Blowing oil out of breather

[Cfs]

I am helping a neighbor with a 12.5 hp Briggs vertical engine 289707 1179E-3 020503ZD. It is a single cylinder L Head design. It does not have a Nikki carb.

The engine had no oil to speak of when I first checked it. The oil sump was full of gas. I drained it out and refilled it with oil. I dropped the bowl off of the carb and cleaned the needle & seat and the float, I installed some new fuel line and a shut off valve. I had to jump it to get it started. Once it started it smoked like mad. I hoped it would stop smoking thinking the muffler had old gas and oil in it I had noticed that the air filter was saturated with oil when I had it off to clean the carb and I blew it out with my aidcompressot. The engine started to run rough so I shut it down. Checked the spark plug and cleaned it put it back in and it would not start. Remembering how the air filter looked I removed it and started and ran it with filter off. Started right up but after a few minutes it was blowing oil mist and oil out of the hose from the breather to the bottom of the air filter box. It was getting worse the longer it ran with no filter in it to catch the oil.. it started to look like Mt St Helen’s bad head gasket? Oil breather? Engine ran strong

Help?

 

[Auto Doc's]

Hello C.,

Broken rings and it needs a replacement engine. L head engines do not act the same as an OHV engine.

 

[StarTech]

20+ yr old engine.

There is one other thing that might be happening. It may be a severely worn exhaust valve guide. I have seen a lot of back pressure to cause oil to be blown out of the breather when the guide is severely worn.

The only way to know is to remove the head and check the cylinder condition. While open see how much wiggle there is with the exhaust valve. Compare this to the intake valve should be about the same normally. But first do a leak down test before removing the head this will tell you if cylinder damage too bad to go even go any further. You are looking for under 20% with no leakage past the valves. A while you at it check the valve clearances. They are probably at near zero due to the age of the engine.

But if the engine has been run a long time with gas laden oil all bets are off as anything could be bad.

Either way it is a good learning project as you can't make it much worst.

 

[Cfs]

I like your take on ‘A good learning experience’.
With this being a L head and looking at the shape of the head gasket it does not seem that a blown head gasket would cause oil blowback like a OHV engine which has a separately secured valve section of the head gasket. This is just one large ‘keyhole’ shaped configuration with no separate enclosed valve area. I can remove the head but will not be able to get to the rings without completely disassembling the engine correct

 

[Cfs]

Hello C.,

Broken rings and it needs a replacement engine. L head engines do not act the same as an OHV engine.

I looked at an IPL last night and a light bulb came on that this L Head does not have a separate valve ate of the head gasket. The valves on this style of engine are exposed to head pressure and not secured by a section of the head gasket..correct? So a blown head gasket would not cause oil blowback and oil burning like An OHV engine would.. Correct?
I am just learning and am kind of amazed that the engine could run as well as it did with the exception of all the white smoke and burning oil. Crazy!

Guess the oil is getting past the bad rings and pressurizing the crankcase forcing oil out of the breather as well as oil getting into the exhaust/muffler.

What do you recommend that I do to confirm a diagnosis. Pull the head off? Seems like there is no easy way to get to the rings without disassembling the engine. Will I be able to see anything of significance with the head off?
Spit

 

[Forest#2]

In post #3 StarTech said to do a leak down test. Very good suggestion.

Search for info on-line about doing a leak down test and the price of the tester.
HF sells a leak down tester. I bought a ORC few years ago and it's a great tool.

Leak down test allows me to check/test/analyze a new to me non running engine to see if it's worth trying to get it up and running.
If you are going to be working on engines it's just one of the best tools to have around.

 

[Cfs]

20+ yr old engine.

There is one other thing that might be happening. It may be a severely worn exhaust valve guide. I have seen a lot of back pressure to cause oil to be blown out of the breather when the guide is severely worn.

The only way to know is to remove the head and check the cylinder condition. While open see how much wiggle there is with the exhaust valve. Compare this to the intake valve should be about the same normally. But first do a leak down test before removing the head this will tell you if cylinder damage too bad to go even go any further. You are looking for under 20% with no leakage past the valves. A while you at it check the valve clearances. They are probably at near zero due to the age of the engine.

But if the engine has been run a long time with gas laden oil all bets are off as anything could be bad.

Either way it is a good learning project as you can't make it much worst.

I have a Harbor Freight Leakdown Tester. But being honest I have never mastered it. I can pull the head off and I could take the breather off to view the valves and springs. From there I can get a look at both ends of the valves and see how sloppy the guides are.
Let me know if you have any other suggestions
Thank you
Spit