RE: hyper 7 - super good ||| hyper .21 not so good
there is nothing wrong with most rtr engines. its almost all the time inexperienced drivers. ot saying that you are at all. ive had a force .26 for 8 years and still have the original sleeve and piston. the thing is still my fastest rc. sounds like a flaw like another guy said, sand in the engine. do you clean your filter often. or just a bad tune job. hope you have better luck next time.