Frager,


More likely than not, you have a fuel tank installation problem; not an engine problem.

A low fuel tank, long fuel lines, clunk at the front, vibration transmitted to the tank and other problems will 'advertise' themselves in what you are experiencing.


First, make sure the fuel tank's center-line is level with the carburettor's jet (+ 9 mm, or 3/8" ), with the model in level flight attitude.
If not, correct this before going any further.

Also, make sure the tank is as close as possible to the engine; the fuel line from the tank to the needle should not be more than 2.5-3" long.

After that, you can adjust your engine perfectly.