It sounds as if you have trouble shooted any issue the engine might have so move on to other parts of the equation .


My thoughts are that the problem is the fuel .

This is exactly what happens when you either have an old bottle of fuel , a really low nitro content fuel (like 5% heli) or your engine is grossly mis shimmed .

Try a fresh bottle of byrons and let me know what happens .

Remember this , just because you get fuel from your lhs doesn't mean its fresh , they could have left it sitting in back on a concrete floor for six months before you bought it and that is not good !!


Btw , I am no guru , I just know a few things