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#1
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Mower engine problem
I have a 3.5 hp B&S "classic" engine. While mowing, it started sputtering
and surging like it was about to run out of gas but it has plenty. It does this in any throttle position. I took off the carb and cleaned the strainer. It had some junk, but wasn't very dirty. After I put the carb back on, it ran fine for 3 minutes then started surging again. One thing I noticed is that it will run smooth seconds before it runs out of gas. Sounds like a carb problem, but I'm not sure. Thanks for any help. John |
#2
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JohnR66 wrote:
I have a 3.5 hp B&S "classic" engine. While mowing, it started sputtering and surging like it was about to run out of gas but it has plenty. It does this in any throttle position. I took off the carb and cleaned the strainer. It had some junk, but wasn't very dirty. After I put the carb back on, it ran fine for 3 minutes then started surging again. One thing I noticed is that it will run smooth seconds before it runs out of gas. Sounds like a carb problem, but I'm not sure. Thanks for any help. John You didn't mention checking the air cleaner. Did you? If not, maybe it's gunked up and "choking" the engine? Try running it for a bit with the air cleaner removed. Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) "Truth exists; only falsehood has to be invented." |
#3
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Sounds to me like the gas cap isn't vented correctly either the holes are
plugged or you replaced the cap with a non vented cap. What happens is everything is fine for a few minutes then the engine quits you wait five minutes (the vacuum in the tank has equalized by then) and then it will run fine for a few minutes then repeat. Try unscrewing the cap a little so that it doesn't pull a vacuum on the tank to eliminate this as a possible cause. Good luck, Rich "JohnR66" wrote in message ... I have a 3.5 hp B&S "classic" engine. While mowing, it started sputtering and surging like it was about to run out of gas but it has plenty. It does this in any throttle position. I took off the carb and cleaned the strainer. It had some junk, but wasn't very dirty. After I put the carb back on, it ran fine for 3 minutes then started surging again. One thing I noticed is that it will run smooth seconds before it runs out of gas. Sounds like a carb problem, but I'm not sure. Thanks for any help. John |
#4
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"Rich" wrote in message g.com... Sounds to me like the gas cap isn't vented correctly either the holes are plugged or you replaced the cap with a non vented cap. What happens is everything is fine for a few minutes then the engine quits you wait five minutes (the vacuum in the tank has equalized by then) and then it will run fine for a few minutes then repeat. Try unscrewing the cap a little so that it doesn't pull a vacuum on the tank to eliminate this as a possible cause. It could be the cap vent is stopped up. Last year a fellow at work had a mower that would run for a short time and quit and repeat. I told him to check the cap. He found he had swapped the cap from the can he filled the mower with the one on the mower tank.. The filling can lid was not vented so it gave the same effect as you describe. |
#5
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"JohnR66" wrote in message
... I have a 3.5 hp B&S "classic" engine. While mowing, it started sputtering and surging like it was about to run out of gas but it has plenty. It does this in any throttle position. I took off the carb and cleaned the strainer. It had some junk, but wasn't very dirty. After I put the carb back on, it ran fine for 3 minutes then started surging again. One thing I noticed is that it will run smooth seconds before it runs out of gas. Sounds like a carb problem, but I'm not sure. Thanks for any help. John Thanks for the replies so far. I failed to mention that I ran it with the air cleaner off and had the same result. After reading the posts about the gas cap, I checked and can see that the holes are not plugged. I should mention that the carburator is the type with the priming bulb. The carburator appears to be molded out of nylon plastic and bolts to the gas tank with 5 screws. John |
#6
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the rubber gasket between the carb and the tank is called a diaphram.
it pumps fuel up to the carb, try putting in a new diaphram and that should fix it. if your primer bulb is the least bit deteriorated replace it also. ..... in some cases, the tube that the carb slides onto gets loose or blows the gasket where it attaches to the engine block, that little gasket cost little but can cause problems if bad... also snug up the head bolts,the ones by the ex tend to loosen... good preventative maintenance is to take off the sheetmetal and clean the grass out of the cooling fins, this is a good time to check the intake tube and gasket... lucas |
#7
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forgot to say, change the air filter. i dont think your carb is
designed to work with the air filter bolt out. lucas |
#8
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On Tue, 31 May 2005 22:52:42 GMT, "JohnR66" wrote:
I have a 3.5 hp B&S "classic" engine. While mowing, it started sputtering and surging like it was about to run out of gas but it has plenty. It does this in any throttle position. I took off the carb and cleaned the strainer. It had some junk, but wasn't very dirty. After I put the carb back on, it ran fine for 3 minutes then started surging again. One thing I noticed is that it will run smooth seconds before it runs out of gas. Sounds like a carb problem, but I'm not sure. Thanks for any help. John Although there are other possibilities, you might also check to see if the head gasket is leaking. I had a mower with similar problems and when I happened t o pass my hand past the side of the engine I felt this hot blast coming from the gasket. Replaced it and the engine worked fine. Gary Dyrkacz Radio Control Aircraft/Paintball Physics/Paintball for 40+ http://home.comcast.net/~dyrgcmn/ |
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