Dave - About 4-5 years ago
Drakman and I bought two Draks that were CVT set ups and were going to try and swap motors to either snowmobile or bike engines. Switching the top shaft o the trans to a sprocket requires the whole transmission to be dismantled and a new top shaft to be made or swapped out. The gears are very expensive, expect $4-500 min US to have the this swapped to something that would accept a sprocket. Swapping the lower flanges would be much easier. However, if you go to 930 flanges then you'll need to swap the drive axles. The flanges should run less than $100 each of you can find a local shop that would make them. You could contact Alain for a set too but he may charge a premium for them. The problem you'll have, unless you modify the axles too to accept the 930 flanges, is that going to a solid shaft will plunge too much into the CV on older Draks and cause binding and extensive wear and damage of your CVs = counterproductive. The suspension geometry will not support using a solid axle, that is why they are set up with a Citreon 2CV shaft that will telescope. The newer larger Draks (Tiger, Tornado, etc..) have entirely different suspension geometry that works great w/ solid axles and Porsche or Audi CVs.
So, for the lower end of the trans you'd need new flanges, new CVs, and new axles or have the the flanges of the axles modified on a telescoping axle set up if you have an older Drak. If you try to swap to solid axles, be careful, as the plunge will bind/damage CVs/flanges at the hubs which will need to be modified as well. Botom line, it is not recommended.
If you're swapping engines for anything considerably bigger, the only change I've seen that works is using a large snowmobile Engine. Even then compromises have to made. They're wide compared to bike engines and the output via a CVT belt will need to offset to align with the centered Drak F-N-R gearbox box/reduction. Snowmobile engines output at the far edge of the
Engine while motorcycle engines have the output via chain closer to the center of the Engine and more adaptable to the Drak F-N-R box.
Lastly, I believe the gear reduction ratio inside the Drak transmissions are different between earlier CVTs and late model chain drives. Getting a proper reduction ratio for the Engine set up would require either an entirely new F-N-R box or new internal gears. At that point, it will be significantly easier to just get a new F-N-R box which will run anywhere run about $3,000 vs trying to figure out the proper gears and then having them made to fit. Also note, on the newer chain driven transmissions that are designed for higher powered engines the gears are wider, stronger and thus there is no neutral (neutral is obtained off of the bike Engine tranny).
When we did all of this research a few years back we figured it would take thousands to swap an Engine, several thousand more to get the transmission set up to handle a modern fuel injected high-power Engine and would have to deal with a lower drive train that couldn't handle the power and we'd be replacing CVs and/or shafts regularly.
Any questions, let me know.