B&S Engine Stalling

I have a lawn mower (which I found on the curb) that runs OK for a few minutes sometimes longer, but inevitably stalls, needs to be re- primed, and re-started. (But will restart with no wait.) When it dies, and I go to re-prime it, you can hear and feel that the primer bulb sucking air at first, turning to a more reasonable fuel sucking sound/ feel at times (or after a few tries).
When I got it I replaced the spark plug, changed out the oil twice, cleaned out the carb, replaced the fuel line, replaced the needle valve and a badly deteriorated seat, and put the thing back together. There seemed to have been some water in the engine, as the first change of oil was very cloudy. It is a 4.5 hp Briggs and Stratton 12H800, in a Murray 204210X8B.
Not sure where the primer is pulling air from, why it is stalling, or how to fix the issue (cheaply). Any suggestions would be greatly appreciated.
Thanks.
Jerry
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check the air equalisation hole in the fuel cap and the float valve

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Lossen the gas cap a couple turns, and see if the problem goes away. If so, the vent on the gas cap is not working right.
Bob
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On Mon, 03 Sep 2007 19:12:28 -0700, snipped-for-privacy@gmail.com wrote:

Are you sure there is no crud in the tank blocking the pickup.
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On 9/5/2007 8:02 AM, snipped-for-privacy@gmail.com wrote:

Have you replaced the primer bulb/fuel lines? The kit usually has both the bulb and lines. About $7 @ Lowes.
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Ted
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I've worked on a lot of lawn mowers, but this one has me scratching my head. Since it starts right back up, that rules out valve clearance, and bad ignition coil.
Makes me wonder about water in the gas, or bad gaskets as you say. Always a good idea to pull the motor cover off, and clean off any grease, grass, or dust from the top of the motor. Air cooled, you know.
If the primer is sucking air, makes me wonder if the vents in the gas cap are clogged? Or, if the fuel line from the tank to the carb has a problem.
Try running the mower with the gas cap loose half a turn or so. The more I'm thinking, the more it sounds like a clogged gas cap vent. Needs to draw air in, to replace the gasoline that is going out.
--
.
Christopher A. Young
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On Wed, 05 Sep 2007 13:02:06 -0000, snipped-for-privacy@gmail.com wrote:

Some "tiny holes" need to be cleaned with a piece of wire. A wire plucked from a wire brush (stainless is best). These ports clog and you don't get the right air/fuel mixture in the carb throat.

Have you tried to run this engine without an air filter after it stalls? Pull the air filter off, run it and see if it stalls.
Before it dies out, can you spray carb fluid in to keep it running?
-- Oren
"The voices in my head may not be real, but they have some good ideas!"
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Muffler may be clogged. Engine needs to breath just like a human, inhale and EXHALE! Check your muffler for free air flow.
Cheers, Joe
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I've heard of this, but never had it happen too me.
Maybe an air/fuel mixture screw adjustment would help the OP.
-- Oren
"The voices in my head may not be real, but they have some good ideas!"
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