I just changed the piston rings on my tecumesh sears mower 917.372201. When i try to start it, exhaust comes out but their is also fresh fuel coming out the exhaust hole indicating the mixture is too rich. I dont believe its the carb because it worked fine when the mower died from loss of compression. I wasnt sure about the timing but i finally got it attached and i checked and valves open at proper times. except that they open slightly earlier than they should. Why is it getting all that fuel in the cylendar? I think its the timing but i dont know how to properly set it if anyone knows please tell me how to set it correctly.