there are a lot of used motors out there for sale, all my motors are zenoahs and they work well, if you get a used one i would say replace the wrist pin, bearing , clips and a piston ring. these are high wear items in a zen and when these parts let go its bad. if you can do the work yourself its maybe 25 bucks in parts, also carbs in my opinion gum up often if you dont do regular maintenance on them, i have an exchange program with my engine builder for carbs. namba dist 11 facebook has some threads on this