I'm using this gear motor from Unite:
<a href="http://www.unitemotor.com/unite/en/Prod ... 9001904</a
It has a "dual D Bore" that is flat on two sides and round on two sides. It looks like this:
<a href="http://www.partsforscooters.com/127-7;j ... 5">picture
But its different. Aparently it fits a 420 chain and it has 10 teeth.
My problem is that my gear hub accepts sprockets with betewwn 14 and 24 teeth. So to make this setup work, I need to get a 16 to 18 tooth sprocket to fit the motor, and it should be sized for bicycle chain.
I could weld the existing sprocket to a 18 tooth bicycle sprocket. However, if I mess it up, I won't have any sprockets (I can't even find the replacement part).
I can potentially make a sprocket from steel on my drill press, but its a lot of work.
This is perhaps the biggest issue facing us when building our bikes. It's easy to buy a motor, and controller etc. But the we aleays NEED that ssprocket!!
How do you guys do it? Where do you look to find sprockets like mine? What do you do when you can't find the damn thing?
Thanks to all of you for all the great info on this site.