The plug looked nice and gray. Slight leak of oil between exhaust and cylinder but not much. I had pulled apart the carb and all passages were clean. I am suspecting either a vacuum leak at one of the seals or a coolant leak at the head dripping onto the piston. I should have replaced the piston and ring earlier and I am learning the false economy of stretching the time on replacing them. If anything the engine smoked a little less than usual. I did drop the needle half a groove but the outside temperature was hotter than usual. I don’t think it was a lean stick due to the carb settings…. maybe elsewhere but not the carb. Motor temp was up to about 170, radiator temp 150. Above ideal but I didn’t think dangerously high, and that was in grid before actually starting my run. Could an old piston fail in this way or did I kill it?
The one thing I did notice is that when I would spin the wheel to start the motor it felt… rougher…. Like not enough oil. I was running the same ratio as always, a different brand, but I don’t really believe that the brand would make that significant of a difference. At the previous event there was just the slightest hint of a stumble when snapping open the throttle. So I think it was a problem that got worse quickly but progressively.