Briggs and Straton 12HP Motor - Mower


Old 09-29-05, 04:50 PM
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Briggs and Straton 12HP Motor - Mower

I have a mower w/ a 12HP B&S motor. It started sucking the engine oil through the air cleaner. I pulled the head off, as well as the side cover that goes over the side of the intake and exhaust valves (this cover has a small hose connected to it and the air cleaner/carb).

I cannot see anything, like a broken valve or busted head. Before I take the motor off and tear it down to look at the piston ring, does anyone have any insight that might help?

For the record, I did not take a compression check.....yea, I know......


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Old 09-29-05, 05:25 PM
Join Date: Oct 2004
Location: USA
Posts: 255
Welcome DEERMAN,

Oil in the breather can be caused by three things:

1: Too much oil in the crank case. Check your oil level.

2: A defective breather. The pan you referred to as being connected to the carb with a hose. Replace it. Only two screws and a gasket.

3. A leaking intake valve which is the last and most unlikely cause. If this be the case you will need to check the valve/tappet clearance (.006). If OK you will need to lapp the valve and seat then sand the valve end for correct valve tappet clearance (.006).

Let us know how it goes.

God Bless,
Old 09-29-05, 05:45 PM
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Briggs 12HP Motor


Thank you. I appreciate the feedback. I will check these out and let you know the outcome.

May God Bless you!

Old 09-29-05, 06:55 PM
v8driver's Avatar
Join Date: Sep 2005
Posts: 767
also gas in the oil, of course the oil will smell it, and it will be over filled. but yes that cover is the breather, lets internal pressure go, actually isn't much for a new one if thats the case. but if its over filled, or is defective, ( has a little valve in it ) it'll let oil bypass, throwing it into the air filter and carb.
Old 09-29-05, 08:11 PM
repair_guy's Avatar
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Join Date: Apr 2004
Location: Marion,Al.
Posts: 539
Yeah,if there is not too much oil in it,then the little pop-it valve in the breather is sprung.But there should be a reason for this.

No cap on oil fill tube*cracked oil fill tube*blown head gasket*bad oil seal(s),
anything that will let excess air into the crankcase.
Old 09-30-05, 12:32 PM
puey61's Avatar
Join Date: Apr 2004
Location: Upstate New York
Posts: 3,224
When servicing the breather assembly be sure to install it back in properly. There are two small drain holes in it and they must be in the down position for it to function correctly. As repair_guy mentioned, any air leak in the crankcase can cause the problem you're having. The most common are the oil fill tube (dipstick) seal (if applicable) or the sump gasket on these series Briggs.

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