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What Would Cause My Briggs Stratton Murray Lawnmower to Leak Oil Through the carburetor My riding lawn mower was blowing oil bad out the carburetor, After a long and hard search here is what i found caused problem fixed the problem. lawn mower crankcase breather i replaced and fixed all.  If you are thinking I do not know where exactly the oil is coming from, but it is running out of the carb area and into the air filter and prefilter then out of the housing. It could be coming out of the breather, but I checked and the breather seems like it doesn’t have any oil in the tube or the piece that covers it. Also none comes out while it is running. There also seems to be oil on the bottom left cylinder fins and linkage area, which lead me to think the OHV cover although that could be from the same leak. coming out of carburetor lawn mower The only way oil can get out of the carb. is to come out of the engine past the rings, valve guides or through the breather tube or leaking gaskets. However because the engine is constantly drawing air into the cylinders it is uncommon for the oil to come back out the carb. unless there is a large quantity or engine crack case breather is bad. It almost sounds like there is an oil leak that is spraying oil on the air cleaner area and maybe drawing a little oil in while running?  Lawn mower leaking oil from air filter tipped lawn mower oil in air filter If you tip a lawnmower greater than 15 degrees with its carburetor pointing downward, then oil can leak from the crankcase and into the breather tube. The breather tube is connected to the carburetor, which connects to the air filter. Tipping may occur while you change or sharpen the lawnmower’s blade or clean the bottom of the mowing deck. Mowing grass on slanted ground, such as mowing across a hillside, can tip the mower enough to allow its oil to flow toward its carburetor. Tipping the lawnmower so that its carburetor is on the high side helps to avoid the oil problem. Overfilled Crankcase Lawnmower crankcases are typically small, often requiring less than 1 full quart of oil. An overfilled crankcase pushes the excess oil in any direction the liquid can move. Although the excess oil often ends up in the cylinder, it also can move into the carburetor and out through the air filter. The best way to avoid overfilling a lawnmower with oil is to add a little oil at a time, and then check the oil dipstick to see whether or not the oil level falls within the safe range, above the “Add” mark but not above the “Full” mark on the dipstick. I think I found my leak, as I don’t think it leaks while not running, Though I am not sure. I will be keeping a close eye on it though. I think my leak was caused by a clogged breather in combination with not having a fuel shutoff. There was oil laying in the breather and not draining out through the hole that leads back in to the crankcase. you see oil leaking outside the engine is not what is getting in the carb, but it is an indication that you have a leaking head gasket. Since this engine is overhead valve, a leaking/blown head gasket will blow compression gasses into the engine crankcase. These gasses have to vent out of the engine. The crankcase vent goes to the carburetor air filter housing. That’s how the oil would get in there. How do you get the oil out of a lawn mower carburetor? Shut gas line off, then remove any plug in the carburetor, or remove the bowl, and just rinse it out with a spray can of carburetor cleaner. Or just turn it upside down over a container that will catch the oil, and leave it at least an hour or so. Blocked crankcase breather symptoms  What is a Crankcase Breather? it’s an external part of the engine in charge of ventilating the crankcase. If you don’t know, the crankcase is the part of the engine where, among others, engine oil is stored. Even small push mower have the crankcase breather deep in engine. While engine is working, a certain amount of gases caused by combustion (better known as ?blow-by?gases) manage to pass the piston rings and enter the crankcase. These gases then cause a pressure build-up in the crankcase, which if went unattended, can cause serious problems like gasket leaks, the engine burning oil, or even worse damage the engine. When the crankcase breather goes bad you get stoppage or oil blowing in carburetor In my case, these symptoms appeared over a certain period (almost a month). what happened and in what order did the symptoms appear. These are the symptoms in chronological order: crankcase-breather-problems-rough-idling ROUGH IDLING. The engine worked flawlessly until I noticed that sometimes the idling became rough for no apparent reason. … OCCASIONAL LOW ENGINE PERFORMANCE. … OIL LEAKS UNDER THE mower. Briggs and Stratton oil coming out of breather tube Make sure the engine crankcase is not over full with oil. If that checks out, have a look at the breather assembly, and make sure there are no air leaks into the crankcase. If all checks out your problem maybe a bad crankcase breather. What are the symptoms of a blown head gasket in a lawn mower? To diagnose a blown head gasket, look for certain troubleshooting signs. Low Power. Low engine power in a lawn mower can be caused by wear and tear, lack of oil or regular maintenance, worn-out seals or a blown head gasket. Failed Compression Test. Diminished Compression. Oil Leak. Lawn mower oil in cylinder Pull the dipstick and if it smells like gas then gas got into the oil, which caused it to over fill and maybe went through the crankcase breather and into the cylinder. Blow out the cylinder as good as you can-change the oil- put it outside and let it smoke bad. If it won’t stop smoking then you probably have bad piston rings or the rings are all lined up. small engine blowing oil out breather If the engine has oil leaking from the air filter, I recommend checking the oil level first. If the engine is over filled, it will blow oil out the breather into the air filter. To cure this you need to drain some of the oil so it reads full on the dipstick. Then remove the air filter and wipe up all the spilled oil. Once it is cleaned up, leave the air filter out and start the engine. The engine will likely smoke for a few minutes. Usually 5 to ten minutes. After the engine stops smoking go ahead and install a new air filter and it should be ready to go. |