Small Engines (Lawn Mowers, etc.): Generator Revs while Idling and Under Load, volt generator, well pump

Question
Greetings.  I have a Craftsman 2500w generator that has very low hours. It has a 6hp B&D engine. Recently, this 120v generator was used (not by me) to run a 240 well pump for about 3 minutes.  Since then, it is producing current, but it the engine is pulsing while idling and under load.  Do you have any thoughts or suggestions?  Thanks for this excellent service.

Answer
a 120 volt generator  does just that  produce 120 volts,  ONLY!!!!!   if it was hooked up  and tried to run a 240 volt pump????   it may have harmed the output diodes in the generator and thus causing your problem.  basically it doesn,t know what to do .  (ex.  am i underload?  or am i not??)