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donmoore1904

Briggs 10hp 243431 intermittently stops

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donmoore1904

My motor runs great, except every so often (maybe once every two hours) while mowing light grass it just stops. When this occurs, it pretty much starts right up and runs again. Some cranking is sometimes required.

Anyone see a symptom like this or have a clue? I am leaning in the direction of fuel, maybe a speck of dirt in the carb. My small brain can't imagine a failure mechanism in the spark that would do this.

I might also mention that starting the motor cold has become a bit tricky - the throttle has to stay shut completely, and advancing it has to be done very carefully or it stalls. After a minute or two, trial advances of the throttle have to be done until apparently just the right part of the stroke is hit so it doesn't stall when advancing. Once warm it is ok, yet advancing from closed throttle can cause a stumble similar to when cold. It didn't use to exhibit this behavior, which while annoying hasn't concerned me as much as the stall under load.

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HubbardRA

I start my 243431 on choke and within a few seconds completely take it off choke. I may run it on choke for 15 to 20 seconds. Then I go directly to work with the tractor.

It sounds like you have one of a couple problems. Your carb is likely set too lean, or you have a gasket leak. You can adjust the carb. To check for a gasket leak, spray water around the gaskets with the engine running and listen for a change. If the water hits a vacuum leak, the engine will slow down, stumble, or die.

You may also have a valve that does not have enough clearance. Valves get longer as they heat up and without proper clearance can stop sealing when they get hot. I had one doing this recently, but that happened after about 20 minutes while mowing my lawn.

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Tarheel

My guess is that the fuel line or tank is blocked. Easy enough to pull the fuel line and let it drain into a clean clear plastic soda bottle. Let it drain for a bit and see if it is slow or gets slow.

Also check for water. IMO

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dentwizz

I would check the carb float/needle setting. Either sticking closed or the setting is too low of a level of reserve in the bowl. Should be level with the float and body when in the closed position and have no binds in movement. Sometimes a gum buildup on the needle can cause that sticking effect. Could also be partially restricted or plugged in the orifice from the same thing. A piece of wire will clean that when poked in the holes.

P.S. I just got a NOS rebuild kit for that carb off ebay and it was running badly. Turned out there was a dust buildup inside the emulsion tube from sitting! :o

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simple_stan

Certainly sounds like two problems. After two hours cutting, your fuel tank would be low and you may be developing a vacuum lock. I would do like Tarheel said with your fuel tank low on fuel. Then I would check the carb.

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MrSteele

2 hours before it has a problem, then starts back up?

I would check:

1. Fuel filter

2. Properly venting gas tank cap

Starting and having to slowly open the throttle

1. Too lean due to needle setting.

2.If the problem started all at once, look deeper into the carb for trash across the needle/seat, clogged emulsion tube. If the problem is trash, you need a new filter, being sure to get a proper one for gravity feed

Sounds like you have 2 problems, related to each other.

Solution is to keep a clean filter, buy gas from the same station that has never given problems before. Depending on the gas station, some of them sell dirty gas these days.

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donmoore1904

I am so sorry to just be getting back here to see your replies - are all very helpful. Several very good ideas, which I will pursue. Here is a little more info -

Since several mentioned tank venting - my fuel gauge plastic fell off a year ago. I have to admit I did nothing about it, and fuel sputters out of the hole if the tank is too high - so I keep it low. Hmm, tank venting. Am I sucking dirt into the tank (stupid question?)?

I rebuilt the carb two years ago, and I never got it just right. Initially, the carb leaked fuel occasionally, which I was told was not having that diagonally installed internal part (long tubular piece a jet threads into) seated right. The one where you use a screwdriver down inside the body to install/remove. The threads didn't seem right and I didn't want to force it, as I recall. But the carb stopped leaking gas at some point. The lean behavior showed up later, and as you can see I am not a carb "tinkerer" and haven't addressed anything until the sky may now be about to fall in. I'm an electrical guy. I might have even taken it to the stealer to look at, but he is not much better than I (!).

Thanks again for the great suggestions of things to do/look for.

ps I am going out directly to try to tweak the carb. Snow expected tomorrow, and it's a bit windy and cold. Sun is shining right now though!

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donmoore1904

I did some adjusting and found that when I got the smooth acceleration from idle, it was hard to obtain smooth acceleration at the midpoint of the throttle. In other words, smooth acceleration from idle to midpoint, stumbling, then recovery to full throttle. I obtained a compromise to almost fully eliminate the latter, and keep smooth acceleration from idle.

I recall a similar symptom when I rebuilt the carb.

Edit - I just reviewed Zippo's youtube on tuning a cast iron Briggs. I think I need to go re-seat the needle valve or jet as a first step, and then just tinker with the adjustments.

If I can't get it perfect, at least making it start easier would be a plus. There is nothing worse than babying the throttle at a very low idle in 10 degree weather, restarting over and over, until it gets warm enough to run at speed. This carb adjusting isn't for wimps!

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MrSteele

Keep at it. This carb adjusting is indeed for anyone who wants to do it. Looking for wimp problems, play with 2-cycle carbs, those are far more interesting to adjust. Simply breathing at the wrong time, making your hand jerk sets it the wrong way.

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donmoore1904

Update -

After tuning, the engine changed to starting without being finicky, and the choke could be removed after 20 seconds like normal. Worked fine plowing at maybe 1/3 to 1/2 throttle.

Then I did run into missing, when I was plowing uphill and changed to 1/2 to 5/8 throttle (I usually don't run it that fast). I leaned forward while in motion and tweaked the needle, and was able to smooth it out. Still seems kinda touchy and one thing throws the other off - maybe that is how they are and I just need to put more effort in.

The mowing stall I reported in this thread, either due to tuning and/or because the ambient is now cold, appears to have changed to an abrupt decrease to idle, regardless of throttle position. Or maybe that was some icing as I also have had, but it goes back to the set speed after only 5-10 seconds. Seems more similar to the behavior reported in this thread. Hopefully I can make it to warmer weather to check into that.

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