Motor fires up fine runs slightly rough for about 10 seconds then smooths out for about 5 seconds and cuts off. Will start right back up after about 5 seconds and does the same thing. I have drained the year old gas out and put in fresh. What am I missing. Thanks.

Previous owner had way overfilled crankcase oil. Oil had gotten into carb and clogged air filter. Drained oil to correct level. Ran engine but kept cutting off-see above. Took off carb cover cleaned housing and ran without air filter-ran fine. Unsuccessfully tried to clean air filter with gas-did not work. Apparently, the engine could run just long enough to exhaust the air in the old filter and cut off which is why it would start back up after a few seconds. Bought new air filter-whole thing-about $15 at Carquest. Put in some carb cleaner and installed the new filter and it runs perfectly.