ORIGINAL: jetpack

If the crank is soft enough inside, you might be able to tap into it, then just use a screw like the TD does. Looks like a short run for inside threads though. This is not where a hollow crank is to the advantage.

Wish there was more of a nose on it. That carb extends way past the front of the case. Another tease of what would be a good engine to use past it's engineering for cars. I've been watching for something to convert to marine use with a machined water jacket head, and room for a dished back flywheel. They need to make it more generic or universal in that respect.

It looks like a good, high winding motor otherwise.