Ade said:
Seems like I was wrong about this according to Luna - there is no 73mm specific version just a 68-73mm.
That is what Luna says, but Bafang's site says different, and I know from personal experience that the "68-73mm" motor that they sell cannot be directly installed onto a 68mm bottom bracket. I think the difference is in the bolt mounts for the motor mounting plate - the 73mm motors are cast 5mm fatter. I have a new Motobecane 529HT, which has a 68mm BB - the motor can't be installed at all without shimming the motor shaft the full 5mm on the drive side due to the geometry of the motor mounting plate. Unfortunately, the motor shaft and spindle is ideally centered for 68mm, but offset to the drive side with a 73mm bracket. The required shimming for 68mm creates twice the offset that the 73mm has, so it is worst of all worlds.
Also, the motor shaft doesn't fit through my 529HT bottom bracket - it's pretty close, so I might try sanding down the motor shaft a bit - it'll probably go without a whole lot of work, but i have to decide if I want to hack up the machine, or I just pack the whole thing up and send it back. I'm on the fence. If I wanted this kind of project, I would've bought a Cyclone.