I spotted this gBike on July 4th. The owner and I had a good chat. He said the kit cost $300 several years ago. It is a 105 cc two-stroke, and he says it will take him 55 mph and gets 90 mpg.

On the left side of the bike is a bigger sprocket for the gas drivetrain. The rider bump starts it by pedaling the regular power train.

A pretty good value, it seems like.