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Hello,

Since a few weaks i am busy to revise a old lawn mower (1993).
A few weaks ago i cleaned the engine (cyllinder, carburettor, bougie, flywheel, air inlet, oil) and started it, this ran fine at that time.
Now a few days ago i saw oil leaking from the gasket at the cyllinder.
I openend the cyllinder today and i discovered half the cyllinder was filled with oil.
I also noticed a screeching sound from somewhere around the crankshaft, this was not there when i started it.
I have not done anything weird with the engine it just laid on the ground.
The engine is a 4 stroke one cyllinder 12.5 hp briggs and statton and the model number is: 288707.
Does someone know how to fix this?

Berend

The only place oil like that can come from is pass the piston rings. Crankcase over full, gas in crankcase, you laid the engine on its side, piston rings or cylinder bad, crankcase vents plugged, The few things I can think of.

And the squeal that you are hearing is the starter clutch catching on the extended end of the crankshaft. Need to remove the blower housing, remove the screen and then remove the clutch. After removing clean any rust off of the end of the crankshaft, and put three drops of oil inside of the clutch area and reinstall making sure to retorque properly otherwise you will shear the flywheel key.

I notice that the inlet valve is open.
IS the port also full of oil ?
When laid on its side, carb down the crankcase oil runs through the breather then fills up the carb and flows into the engine if the inlet valve is open.

Sitting on the ground it must either be PTO shaft down or sitting on the flat back side with the spark plug pointing strait up.

Thanks for all your reactions.
To be sure i will open the crankcase to look at the pistonrings and the clutch catching.
But the answer from bertsmobile1 sounds pretty logic i saw allot of oil in the breather when i cleaned it and the motor was laying flat with the bougie faced downwards(forgot to tell it is a vertical shaft).
But the weird thing is, is that the outlet is full of oil. I dont remember if the inlet or outlet valve was open but i thought the outlet, how do you see its the inlet?

It is on the bottom.
Heat rises so most vertical engines have the inlet on the bottom & exhaust on the top.
The rate of heat transfer is directly proportional to the difference in temperatures.
So you get best cooling if the coldest air is passing over the hottest part of the engine.

Second problem is overheating of the fresh charge,
If the in coming fuel gets too hot it tends to detonate at the slightest provocation

Third problem hot air is less dense so your air fuel ratio goes towards rich when using a carb.

Fourth problem lower weight of air/fuel in the cylinder ( cause it is hotter ) so you loose power.

Fifth problem hot air fuel is easier to ignite so chances of a flash back through the carb are drastically increased particularly if the decompression is on the inlet side.

have a little think about it.
Your car runs a lot better in the cool of the early morning than it does in the heat of the afternoon.
Nearly all of the successful speed runs are done just before dawn.
While there are other factors , like the morning "still" air a big factor is the colder denser air allowing more oxygen in the cylinder.

Fuel economy tests were always done at dawn using fuel that had been allowed to "chill" overnight measured with a warmed jug to sneak that little bit extra in there.
Rigging fuel economy tests did not start with VW and end with Mitsubishi.

The exhaust valve is open not the inlet.

Okay that sounds pretty logic but i just had the chance to check it and it is indeed the outlet valve.
It also has to be because the oil was leaking from the cyllinder gasket and the outlet.
The engine now has stand horizontally the right way like on the mower for a couple of hours and no oil has come pass the piston. Is this normal then that with a little angle it leaks pass it the angle is than about 25 degree.

Hello, I’m new here, and I apologise if what I ask is covered elsewhere: I did several searches:
I own a mower with a 450 series Briggs and Stratton motor. Recently I rolled it on its side to get the blade off, but got distracted and left her on her side for half an hour or so. Now it has so much compression it won’t easily pull over (it still can however). Oil has presumably leaked into the cylinder and is causing a hydraulic lock (correct terminology??).
As suggested by other places in the web I have taken the spark plug out and get no compression. With plug out I pull started it many times in attempt to clean out barrel. It still hydraulics when plug is put back in and is hard to turn motor over. I took the fuel tank/carburetor assembly off to see if oil had leaked that way-it had as the air filter was oily.
Even with carburetor off and plug in, it did not easily turn over.
Any ideas what else I can do to get her back in action?
Thank you,
Anton

I would try A little carb&choke cleaner in the plug hole pull A bit then try blowing compressed air to clean the oil out.

Thanks Mike, help is appreciated. Unfortunately that didn't help. I have carby and muffler off, completely drained oil from sump and with plug in still too much compression. Must be another cavity somewhere that is filled with oil?? Might consider removing cylinder head (if I can find a nearby gasket set)... Thanks again.