My old lawn tractor, that I use to haul stuff around the farm, has suddenly started running irregularly. It starts right up, but runs in pulses, incre asing in RPM for about a second, then tapering off, then running high again , like a sine wave. It calms down a bit after a while but still runs with a noticeable pulsing. It ran well over the winter for hauling firewood, but with the warm weather suddenly went crazy. I suspect something in the carbu retor so I put some gumout in the tank to see if that would help. Tomorrow I'll see if I can adjust the idler screw to calm it down. Any other ideas?
It's a Craftsman tractor, automatic transmission, 24 HP B&S two-cylinder en gine.
Paul