I'm usually not one to recommend a China Girl engine, but your bike is old and would accomodate one relativly easy. China girls are not the most reliable engines and can be cantankerous at times, but it is what I started out on and I learned alot from it. If it was me, I would sell your bike, and get something better with V brakes or Disc brakes and then get a Staton Inc friction drive with either the Honda GX50 or GX35 engine.