man i got a boy go fast 49cc motor a couple weeks ago. And it is such a good engine it doesnt vibrate like the 66cc. By the way i also have one . I dont know what it is about these engines but they are a heck of a lot better than the 66 cc engines by a long shot more reliable. And seem titer than the other .Any body else having good luck with theyre 49cc ht 2 stroke engine? This is the place to brag.