Alright, sorry about the delay on the updates for this but I've got the roller in, i just knurled a piece of metal, drilled a hole in the centre just a little smaller than the end of the sprocket, then heated up the knurled piece, froze the sprocket and they fit perfectly. I put a couple tack welds on just to make sure nothing would come loose. Talking about the solenoid thing, on the starter i have there's actually a separate power connection for the actual motor to the solenoid. So normally the power would go into the solenoid, then to the motor then back out, but if i just disconnect the solenoid part then it should be all good. Now I've just gotta go shopping for my electrical stuff and if everything works well I've got myself an electric bike.
