant idea with your post though,
I thought that a buell would be an amazing donor bike as the Harleys had external gearboxes! but sadly the buell motor has an intergral transmission which is a pitty.
Would have been amazing to mount a sled motor into the XB firebolt chassis.
Imagine how light and nimble it would have been.
Got any ideas for suitable donor bikes which already have external gearboxes?