Jim, I had a fussy .74 and cured it by countersinking the glow plug so that the entire idle bar was inside the combustion chamber, I have three of them now, two ringed and one ABC. They all three would turn a Graupner 12x8 two blade at 11,200 rpm, the ABC one is now a Diesel turning a Graupner 12x8 three blade at 9,400 and improving. The ringed ones ran much cooler than the ABC one when all three were glow.