Bench-testing first, if the engine still runs unsteady, cutting off the needle valve assemblyand mount it in the front of the fuselage would be actual

If I dont remember wrong, the engine ran almost identical unsteady when I had it in my big stick 60, the first plane it was used in.

I have been looking for faults many times , but havent found any fault. Changing plugs, replacing fuel path, tighting screws, remove dirt from the needle valve seatdidnt solve the problem.Ive been flying model airplanes in over 20 years, so I have some Knowledge

So, theneedle valve assembly/heatingproblem looks logical for me </p>