ORIGINAL: fadi81
Following the advice of many here, I switched to an 11x6 propeller which is supposed to be the ideal prop for this engine.
Now All I can get with 5% or 10% is 10500 to 11000 RPM max. It is still pulling my plane but I am not having unlimited verticals with the Sig 4star and it is quite slow for my taste (I moved the engine from the trainer to this one)
I tried a new #8 glow plug and still had the same result. Tried an 11x7 and 11x8, it was faster but loaded the engine even more to the point that I barely reached 10000 RPM.
Fadi,
It would seem something is wrong with the engine.
See what [link=http://www.rcuniverse.com/forum/m_4432418/tm.htm]other people are seeing with this engine[/link] on different prop sizes.