Re: Doing my first build. HOLY COW!
A balanced crank makes a difference and an engine with one will last longer and run better. If you get a cheap one from ebay you will probably get less miles before the engine fails. These little engines are disposable but you can get much more out of them if they are ported and have quality bearings and a balanced crank. You are over 200lbs so you will need more power to get up to speed. I recommend that you look into a good expansion exhaust pipe. That upgrade will give you more acceleration and power.