small engine/generator help

I’ve had a little 3500w generator for about 12-15 years that I keep around the house. It’s a knock off brand I bought from Bowie whenever I was in college. The thing has always run incredibly well for what it cost and I stay current on maintenance with it. I only use non ethanol fuel and I always stabilize and run fuel out of the carb before storing.

Today, I was cleaning out my garage and I cranked the generator just to run it for a bit. Haven’t cranked it in several months. It cranked fine on choke, ran fine, but then shut down after about 30 seconds. I repeated this about 6-7 times and got the same result.

Looking at it, I noticed there was a bit of oil in the air filter. I pulled the filter out and noticed that it seemed like a little bit of oil was collecting at the bottom of the filter insert. I pulled the plug and it was pretty fouled, so I sanded it down an bit and put it back in. When I cranked it again, it ran fine for about 2 minutes, then shut down again. When it was running, it was purring.

I don’t particularly need this thing anytime soon, but I like to keep all of my equipment in good working order so fixing this thing is going to be a project of mine this week. I’m not a mechanic though, so I come to the OB small engine gurus for direction. What say you?

TIA.