OK here goes nothing or maybe just my 2 cents worth I owned a bucket with an onan at one time and it was doing exactly what yours is doing...…..
after many hours and lots of questions I found out there is a little box about the size of a match box that is inside the motor behind the fly wheel if memory servers me correctly it is called a "STAGER" you have to bust the engine apart actully in half to get to this little devil also I think it was only about $15.00 at the Cummins dealer I sure hope this helps ya...….
Joe Harris
