RV Repair: generator, onan marquis, pace arrow

Question
I have a 1996 Pace Arrow with an Onan Marquis 5000, Lately only under load, it has started surging (rpm going up and down) if the load is high enough it will actually stall. I have always changed the oil,oil filter and air filter regularly. I have used the Onan decarbon spray once. It has about 1200 hrs on it.

Thanks in advance, George  

Answer
Mine does the same thing and it drives me crazy.  I have tried readjusting the choke and it has helped a little, a new spark plug gapped properly helped a little more.  One problem that I have heard of lately is the shelf life of gasoline, now about 30 days as opposed to 6 months in the past.  Since RV's are usually not run much, a fresh fill of fuel might go a long way toward solving the problem.