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I have a 718 that runs fine but sucks oil into the air breather which then clogs the air filter. if a put in a new filter it runs fine again for a few hours until that filter gets coated with oil. The dealer will only tell me i have to bring it in for them to diagnose. can't afford that. =) im sure its a simple fix once i figure out what to fix...

Most likely causes are blowby. Which could be worn, bad rings, blown head gasket, or possibly a broken breather reed. Which engine do you have on your mower. Model number helps us to narrow down the possible issues.

it has a Briggs, Vanguard 18hp gas Vtwin engine. model number 350447 there is a crankcase vent in the middle of the air filter where it sucks the oil from.

The breather housing is located under the air cleaner attached to the block with a single bolt in the middle of the V between the cylinders. that is were the breather reed is located. Other reasons for your issues could be a blown head gasket or worn, broken rings causing pressurization of the crankcase.

ILENGINE said:

The breather housing is located under the air cleaner attached to the block with a single bolt in the middle of the V between the cylinders. that is were the breather reed is located. Other reasons for your issues could be a blown head gasket or worn, broken rings causing pressurization of the crankcase.

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i found the breather and took it off, cleaned it, it appears to be fine, gaskets are still pliable and not brittle. how do i test it? the reed opens when i push on it lightly. i thought it was a one way valve so i tried breathing through it, it doesn't seem to be one way.

It is a one way valve, but isn't air tight so it won't hold pressure. Sounds like you may need to do a leakdown test to determine if it is rings or head gasket.

clean the air filter end of the tube then blow and suck ( yummy ).
You should be able to suck but not blow .
And just to be picky, the breather tube BLOWS using crank case pressure the carb does not suck from it.

bertsmobile1 said:

clean the air filter end of the tube then blow and suck ( yummy ).
You should be able to suck but not blow .
And just to be picky, the breather tube BLOWS using crank case pressure the carb does not suck from it.

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I can do both. easier to blow actually. i will go to the grasshopper store tomorrow. i am guessing that means the reed valve assembly needs replaced.

heron said:

I can do both. easier to blow actually. i will go to the grasshopper store tomorrow. i am guessing that means the reed valve assembly needs replaced.

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Yep you got it, new reed valve.
You still might be suffering from blow by or a leaking head gasket , but one thing at a time works well .

i replaced the reed valve and it helped but didn't fix it. turns out there is a 40% loss of compression in the left cylinder due to the rings and some scoring... thanks for the help!

Just my observation but the Briggs Vanguard 18hp gas V-Twin engine combined with the 718 seems to have a high percentage of engine troubles. I have seen a good number of 718's with the Briggs meet an early demise, I'm not sure if it just coincidence or that combination was just not good.

BWH, is suspect the reason behind it is. Some of the grasshoppers tend to have a lot of grass/debris thrown up in the engine area, That stuff get in and reduces the air flow that cools the engine. It was one of the major contributing factors for the problems with the Kohler Triad OHC engine on the grasshoppers and walker mowers.

ILENGINE said:

BWH, is suspect the reason behind it is. Some of the grasshoppers tend to have a lot of grass/debris thrown up in the engine area, That stuff get in and reduces the air flow that cools the engine. It was one of the major contributing factors for the problems with the Kohler Triad OHC engine on the grasshoppers and walker mowers.

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Your absolutely right! I have seen that in a number of mowers block off the fins and it will scorch the cylinder.

I am still somewhat leery of the 718 with the Briggs I've seen head gaskets as well give up, but again your theory of lack of maintenance is probably a good one.

I ran a Briggs 14hp V-Twin for over 1200 hours and it was still a great running machine when I sold it, Maintenance! Maintenance! Maintenance!