When i started up my rawn mower it was smoking very heavy checked the oil and found gas mixed with the oil what causes this

Wanda, make sure oil is not over full, oil in crankcase could be running to the intake of carb., valve guides or piston drenching an excess amount of oil on them causing the smoke. As long as mower does not smoke when driving on near level surface, mower should be OK. These engines were really not designed to cut on steep grades.
2 stroke engines, the engines with gas/oil mix are the mowers that are safe to run on hills as they will not starve or over lubricate engines. Check the attached links,instruction and guides, Good luck
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smoking at an angle
http://www.helpfulgardener.com/forum/viewtopic.php?t=37291
white smoke coming from riding lawn mower exhaust ShopYourWay

This model is a four cycle engine meaning that it does not a mix of gas and 2 cycle oil. You just fill it like your lawn mower, gas and fill the crank case with oil

Drain fuel tank. Fill with fresh and add the correct amount of the correct oil.
Take the old fuel, and add it to your car's tank, it should be diluted enough so your car will be fine.

Was it smoking before you changed oil? Did it start as soon as you changed the oil or did it start smoking a few days later?

Check the oil level again... Ethanol gas kills these Needle valves in the carburetor allowing gas to run through the carb, into the cylinders and down to the Crankcase.

Check the Oil level. If gas got past the needle valve ( which happens more and more with this Ethanol gas ruining Rubber carburetor parts) Then gas will run down the cylinder walls and into the crankcase. Gas will mix with the oil and overfill the crankcase that will cause the mower to smoke like crazy.

Sounds like the engine is tired. Blue smoke is oil burning. Hard starting is oil on the spark plugs and/or low compression. This also can be due to someone adding too much oil.
Sometimes, the carburetor Needle valve hangs u pa bit and the Crank case oil gets mixed with gas so now the oil level is high. Too much oil in a motor is bad too, that would cause theblue smoke too.

Did you put in 2-cycle mixed gas? If putting gas in it was the last thing you did before it started smoking then I would start there. Oil causes smoke and there's only 2 ways oil can get into the cylinder; mixed with gas or bypassing the piston rings. Lets hope its the gas.

You can drain it and it will be just fine. Putting mix gas into an egine that just needs gas is fine. Its going to smoke untill all the oil is burnt up. He didnt hurt a thing. Altho if you put just gas into an engine that need mix you will cause alot of problems so becarefull with that. Good luck and if you have any more questions about it feel free to email me.
A.J. Weaver

Has fuel with oil accidentally been mixed to the fuel for this mower? We have had mix oil accident get added it to this lawn mower and it will smoke a lot with 2 cycle oil.

Unless you are certain no oil is mixed with the fuel I would drain and clean the fuel system.
Replaced the spark plug with the new and replace the air filter In addition ensure you do and oil change every 30 hours using a high grade 30 wt oil to include make sure it is not over full.

Hope this tip helps.

r/
David

If this is a 4 cycle mower (seperate places for gas and oil) and you are using a oil and gas mix as I am reading from your post that is your problem. When you use a gas&oil mix in a 4 cycle you get smoke and if fouls your spark plug. Also be more specific where the oil and gas mixed is leaking from. I SUGGEST THAT YOU DRAIN OUT THE GAS&OIL MIX AND CLEAN THE SPARK PLUG OR REPLACE AND FILL WITH STRAIGHT GAS AND SEE HOW IT RUNS.

Good luck
roundo4