Hello I have problems with the 91FX, in my club there are three friends with the same motor, but they don't have any problem (with differents prop, even one has a Bisson Pitts muffler)
But with mine I don't obtain any result, in earth it works well but in the air it begins to fail.
With some adjustments of the high needle, at the little time of flight he stops suddenly, with other adjustments at full throttle, begins to fail and to work erratically.
I have carried out the following changes:
-First I use the same brand fuel and nitro percentage that my friends used
-Change airplane (from a cap232 to an extra300)
-Try with different adjustments of the needle (the high and low)
-I have check and change the fuel tank.
-I have changed all the fuel tubes
-I have revised the height of fuel tank and try different positions
-I have revised the O-ring of the high needle, a friend also lends me a needle from his motor.
-I have put a fuel filter
-Try with several O.S #8 plugs, all new ones
-Try with different prop 14x6 14x8 15x8 all MA
I have read in this forum several topics on similar problems but I cannot reach any conclusion.

I CANNOT SOLVE THE PROBLEM!!!
ANY IDEA?
Thank you