Hi so I have a cheap China girl 66cc with the internal cdi that's broken in and has good power down low but is running like crap on top end, only getting 24mph out of it. I know me and my bike are quite heavy so I would like to get a new stronger motor with external cdi but not sure which I should go for. I have about $600 budget but don't really want to spend it all on a motor but I could. I'm looking at the dax little evil motor, Jake's speed racer, or the most expensive of the bunch the arrow 5hp motor. I'm looking for recommendations on both motor and cdi. Thanks