Ok i understand and thank you for your advices but please let me remind that the i never had higher temps than 100-110 Celsius and in addition the coil of the plug remains shinny and well fitted and not grey and distorted. So i believe it wasn't lean. Also i had plenty of fuel coming out of the pipe.
The same plug that didn't glow in my hands and right after one hit on the table it glows brilliant as normal. By the way i will follow your advice and check also with another igniter.
But what could be more powerful than a lipo sourced igniter?
http://www.prolux.com.tw/exec/produc...-FEATURES&lg=E