After an oil change and new spark plug my Craftsman 3.5HP mower now has a missing problem. The engine runs but the miss is annoying. The mower model number is 917.383165. The engine model number is 143.943508. I have checked the plug gap and it is at .030". The mower is stored indoors. The gasoline is fresh. The owners manual advises the engine speed is factory set, the carburetor is non adjustable. I would appreciate any suggestions to cure this problem. Thanks.

tecumseh? does it miss when it gets hot, or all the time right from startup? also does it blow any sorta smoke out the exhaust?

Bugman, I am not sure who the maker is. How do you determine that? Missing starts after a few minutes operation. Not right at startup. There is no smoke. Thanks.

Sounds like you have a electrical problem if you dont have any smoke. check your condenser points under your flywheel if you dont have a electric amature. Also check your spark plug wire cap where its connected to the spark plug if it's leaning really close to the engine then every time the spark plug fire it will cause a short and cause the engine to backfire. If this is the problem you will see a small spark from your spark plug wire cap to the engine every time your spark plug fires.