Snapper 12.5 hp lawn tractor oil in breather on hard load

[mdhanners]

I have a 12.5 hp briggs 3 yrs old only used engine one summer.. which had the carb seat leaking into crankcase. I fixed that then this year. I changed the oil twice after seat repair. I watched the oil level for a few weeks no fuel leaked in level stayed the same. I installed a inline shut of from the tank let the engine run till it died choked it and crank till it was completly dry in bowel. This year when I started it blue smoke out of exhaust blows when first started then runs fine as I hit heavy grass causing a load on engine blue smoke filled the sky. engine stummbled then as load lessend engine ran fine. Hit more grass more smoke had my wife watch the exhaust as I cut (as it is a rear engine machine) She saw no smoke at all untill I pulled up out of ditch or hit heavy load then it would cloud the sky. till I lessened the load. At this point im thinking it was done. headed to my shop let it run for awhile with no smoke but oil residue was around the muffle outlet slits. Checked oil after it drained dwn It was just under the top line on cross hatches on stick (while it was screwed in) Started back up mowed nomore smoke that I could see ran fine. Next day started to pull out of garage hard to start n blue smoke filled garage. Check for fuel in oil no gas smell at all. pulled breather filter was dripping oil cleaned assy put filter in out of anothe engine in my shop.(it is very dirty and may be restsircted also) started it up no smoke mowed with no noticiable smoke. I pulled breather yesterday a it was smoking on start up again found a small amount of oil in assy. pulled the assy from carb opened shut off from tank and pressured fuel tank while watching carb throat for leaking fuel it stayed dry.let it set till this am carb thorat is dry...Yay but now I know crankcase pcv system is pushing oil into breather however with an engine with maybe 25hrs or less and as well as it runs when It dosent smoke I feel the rings valves ect are fine. So I lkeft breather assy off pulled it out of grage it started with out smoking. Let it run for 10-15 mins put finger on vent hose had some pressure as it should but no oil residue at all on my finger tryed several times thru the period it ran it was dry air venting fron case. Now guess I should go find some heavy grass to run it thru without vent hose attached and see if I get excessive blow by. But I feel the vent is working fine with out the breather assy attached. Any Ideas and have you seen a plugged air filter devlope excessive vacum pulling reed valve open in cas and sucking in oil? or anhy other senerios?

 

[KYErik]

If much raw gas got into the oil back when the carb seat was leaking and you were running the engine for many hours with lots of gas in the oil, it may have diluted the oil enough to wear out the piston rings so now you have a good deal of blowby when the engine is under load.

Does your oil get black really quickly after you change it? If so, this is a sign of lots of blowby/poorly sealing piston rings.

I had an old tired engine do what you are describing (it had so much blowby under load that it would blow oil into the air cleaner through the PCV breather tube and make smoke clouds). I just removed the breather tube from the air cleaner and sealed the hole in the air cleaner up so all air entering the carb was still filtered. It would blow out a little oil must under load, but not much. The engine still seemed to have pretty good power so I just kept running it that way and checking the oil a little more often.

Switching to a heavier weight of oil (like 20W-50) will likely help seal up the rings a little bit better.

 

[sox3]

Those breathers have a drain hole in them, make sure its clean. What weight oil are you running? Could be ring problem if used with that oil gas mix for long time. Would need to do a leakdown test to check for that. If this is an overhead valve engine, could have a head gasket starting to go. they sometimes leak between the cylinder and the pushrod chamber. That gives you oil in breather and oil burning. Just my thoughts.