Looks like you will need to make a special mount of some type or if you don't care about chopping and welding on your bike, weld in some tubing to make you a nice engine mount. I think you have the start of a nice bike. With a welder you can motorize almost any bicycle.

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norms-iron-works.tripod.com
motor assisted bicycle engine headlights that work off of your white power wire. check it out