<!-- from fixya rte -->Lawn mower is smoking white - Husqvarna Riding Lawn Mower 46 Cut Kohler Yth21k46

Most likely the valve seals or the rings are bad and the engine is burning oil.

oil has either run into the muffler or the air filter assembly clean out and good to go.

White smoke would indicate a fuel problem. The engine is flooding.
There are a lot of possibilities but the first area I would check is the carburetor float level and inlet needle.

Did you notice this after the engine oil was changed. If you overfill oil it will smoke. Check oil level. Let me know if this helped. I have other ideas, but this is the most common problem with smoking.

Hik marie carten...
Normally white smoke coming out of the exaust will me one of two things.
You have overfilled the crankcase with too much oil and it is making the smoke, in which case you can drain the excess oil out and that should elimanate the white smoke.
Or, you have a worn out engine and oil is getting by the rings of the piston and being burnt in the combustion chamber of the engine.Which means engine overhaul, or buy a new mower.
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Pull air filter see if theres any oil in it,make sure the oil isnt overfilled. Push mowers usually smoke like that if theyre overfilled,or tipped on thier side,if there is oil in filter simply take filter off,drain oil to correct level,and run it till smoke goes away. If none of this is the problem rings are probably shot. Weedeater is a cheap brand and theyre made cheap too,not made to last.

Obviously it has had oil or similar inside it at one time or another. Have you given it enough running time to burn all that out? How old is lawnmower & was any work done recently to it?

White smoke is most likely cause there is to much in the engine.. Only takes about half quart.. Clean with degreaser and garden hose on the outside..

You overfilled the oil. If the mower runs, just go ahead and mow grass until it runs the oil out of the gas tank. Or you can empty the gas tank and fill with new gas. White smoke is not a serious problem. Only a hassle.

Change the oil...it is diluted with water or gas