I set about taking the engine apart and out of the frame. Everything came off fine, except for the flywheel -- notoriously hard to remove. Since the crank was pooched anyway, I wasn't too concerned about it, but I ended up dropping it off at the Yamaha dealer, with instructions to remove the flywheel and split the cases. The plan is as follows:
- install new OEM crank, bearings, and timing chain
- purchased used OEM cylinder and a HC 125 or 130cc kit, OR complete BBR 150 kit
- get flywheel machined and lightened
- purchase oil seal kit
- aftermarket exhaust system
I need to be careful, as one could spend thousands souping these bikes up to a staggering 17hp! Surprisingly, the risk of buying a used OEM cylinder, getting it bored, and then buying a 125 or 130 kit would be the same cost as a complete 150cc kit, so I think I might go that route. The carb would likely benefit from some richer jetting... my goal, of course, is to make something that would give 200s, 225s, or even 250s a run for their money on the ice...