Carburettor emergency power generator HerkulesHSE 2500/E5?

The following problem: Bought a new generator and it's running. After turning it back on after 2 months, the speed fluctuates greatly, it almost dies and revs up… Sent it in and got a new carburetor, now the problem again… Did anyone else have the same problem? It's extremely annoying, because otherwise it would have…