I have been investigating cheap transportation for my four mile trip to work each day. SUV mileage just isn't cutting it. I am looking into 49cc chain driven motors for my bicycle. My boyfriend is concerned the life of the motors would not be very long or that the motors would not be good for an eight mile round trip five times a week (flat rural roads). He's an auto mechanic but just doesn't know much about this type of motor. What motors would you guys recommend for a beginner for my transportation purposes?