Just finished my first 4-stroke. Started with a new BCA Charleston Cruiser bike (built in South Carolina). Replaced seat with a sissy bar and banana seat, changed out handlebars for some mild ape hangers, plus some lights, bar bag and computer. Bought the motor kit from motorizedbicycles.com. It's the same outfit that operates motorizedbicycles.ca in Ontario. I am very happy with them so far. They offered a good price on the kit, and have been very responsive to my questions and concerns.
Breaking in the engine easy, so I didn't go very far or very fast on the test run. But it seems to be running very well so far.