Hello all. I have been reading this forum and a couple of others trying to get some answers on a couple of specific questions. My apologies if I have missed the threads that would have answered. We are looking at an MX500 for my daughter. We wanted the MX650, but none used close to us. I'm looking at ways to get a few more MPH top speed out of it, nothing crazy. Since everything I read says they are basically the same bike except for the motors, can't you simply put a 650 motor in the 500? If not, why? The other question is more of someone's personal experience. For the under 100# weight, would going to a 14 tooth front sprocket, or a 55 tooth rear sprocket, or a 13 front and 65 rear, bog it down too much at launch? The bike will be ridden on a flat paved road 99.99% of the time. Thanks in advance!!