a few people have put electric hub motors on the front and used it to start the engine, and then have hybrid drive the whole way. sort of a similar system to what you get on a prius
Wish someone out there would make a key start system for 4 stroke engines. That would probably require a whole nother transmission mounted on the pull start side of the engine connected with a motorcycle starter motor. The way a key ignition works is it's basically an on/off switch connected to a key hole wired to an electric motor hooked up to the ignition coil. This would be possible on a motorized bike but it would probably be expensive & heavy.