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Hello everyone,

I have a Briggs and Stratton 155 Series 4 that I took out for the spring. It’s about 5 or 6 years old. I have cut a 2 acre lawn 3 times with it this year. I cut the lawn yesterday and stopped the mower. It was working fine.

When I came back from lunch, I smelled fuel. Fortunately, I didn’t start the engine. It was parked level and when I checked, there was fuel running off the riding mower deck and fuel in the oil. I have added a photo. As you can see, the carb is really wet with fuel and it was dripping pretty good from the mower deck.

I am guessing this is some type of carburetor issue?

Carb needle and seat need cleaned or replaced.

Also get a cheap inline fuel shutoff valve and use it.

Appears that the Op has a 15.5 hp 310000 series engine with a Nikki carburetor. IF so then the carburetor bowl gasket has probably failed around the inlet tube. Two different bowl gaskets were used so the model, type, and date code are need to get the correct gasket.

It would be one these two gaskets. I suspect it is the one on the right as that is the one gives me the most problems.

slomo said:

Also get a cheap inline fuel shutoff valve and use it.

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Will not resolve an actual problem of a defective gasket. Just gives a false sense that nothing is wrong and just masks the real problem.

Thank you very much for the replies.

I do have an inline fuel valve. I use it to shut the fuel for maintenance and also when winterizing the riding mower. It’s not shown in the photo, but it’s off to the right, just before the fuel filter. Makes it easier to change the fuel filter by simply shutting the fuel line.

I’ll pull the carb off and see which gasket it is. I’ll also check the needle and seat while I’m at it. Is there any special tool required to remove the needle seat?

I’m a bit surprised that I would have carb issues already, the mower isn’t all that old. I have a smaller mower (Tecumseh) with the original un-serviced carb that is going on 20 years old.

The Nikki carburetor don't a separate per say as the fuel transfer tube is the plastic piece which the float is attached to.

These rather expensive and don't normally need changing.

Is that the one with the jet that gets easily lost?

StarTech said:

Appears that the Op has a 15.5 hp 310000 series engine with a Nikki carburetor. IF so then the carburetor bowl gasket has probably failed around the inlet tube. Two different bowl gaskets were used so the model, type, and date code are need to get the correct gasket.

It would be one these two gaskets. I suspect it is the one on the right as that is the one gives me the most problems.
View attachment 64729View attachment 64730

Click to expand...

I hate those gaskets, i mean why. They could've used the ages old design of the run of the mill carburetor, but they had to make it "better" i guess.
I keep several of each kind on hand because they either always tear, or don't go back in right. which im sure replacing them when you remove them is the correct thing to do.

Actually I love them
Because the main jet is in plastic tube it does not corrode anywhere near as much as the ones that are brass in zinc because there is no galvanic cell .
The jet itself rarely clogs and the only problem I regularly come across is the O ring around the fuel inlet tube seems prone to failure which allows the fuel to bypass the float valve .
The silly problem is of course hitting the main jet from the wrong side with higher air pressure than you should ever use when cleaning a carb and sending it into low earth orbit
I used to think the flooding was because of the O ring around the main jet but over time I have come to realize that if it does not fall out under it's own weight when the transfer tube is inverted then it is good and the problem will be the afore mentioned inlet tube O ring

Thus the main jet stays in place , get a cleaner passed through it, no carb cleaner as carb cleaner deteriorates the O ring , new gasket and job done in 5 minutes .

bertsmobile1 said:

Actually I love them
Because the main jet is in plastic tube it does not corrode anywhere near as much as the ones that are brass in zinc because there is no galvanic cell .
The jet itself rarely clogs and the only problem I regularly come across is the O ring around the fuel inlet tube seems prone to failure which allows the fuel to bypass the float valve .
The silly problem is of course hitting the main jet from the wrong side with higher air pressure than you should ever use when cleaning a carb and sending it into low earth orbit
I used to think the flooding was because of the O ring around the main jet but over time I have come to realize that if it does not fall out under it's own weight when the transfer tube is inverted then it is good and the problem will be the afore mentioned inlet tube O ring

Thus the main jet stays in place , get a cleaner passed through it, no carb cleaner as carb cleaner deteriorates the O ring , new gasket and job done in 5 minutes .

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must be because you're upside down over there.

JohnnyCanuck, Bert's right the main jet o-ring is very problematic replace it with a Kawasaki #92055-7013 (B&S) doesn't sell them except on the main jet, you might take a close look at the float needle if it's grooved or torn replace it and bowl gasket and you should be good to go. And use non-ethanol gas.

Thank you everyone. I’ll be taking the Nikki carb apart tomorrow to see what it looks like inside. I’m in Europe, I just buy the regular 95 gasoline, which is all that is available here. Could be age related - this particular Briggs probably has between 350 and 400 hours on it, if not more. I also think the fuel shutoff solenoid may not be working. I can’t hear it clicking anymore. I’ll try testing it with a 9 volt.

Spent the day fixing a top oil seal leak and replacing the flywheel on a 15+ year old Tecumseh VLV-126. Ran it for 30 minutes and no oil! Been trying to fix this for quite a few years.

StarTech said:

Will not resolve an actual problem of a defective gasket. Just gives a false sense that nothing is wrong and just masks the real problem.

Click to expand...

But if a leak develops it keeps your garage from being flooded with gasoline.

JohnnyCanuck said:

Hello everyone,

I have a Briggs and Stratton 155 Series 4 that I took out for the spring. It’s about 5 or 6 years old. I have cut a 2 acre lawn 3 times with it this year. I cut the lawn yesterday and stopped the mower. It was working fine.

When I came back from lunch, I smelled fuel. Fortunately, I didn’t start the engine. It was parked level and when I checked, there was fuel running off the riding mower deck and fuel in the oil. I have added a photo. As you can see, the carb is really wet with fuel and it was dripping pretty good from the mower deck.

I am guessing this is some type of carburetor issue?View attachment 64727

Click to expand...

I just had same problem, I replaced fuel solenoid shut off valve. I have b&s 17.5 hp on a craftsman LT 1500, it has quite a few years on it so I replaced the Nikki carb. With aftermarket carburetor. Also put on new battery but it ran down so I am replacing regulator. I must admit this old mower has been treated roughly.

I took apart the Nikki carb. It was full of fuel and there was fuel up in the crankcase vent tubing. I also took the opportunity to drain out the engine oil. It was full of gas as evidenced by the rainbow colours that were appearing as it drained.

I got the carb apart. I tried blowing past the needle valve when it was open and closed. When open, the air would go through, when closed, no air path. I think the needle valve is working properly. I couldn’t see anything obvious, but I have attached a photo. The black rubber gasket and the circular black seal seem to not be very pliable. I did see something that looked a little suspicious and I have included a photo. Inside the circular area (is it a fuel passage?) there is some kind of fragment that looks like part of a gasket/seal, but I couldn’t locate where it came from. There seemed to be no rubber seal on the end of the emulsion tube. In fact, I couldn’t get the emulsion tube to move. It seemed really fixed in there.

Any advice (besides changing the circular black seal and the main gasket would be appreciated. I don’t want this to happen again and I need this machine in working order.

Thanks!!

The hard O ring will allow fuel to leak past the float valve
Replace it
Chek what part you order because there are 2 varieties of this seal
One has the "o-Ring" as part of the seal & the other ( latter style ) has it as a stand alone item .