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Discussion Starter #1
:trink39: hi all, im looking for sum help on a 12 hp brigs motor i just got. 1st of all the motor runs great, no smoking or rough runing. that being said the problem im having is oil is coming outa of the tube that comes from what looks kinda like a pvc valve to the air cleaner. i use to have a 8hp that did the same thing, a friend told me i needed a valve job. is this the case or is there another simple fix for this? i dont know if its a pvc valve or not for sure but you can take it off and inside you can see the valve stems. thanks for any help
 

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Unless the oil is overfilled or the engine operated on a steep angle, I would suspect blowby. If it is blowby, worn rings or stuck rings would be the usual culprits, other symptoms would be oil consumption, oil on plug, or frequently fouled plug. I personally have not had a valve issue cause oil to be pushed out the pcv, but I can't say that I have seen it all. Good luck.
 

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Unless the oil is overfilled or the engine operated on a steep angle, I would suspect blowby. If it is blowby, worn rings or stuck rings would be the usual culprits, other symptoms would be oil consumption, oil on plug, or frequently fouled plug. I personally have not had a valve issue cause oil to be pushed out the pcv, but I can't say that I have seen it all. Good luck.
:ditto:
I suspect steep angle such as mowing roadside slopes.
 

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Discussion Starter #4
thanks bryan for your reply. Sounds like i need new rings. Because its not overfilled or being operated on a steep incline. :thanku:
 

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thanks bryan for your reply. Sounds like i need new rings. Because its not overfilled or being operated on a steep incline. :thanku:
How's the compression?
 

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Discussion Starter #6
I dont have a commpression tester, but it seems ok. Motor runs strong even after an hour of use. The spark plug is not showing oil on it. Thanks for any help.
 

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Is it using much oil?If not I wouldn't worry about it,a little oil in the air cleaner doesn't hurt anything.That's why they run that tube from the breather into the air cleaner,to burn the oil and vapors that would go into the atmosphere if it didn't go back ino the engine.If your using some oil,then it may be time for rings.
 

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I have some horizontal 6 & 7 hp Tecumseh's that blow oil out of the breather tube onto the tractor,and its annoying,but I cant blame the rings ,or the breather ,both have been replaced,the compression is excellent,and the breather has been cleaned thouroughly and I also swapped one off a similar engine with no change..and they did not do this before they were stored away for a few years in a dry shed too..

Only thing I can find "wrong" is one has a oil seal on the flywheel side you can hear air hiss out of when you spin it over by hand slowly--it doesn't leak any oil there however..
I'm thinking enough air leaks by that seal,to disturb the breather's reed flapper valve's action,enough to defeat it from working properly??..another small engine guru I know said the valve clearences being out of spec can aggravate this trouble too,but how,eludes ME!..
 

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I would not rebuild until I checked a few other things, if the plug is clean, blowby may not be the issue. Might be simple as a defective PCV, it should allow air out, but the reed valve should not allow it back into the engine.

As for the compression, B&S has refused for many years to publish compression data in their service manuals, unless they started recently. The standard they recomended was to rotate the flywheel backwards against the compression stroke, if it bounced back it has enough to run. Valve stem clearence being a far more common loss of compression and power than rings/cylinder wear in these motors. B&S does not consider an engine to be using excessive oil unless in burns more than 4 oz/hour.

If the engine is running well and the oil in the breather is not enough to cause the plug to foul or engine to miss, I would ignore that in favor of watching for more serious indications like oil consumtion, or quickly fouled plugs.
 

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My Briggs flatheads all have a little valve cover over the valve springs which has a little one way diaphragm in it. They can get plugged with sludge/dirrt over time. I clean them with hot soapy water then blow them out. They should permit vapor to exit the engine but not enter the engine.
 

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Discussion Starter #12
thanks for all the info on this. i ran it today mowen grass for at least an hour and it ran well, for now i just ran a hose down under frame so the oil didnt get all over side of motor and pluged the hole in air cleaner box. i checked oil after i mowed and it wasnt hardly changed on dip stick. guess i will just run it and keep a close eye on it. thanks again
 

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Is this an OHV or L head engine. I was recently given a 12hp OHV Briggs because it was blowing oil. PO thought it was shot because of the oil issue. Turns out it was a bad head gasket causing the problem. It had good compression and ran good but just blew oil. Replaced the head gasket and problem went away.
 

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Yeh I was on a Briggs site the other day trying to figure out the same problem & thats what B&S themselves say is could be a bad head gasket .
 

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Discussion Starter #15
ok, thanks i will try that. that be great if that cured the oil problem. thanks guys:thanku:
 
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