Small Engines (Lawn Mowers, etc.): Tecumseh enduro 15.5 ohv, head gaskets, engine flywheel

Question
I have a Noma lawn mower It started running really rough.When I started it I would have to keep the throttle up to keep running. The idle would go down then back up.I had to keep the throttle all the way up to engage the deck. If I droped the throttle it stalls. So I took the carb apart to clean and to see if the float was sticking and it was not. And the choke is not sticking.  Also the feul filter is clear.I put everything back together and now when I start it it still runs with the same up and down idle but now it has white almost light blue smoke. Dont really know to do now. Thanks.

  Dan

Answer
First check head gaskets and valve cover gaskets.  The next would be valve clearance.  

Before running the engine, check the oil if the level has gone up gasoline is getting into the crankcase.  This will caused by an overflowing carburetor.  That happens when the needle does not seat stopping the fuel from running into the carburetor.  Be sure to check the crankcase breeder to see if it is full of oil.  If it is clean it or replace it and replace the gaskets.  

When operating the engine, be sure to operate it at wide-open throttle.  This is an air cooled engine and the only way cooling air.  Its to the cylinder heads is by the engine flywheel turning.  The faster it turns to more cooling air you get.  Running the engine at a slower speed does more damage than good.  Best of luck.