Curious, I have smoking issue on Briggs 19.5 hp and it is blue white color, runs, but barely at full throttle, dies if you lower to idle. I changed head gasket originally, and it ran great for one cutting. Put it away indoors for winter, used gas stabilizer, started it up this spring, and problem was same as before. So I replaced head gasket again even though it looked fine, same issue. I changed oil and filter, It is not overfilled, so what else can cause this situation. I looked at valves when head was off, they were clean mostly, but cleaned it even better, so I am stumped.