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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 12592
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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My church's Poulan riding mower has an issue I cannot solve.

Customer Question

My church's Poulan riding mower has an issue I cannot solve. About every 6 weeks during the winter, I start it and let it run a few minutes. This time, it would not turn over despite a strong battery. It turned out that the cylinder had a hydraulic lock. When I removed the spark plug and turned the engine over with the starter, a pitch black liquid that looked like thin oil (but I don't think it is because the crankcase oil is fresh and NOT pitch black) pulsed out with each stroke.
I was finally able to start the engine, but it would run only on low throttle. For a few seconds, it would run fairly smoothly, the start to miss and belch blue smoke for a few seconds, the run smoothly again for a few seconds, repeating the condition. If I advanced the throttle, the engine would race momentarily, then run rough, belch thick blue smoke and quit. I was able to restart it, but the condition persisted.
Upon my first inspection when I arrived, I noticed the fuel tank was an inch down from full. When I discovered the hydraulic lock, I thought the liquid might be fuel that, due to a stuck float valve in the carburetor, siphoned from the manifold through an open intake valve into the cylinder. I eventually ruled that out. Any suggestions??
Submitted: 9 months ago.
Category: Small Engine
Expert:  Don replied 9 months ago.

Hi there my name is don i will try to help you

it sounds like you have a bad ring or there is a gouge in the cylinder wall allowing the oil to bypass the rings

i would do a compression test to see what it is and also a cylinder leak down test

you can try a wet test as well this will tell you if it is a ring or stuck valve

hope this helps you if you have any questions please came back and ask me through this post

don