I have two blue heads and one older version and they all start and run without issues,just breakin per instructions and fly no fiddling with settings, never had a flame out cant say that for a few of my os and saito 4s's, these engines are without doubt the best value on the market, watch for Hooby people's sales events and you can get a new engine at below used prices of the other guys, i bought a 52-4s at the toledo show and a 91-fs online before the sale went off, dont get much better than this..