My Troy Built Self propelled lawn mower has a oil leak which results in white smoke coming from it. What is causing it? I had it for 3 months.

Make sure the crank case is not over full when not running and make sure the crank case breather is clear.

Your engine should take about 20 oz of oil to fill from empty.

sounds like its sucking air, check the fuel line clamps, check the cylinder head bolts and spark plug, are they tight?

You must have stored it with the spark plug end down. This has caused the oil to get by the rings and on top of the piston. Pull spark plug out and pull starter cord to clear excess oil , put plug back in . Check oil , start mower and let it run until the excess oil burns off and some of it may still be in the muffler. Mower is ok. Some body borrowed my mower and did this resulting in the same problem.

Hi , it can often be something as simple as the engine needing a oil change as oil looses viscosity/thins with use ( use correct grade ), replace or clean the oil filter and a good service or something more complex which requires a full engine stripdown like worn piston ring/oil scraper ring causing oil to flow up the cylinder walls and fouling the combustion chamber or oil leaking up through the valve stem oil seals , also storing the machine tilted can cause oil to collect in the chamber or petrol to leak into the sump causing the oil to thin.
Hope this helps , please rate accordingly

If the black smoke comes out of the muffler, you are burning excess fuel and could have an air filter plugged up to restrict air intake and cause the engine to run rich, therefor black smoke.

It is toast you fried the crank/connecting rod, by running it low on oil.
Its hard to say what caused the oil leak, but now it is ruined.

this is more severe.if you are not a small engine person 3 things get a book on mower or take to shop or get a new mower.
not trying to be funny but if you dont know its going to be hard for you to fix the valve guides are bad need to replace will take speical tools to fix.sorry

self propelled not working on troy built 675 series bought 5/08. The belt is still on.

Mowers smoke for the following reasons:
Too much oil.
Badly clogged air filter can cause oil to be sucked by piston rings.
Worn piston rings.
Worn cylinder walls.
Cracked block/piston.
Excessive blow-by getting sucked into carb. Caused by worn rings.
The only thing most people can fix is the too much oil or clogged air filter. Try those first.