Cylinder head full of gas. 11hp OHV Biriggs

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  #1  
Old 10-02-14, 09:44 PM
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Cylinder head full of gas. 11hp OHV Biriggs

Ok, I don't know much. But I know that a bad needle and seat will let gas get in the oil. But here's my story. I check the oil, it's looks fine. Crank the mower. It runs perfect for maybe 15 mins under load. Suddenly it starts running rough under load. Then quits. I try to start. No dice. I start checking for things. Pull the fuel line after the filter. Plenty of gas coming thru. Starter is bad so use the pull start. After a few pulls it cranks but runs weak under load. This goes on for maybe 5 mins. Then it starts running like new again. I think cool. I guess there was a little trash in the carb.

Then, after maybe 15 mins running great. It starts the same old won't run under load thing. Like it's starving for fuel. I know I'm getting real low on gas. I shut it down. Run to the store for gas. Maybe 10 mins. I pour in about a gallon. I pull the mower to crank. And it's locked up. After checking what I know to check. I pull the plug just to see if it will turn over. Before i get the plug completely out. Gas comes gushing out the cylinder head. I say 1/2 pint at least.

So my question for now. Can gas get in the oil while the engine is running? If so what would cause that? Again. This a 2007 11HP Briggs on a Snapper rear engine rider.

Edited to add. That even when the cylinder was full of gas. The dip stick was showing only a little above full. Till this mower, I've always ran flat heads and would never know I had gas in the oil unless the dip stick showed over full and the oil was diluted.

Sorry for the long ramble. You guys take me to school. That's why I joined here.

Thanks in advance.

IH
 

Last edited by ih4630; 10-02-14 at 10:08 PM.
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  #2  
Old 10-03-14, 05:38 AM
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Yes, gas can get in the oil while the engine is running. It's particularly bad because it's flowing past the piston and washing the oil off the cylinder walls. The float and needle valve in the carburetor is usually the culprit.
 
  #3  
Old 10-03-14, 08:57 AM
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Thanks Dane. I'll change out the float and needle. But I'm still curious why the engine would run like it's starving for fuel when apparently it was getting flooded. An engine that's getting too much fuel or flooding should smoke and have a strong odor of un- burned fuel. Yet there was no smoke, just a big loss of power. Before I shut it down. It pulled like a diesel engine when the fuel filters are clogged.
 
  #4  
Old 10-03-14, 09:17 AM
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I generally don't think of a rich running engine as visibly smoking much. Coolant and oil make smoke that's easier to spot but sometimes fuel doesn't. Did you pull the spark plug to see what it looked like?
 
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