A good CY (Chuang Yang I believe) engine is what you should be looking for. They come with four bolt heads which seal better over the long term, come with a better flywheel and magneto setup, and they are just built better over all. Unfortunately, you can probably expect to get about 2 gallons of use out of your $133. A quick trip to Schoharie County (Dogpile Racing) would get you a beautiful engine that will outperform the 29cc you just bought. I've mentioned them a few times already but after watching his attention to detail and the use of quality parts, I'm very satisfied with the engine I just got. They also port and polish for a bit more with huge results in power output. They race Bajas out back of their shop and those things are sickly fast.