The Short answer is, "Yes it will."
Now, I never done this myself, but if you go to motorbicycling.com, there has been a few people that has done it.
Now assuming you can cut and weld, some obstacles to overcome are :
- Matching the transfer ports (may be doable without, but not optimal)
- Flipping the piston (this is to avoid the ring gap biting into the ports)
- Fabricate a new intake manifold
- Route the exhaust
- And if you have a slant head, flip the head ALONG with the jug so that the spark plug points towards the exhaust, like it is stock.
Only thing that I don't know would be the magneto. I'd assume it can be left untouched since it has no mechanical advance.
Essentially, all the action is happening on the jug and the head.