Gs 500 e no gas intake after reaching the top speed

Hello municipality , the following problem. Our gs 500 gm51b bj.92 does not take any more gas after the highest wind speed has been reached. Sometimes the gas already collects at 160. Every now and then it then creates its 180 for a few meters and then it does not take gas again. Misignitions were already present. Passage until then without problems. Since we have cleaned gasifiers, coupler exchanged as well as various small parts is now the only thing that does not work like it sol The problem existed even before kupplunh carburettor etc was exchanged. Since otherwise it does not cause any problems we are totally overwhelmed. Has someone experienced similar or relevant references to the culprit?