I have the stock 26cc Zenoah but it's dead (long story)....I already have the Jetpro pipe but by the time it got here the engine was no longer in running condition. Anyways I think I'll either go with the stock 26cc Zenoah again or the 27cc head kit engine from OneillBrothers. I'll check prices on the 26cc Zenoah and go from there.