Gas in push mower oil reservoir

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Hey guys,

As the topic says. I have a Troy bilt push mower that I bought on a lowes clearance about 5 years ago and has ran like a champ. Saturday I was checking the oil and noticed that it smelled a lot like gas.

I dumped the oil and sure enough it was diluted with gas. My first impulse was to check the carb and so I pulled it apart and it was completely spotless. Now I could have missed something but I highly doubt it. I dumped a fresh fill of oil in it and cut the grass. Well yesterday I checked the oil dipstick just to see if anything has changed and yet again it's diluted with gas. It has a B/S motor on it and it has been flawless since I bought it and has always had on time oil changes.

What's going on here?

My dad suggested it's just how a cheap mower is nowadays regardless of what kind of condition to keep it in but I'm not of that mindset obviously.
 
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If the mower runs fine, like it has prior to getting gas in the oil, there is only one way it can get gas in the oil, and that is when it is not running, and the carb running over and getting into the combustion chamber, and going past the rings. BUT, usually it will also run out of the carb intake, and foul the air cleaner. Also, is the oil level in the crankcase rising? OR, is it just the normal smell of the oil?
 
Carb is leaking gas while sitting.

I have had it happen a ton on riding mowers. I usually install a fuel shutoff valve.


most likely a worn needle valve in the carb..

Sometimes those carburetor are <30$ might just be worth a new carb if you arent handy with small engine carbs.
 
The air filter was clogged. I see that I failed to mention that. Also there is no smoke upon start up and it runs fine otherwise.
 
Odds are the carb is bad. I had a similar problem with a Honda engine, I rebuilt the carb and that solved the problem. You could install an inline fuel shut off valve which will help but that isn't really fixing the problem.
 
Ok guys thanks for the info I'm gonna look up the shut off valve and give that a go.
 
The needle and seat in the carburetor that shuts off the flow of gas is deteriorated or slightly blocked with some gunk. To fix it right you need to replace/rebuild the carburetor. If it runs fine and you want to be cheap, just cut the fuel line and add a $5 Briggs fuel shut off valve. Shut it off 30 seconds before you are done cutting and the remaining fuel in the bowl will be consumed. No more fuel dilution issues.
 
Had the same problem with a lady-friends mower last year. Replaced carb and installed an inline fuel cutoff. Problem solved.
 
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