Well, I ride a bike and drive a turbo'd car. From my experience I definately wouldn't want a turbo on my bike. Changing gear on a bike is different from a car. It happens almost instantly, so there will be no time for the pressure to vent, so you wont get noises like you get on a car when going through the gears. Most importantly though the characteristics of the power delivery are completely unsuitable. I'm very rarely at full throttle on the bike. If I did that then the front wheel would fly up in the air, on a turbo'd bike you'd then have to release the throttle, venting to atmos and going back off boost. Plus the surge you get when you hit boost pressure could be dangerous. Just totally unsuitable. If I wanted to go faster then I'd just get a faster bike. Its not as if he's at the limit of performance as far as his budget is concerned.