Newer Centurion 3250 generator, white smoke

My father in law brought me his fairly new Centurion 3250 generator. It has very little use on it. He said it started smoking and wanted me to take a look at it, not that I'm better than a real mechanic, just cheaper! Anyway, I gave it a once over. I started it up, it ran fine, no smoke at first but then a steady, light smoke from the muffler. Seemed to look and smell like a whiter smoke than blue, more like a mixture of white and blue, but then again it was night time when I checked it. I drained the fuel and dropped the bowl on the carb, all very clean. I took off the valve cover (OHV) and checked the gap, they were both pretty loose so I set them at the proper clearance. I checked the spark plug and was surprised that it was pretty fouled considering how clean everything else was. I cleaned off the plug, checked the gap and put it back in. I checked the oil and it seemed way overfilled, running out of either plug when removed. I drained out a little of that oil until it was halfway between the H and L marks. I couldn't find anything major that stuck out to me. There were no adjustment or mixture screws on the carb. I started it up and it still ran fine, no smoke at first, but then it started again. The longer it ran the heavier it got, still not a whole lot of smoke, just noticeable. I noticed that when I manually bumped the throttle to higher rpm's the smoke cleared out briefly, but then started again when it was at normal running rpm's.



My father in law is pretty meticulous with his tools, he always kept fuel stabilizer in the generator when not in use, always kept them in the garage, etc.



I wish I could give you the engine info, seems like these days they don't want you to know anything about the engines they use. It looks like a generic 10 hp horizontal shaft OHV engine. Similar in setup to a Robin or LCT. Hopefully the engine details won't be necessary, this seems like a pretty general problem.



Any help or ideas would be greatly appreciated.