Surging B&S

550Doug · Jul 12, 2021

My 12 hp B&S motor on a rider mower has started surging, I can adjust the needle and it levels out, for a minute or two, then again starts surging. Is there a piece of dirt somewhere in the carb? Are there other reasons for a motor surging?

old · Jul 12, 2021

Could be caused by a weal spring in the linkage or something in he carb or lack of gas flow to the carb.

UncleTom · Jul 12, 2021

Sounds to me like the main jet needle has junk in it.

Rgr33 · Jul 12, 2021

Searching for fuel

Carb needs a thorough cleaning

Old Ford Mechanic · Jul 12, 2021

Common sign of a dirty carb with clogged jet passage. Disassemble and clean with spray carb cleaner. Take a
fine wire or torch cleaner and push through all passages to get the dirt out. Remove the jets and clean. Then
check the tank and fuel for water and dirt.

Steve@Advance · Jul 12, 2021

If a partial choke levels it out, it's too lean.

Common problem, they jet them from the factory right on the edge for emission purposes.

Dried ethanol attaches itself to the inside of the jet making it too lean to run. Scrape the jet out thoroughly, use a torch tip cleaner, a stiff wire, something to get down to the bare metal. Spraying and blowing alone won't get it clean.

ss55 · Jul 12, 2021

A temporary fix that sometimes works to finish the day is to turn the load needle to bottom out (count the turns as you go) and then back it out to the original setting. Sometimes that will crush or push away the dirt that is restricting fuel flow. Even when this does work, still make plans to clean the carburetor and filters very soon.

Geo-TH,In · Jul 12, 2021

Carb issue.
Take it apart, blow out jets.
Sometimes you may find after market carbs
on line.
I bought a carb for generator less than
$15. It came with adjustable jets too.
Surging is sometime an indication your idle circuit is blocked. Small jets choked with dirt, next to impossible to clean.

Determined · Jul 12, 2021

(quoted from post at 11:48:54 07/12/21) My 12 hp B&S motor on a rider mower has started surging, I can adjust the needle and it levels out, for a minute or two, then again starts surging. Is there a piece of dirt somewhere in the carb? Are there other reasons for a motor surging?

Being that you have been able to adjust the problem out at least temporarily I would agree with the other replies that say you are due for a good cleaning.

If you have done many carb's in the past then you know what to do.

If you are not at home with the inside of a carb then now is the time to pay close attention to the advise given.

Every single jet, tube ,passage needs to be mechanically cleaned out or you will be back on here tomorrow asking about other causes for why it is running poor.

If you put your mind to it it shouldn't take you much more than an hour to dig through your shop to find some tip cleaners or a guitar string or a bristle off a wire brush or a strand from a bicycle cable, throttle cable brake cable etc that will properly fit and clean everything out right the first time.

rusty6 · Jul 12, 2021

I don't know how old your Briggs engine is but if its like my John Deere with the 11 hp Briggs from the 1980s, the carb was just worn out. The throttle shaft was bouncing around in the housing all the time. We found a good used carb off a Cub Cadet and installed that. It runs good as new now. It was in one of my recent videos.

flembo · Jul 13, 2021

Before I did anything drastic I would give it a healthy drink of Seafoam and run for a while. The B&S 5hp on my wood splitter did that I had to run the choke half way to finish splitting. There are no adjustments on this carb so I tried the Seafoam, not realy expecting much but after running a few hours on half choke it straightened out and has been running great since, that was about 5 or 6 years ago. BTW I posted here at that time with the problem and was given the Sea foam tip by several folks as well as a few folks saying the engine was junk and needed replacing.

Janicholson · Jul 13, 2021

If you put effort into the cleaning process and no joy, purchase a set of number drills. Put drills through the main jet untill you find that the next
larger won't pass through. use a pin vice to hand turn the bit enlarging the hole a tiny amount. Jim

Texasmark · Jul 14, 2021

I started using SF about 2004 when I joined a boating forum and first heard about it...boaters raved about it. One day I had nothing to do and thought I had several old engines that were past their prime...weed eater, chain saw and BS lawnmower. Revived all 3 with SF. It's light mineral oil....for lube in 2 stroke engines, alcohol to dry up moisture in the fuel and also helps hygiene, and Naptha for hygiene.

Surging B&S

550Doug

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old

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UncleTom

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Rgr33

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Old Ford Mechanic

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Steve@Advance

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ss55

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Geo-TH,In

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Determined

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rusty6

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flembo

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Janicholson

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Texasmark

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