I have a Pan with a Linkert M-74B. The engine idles well when the low speed needle is at only 1/2 turn from fully in. This seems very lean but the engine idles perfectly. When I open the throttle the engine starts missing, shoots, backfires and finally dies. No acceleration is possible. When I turn the low speed needle out to about 2 to 3 turns, accelaration is possible (when riding it still misses when I try to accelarate quickly) but at idle it's too rich, smokes a lot and finally dies.
What was already done: carburator cleaned, Float level checked and set to 1/4 (black foam float), new float valve and seat (with the rubber tip), main nozzle changed to the proper (5 air bleed hole) one, all new gaskets at the manifold, ignition checked, new points and condesor, timing adjusted, new spark plugs, different coil tested, valve play adjusted.
The fixed jet in the carburator has the number 108. Is that the propper one?
What else can there be??
Thanks for any advise!