As for the original question, no, there is no motor that fits in the C50 frame, other than the M50 motor. The M50 motor is very similar and it makes the same power, so there is no benifit to this swap. The C90 motor is too tall, long, and fat to fit in the C50 frame. You could spend a boatload on mods, but in the end your C50 is still going to have less power than if you simply trade up. Take momma for some real long rides, going a full tank without stopping. When she complains about not being comfortable, take her to the dealer and have her sit on a C90 or C109 to show her the extra room on a bigger bike. Trading up will sound like a much better idea to her then. :bluethum: