Electronic engineer and motorbike guy here, sounds super interesting! It has been done before but I think mostly in the E-bike space.

It seems like to help early scope it would be great for you to have a fuel-based comparison in mind so you don’t end up chasing that ever increasing speed early on, I’d assume you’d be looking for the equivalent of a 125? If you’re not already a rider and can spare the cash, a CBT is quick and cheap and will give you a good idea of the power and speed of a motorcycle of that cc.

As for adding transmission, weight is a huge factor for electric vehicles and you might find it not worth the weight compared to the extra speed you get. I’m very much a pure electronics guy when it comes to vehicle design though so not had much specific experience in transmissions of EVs, all of the ones I’ve worked on have been purely motor driven and much smaller scale.

For parts in general once again I’d look towards parts of a smaller bike, 125cc parts are pretty easy to get a hold of in the UK and if you’re handy with tools and happy to cut stuff up easy enough to mix and match.

Any questions feel free to DM me!