I have a 8yr old Craftsman lawnmower with an B&S 6.5HP Quantum Series engine that up until today has been running great this season, one pull and she starts no problem. This mower had its general beginning of the season maintenance done on it at around the first week of may, new air filter, NGK spark plug, AMSOIL ASE SAE30, and it always gets fresh gas that has a splash of seafoam in it to keep the engine clean. I have a large property, it usually take me between 1 to 2 hours to bag the whole lawn. Today after about 1 hr of cutting and bagging I stopped to empty the full bag into the trash can, went back put the bag on and gave her a pull and nothing...wouldn't turn over. After about 5-10 good pulls the engine finally turned over but it was chugging for a few seconds with slight puffs of white smoke coming out of the muffler before it completely got up and going again. I was able to stop and start the mower 3-4 more times without any trouble before it wouldn't start again and it took another several good pulls to finally get it going. but when I can get it started it runs fine and continues to run perfectly until I stop - Start it again. What could be the cause of this? it only seems to happen after the machine has been in use for awhile? Some dirt going through the carb, charging system, or something as simple as a bad plug?
Good luck, been working on mine all day, exact same problem engine and all. I was hoping I might find the answer here. I'm 65 and have been working my own mowers since I was 6 and can't figure out what the problem is.
