Question concerning a flat head engine

[Matt Brandsema]

I recently made a post about my lawn mower running badly and have determined that the valves in the engine are leaking oil. (The block under the cylinder head and the face of the piston show obvious signs of leakage and oil burning.)

Topic

[Trcustoms719]

These engines do not have valve seals, the guide alone is what keeps oil from getting through (not the best design in the world).
Have you checked the compression?
Are you sure theres not to much oil in it?
And did you ever solve your fuel getting into the crankcase problem?
That is probably whats causing all your problems.

[Matt Brandsema]

My logic is that fuel from the combustion chamber is getting past the valves and into the oil supply. I checked every aspect of the fuel / carburetor system and everything checks out. The engine needs 0.5-0.65 quarts of oil and I put somewhere in between that into the engine.

So this means that there is no way to fix oil leaking into the combustion chamber than to send it to a machine shop and get the valve guides replaced?

I would check the compression but I am in Virginia and I left my compression gage back in Jersey.

[Trcustoms719]

Quoted From Xyius:

My logic is that fuel from the combustion chamber is getting past the valves and into the oil supply. I checked every aspect of the fuel / carburetor system and everything checks out. The engine needs 0.5-0.65 quarts of oil and I put somewhere in between that into the engine.

So this means that there is no way to fix oil leaking into the combustion chamber than to send it to a machine shop and get the valve guides replaced?

I would check the compression but I am in Virginia and I left my compression gage back in Jersey.

An old school small engine way to check compression is if it will blow your thumbs off the spark plug hole
when you pull the engine over it should have enough to run, but yours does run right?

This is on a push mower right?

[Matt Brandsema]

Yes this is a push mower and it does run. It runs like crap but it does run. (Low RPM and intermittent vibration) I’ll check the compression next time I get a chance using your method.

[Trcustoms719]

But an actually reading is very important.
It should have around 80-100psi.

[Matt Brandsema]

Wish I had my compression gage! Maybe I’ll rent one.. But about the valve guides, is there any way I can replace them at home? Thanks!!

[Trcustoms719]

Quoted From Xyius:

Wish I had my compression gage! Maybe I’ll rent one.. But about the valve guides, is there any way I can replace them at home? Thanks!!

You would need to have them pressed in if they are the replaceable kinda, some are not.
I honestly do not do major repairs to the smaller push mower engines most of the time
cause it’s just not worth it and
Most people will go out and buy a new mower or another engine for it instead of dropping abunch of money
in the old engine.
But that is all up to you.

[Matt Brandsema]

Thanks a lot for your help! I think I will just junk the mower, I really don’t want to go through all that trouble on this little mower. I’m marking this post as answered 🙂

[outdoorsman310]

maybe you could find a mower with a trashed deck and swap out the engines. i don’t think there is a way to change those valve guides. just make sure the crank isnt bent if you buy a used mower.

[Trcustoms719]

+1 on outdoorsman post, Just find a good used engine if your deck is fine.

[Author]

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