Thank you so much "Wingracer" ok "Chunk t", The engine is a O.S. max21VG Series with 3 ports and 3.45cc Displacement, 16.6mm Bore 16.0mm Stroke, 2.0 ps/30,000 rpm.
Maybe the head clearance is ok. but every time the race is over 40 minutes, the engine works very good but when i remove the glow plug this is burn out, is this normal?? the carbon deposits are normal?? we use these engines with shim and a glow plug #8 becouse this are the factory items,but maybe these are calculate to run at sea level.

Help me or tell me its ok.

A lot of thanks again