I have a lawboy mower that was built in the early '90's that I am having a lot of trouble getting it to run. I can find the model and serial number if it is relevant but I don't have it handy: it says "4hp Commercial" on the tank cover and no PTO for self-propell. It has been very picky about gas since I bought it used two years ago; it won't run if I leave gas in the tank so I drain what is left over back into the can.
The first day I used it this year it fired up with just two pulls and the throttle at full choke. Ever since then though when I've tried to start it the best I would get is a quick and easy start like the first time but it dies and refuses to restart after about 90 seconds of runtime. If I try to restart it sometimes I will get one or two strokes to light off will not run.
I removed the carb and cleaned it out and also cleaned out the tank, both with carb cleaner. I also pulled and replaced the old plug, which was fouled pretty bad after just one season. Neither of those things has made any difference. I am using 87 octane gas straight from the pump mixed 32:1 with real Lawnboy oil as per the markings on the mower.
I'm handy and could follow directions, but I've run out of things to look for. Does anyone out there have a suggestion for what may be wrong with me or my engine? I'd like to keep it running if possible as I can't afford a new mower that could hold a candle to this old beast, when it is running at least :).