Funny, I am in the "Would like to have an e-motorcycle" camp, but can't justify the cost of buying one. However, I wouldn't mind building my own. I have a small Honda SL175 rolling frame that would be good for the project, I think... and I've spent a few weeks trying to understand the components required. There's a LOT of routes to go if you're looking for plug/play options: Motor size, power, battery size, Hub drive, Mid-mount drive, and all the various controllers, etc. much like e-bicycles, but larger/more robust for a motorcycle build.
The downside is it's still pretty pricey to DIY and the learning curve is pretty steep. However, the biggest factor keeping me from actually building it is the aesthetics to make it look good--otherwise, what's the point? Most of the DIYers I've seen look like crap, if I'm honest, and those that actually look good tend to be made by professional designers with fabrication shops/access.
To me, the look is all about the battery design. It needs to fit the space correctly and look intentional (I don't want some massive square block sitting under me) and there's nothing plug/play about that. Custom seems to be the only way to go...so, until I am willing to learn how to make battery packs and form molds to fit into the frame properly, I'll probably keep burning petrol for two-wheel fun.
