Originally Posted by fairracing31
You could go with a friction drive, that way you will not have to mount a sprocket. You also say you have a $300-$400 budget? Have you consider buying a nice cruiser or Mt. Bike? With 3-$400 you should be able to find a nice bike and still be able to afford a engine kit.
This is a good way to go. A hundred dollar craigslist bike and a 1 or two hundred dollar china girl kit. Allows for upgrading down the road and can build an old world, cool looking MB.
This motorized bicycle would cost just under 400 to build and thats with a new wally world bicycle. Just for illustration.