Small Engines (Lawn Mowers, etc.): Oil in Carb, head gasket, breather valve

Question
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Followup To
Question -
I recently did a tune up of my B&S 3.5 classic lawnmower.I took the carb off to clean all the gunk that had accumulated inside. Since then the engine is blowing alot of blue smoke.I checked the carb and it is filled with oil. Now i have check the oil level and it is not too high. I do notice however that there is oil leaking at the gasket by the sparkplug. Is this the cause or is it irrelevant. I would appreciate any help you can give me
Answer -
It sounds like the head gasket by be leaking, if that's where you see oil.

The only way oil can enter the carb is either through the intake valve or the valve breather depending on the carburetor.

Do you have a pulsa-jet carb?  You will have a diaphragm between the carb/tank assembley and there will be a small round metal tube, sort of connected to the carburetor via a rubber nipple part.

Let me know what you have.
Eric

Hi i do belieave it is the pulsa-jet. The oil is comming up from the breather valve into the carb. When I took the carb off the tank i used the old diaphagm putting it back together. The carb is all plastic, and there is a long plastic tube that fits into the gas tank and also a 1 inch protrusion that has a screen over top .  

Answer
Did you tip the mower on it's side while doing a tune-up?
This is pretty common.

Anyhow, I would check and clean the valve breather.  When tipped on it's side, oil will fill the valve breather which can run through the tube into the carburetor.  The breather is a rectanglular part held in place by 2 screws.  Depending on your muffler, it may have to be removed to get to the valve breather.  You can use parts solvent or even some spray carburetor cleaner to clean the valve breather.  The valve breather should rattle like a baby rattle when you shake it...this indicates the valve is not sticking.

Let me know what you find.
Eric