Is it for a kid or an adult? The reason I ask is the stock engines suck, they do not last long even if you take care of them. If it's for an adult a 212cc Predator is a great engine but will even toss a grown man if not ridden with respect. If it's for a kid you may want to look at the 79cc Predator, if you take the bottom plate off it bolts directly into the stock location and they are far more powerful than the stock engine. I use briggs and strattons but I drill and re-slot the plates and have gotten good at it after doing a half dozen.