# Briggs & Stratton surging - VIDEO



## ThePixelMines

Here's the address to the video: Briggs & Stratton surging.

Model: 10A902
Type: 2189-B3
Code: 00091254​I recently changed the spark plug, cleaned the air filter, and changed the oil (dumped out the old stuff and replaced it). I ended up putting too much in. This surging problem caused me to realize that. I immediately dumped out the extra oil and got it back to the right amount. The surging continued. I just got done taking the gas tank and carburetor off and making sure both were clean.

The spark plug was very blackened so I cleaned that up, also. The surging is still happening.

Any suggestions?

The most complete diagram (as a PDF) of the engine is here.


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## geogrubb

You need to install a new diaphram kit, it is Briggs part # 795083 or old # 495770 also Lowe's has a kit #5083 which has the same parts.

Here we go;
Remove air cleaner, there are 2 bolts that hold things together, one on the front of the tank 3/8" and one into the block 1/2", remove these bolts, now "slowly" slide the carb/tank off the intake tube and breather tube, now tilt the tank in to release the throttle linkage and waalaa the carb/tank is removed. Check the intake tube to see if the “O” ring seal and plastic retainer are still on the intake tube, if so remove them and re-install them into the carb. Remove the 5 screws from the carb/tank remove carb(don't loose the spring) now spray all holes, cracks and crevases in both the carb and tank surface with brake parts cleaner, remove the main screen(looks like a thimble) with a small screwdriver pry out the main jet(carefully) and clean it, reinstall the jet, it can be difficult some times to get it to snap back in place(I use the rounded end of a screwdriver handle). Remove and clean the fuel pickup stem. Clean any junk/rust from the tank. Install the diaphram on the tank then the gasket(no goo or sealer) now carefully replace the carb(the spring will try to misalign the diaphram), tighten all screws a little at a time so as not to crimp the diaphram until they are all tight. Install the carb/tank in reverse order and you are done. If I missed something one of the real mechanics will correct me. Have a good one. Geo


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## Djz020

great work geo!! you are very good! but one thing i would like to mention, you should not spray carb cleaner and/or break cleaner inside carbs, it attracts dust and other harmful particles. We are now taught these days in school to only spray them with short blasts with high-power air guns. if you do not have those at home, i would suggest a really good,almost immaculate wipedown, some blowing with your breath,and your good.


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## ThePixelMines

*The diaphragm goes where?*

I'm a little confused. This diaphragm is not OEM, right? I found the gasket between the carb and tank, but no diaphragm.

Could you please explain to me what's wrong and why a diaphragm is my solution? I want to understand the process as well as the solution.

Thanks for your reply (both of you), BTW.


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## 30yearTech

Djz020 said:


> great work geo!! you are very good! but one thing i would like to mention, you should not spray carb cleaner and/or break cleaner inside carbs, it attracts dust and other harmful particles. We are now taught these days in school to only spray them with short blasts with high-power air guns. if you do not have those at home, i would suggest a really good,almost immaculate wipedown, some blowing with your breath,and your good.


There is absolutely no problem spraying with carburetor cleaner and or brake cleaner, unless you leave the carburetor apart after cleaning you will not have any issues with dust (or other harmful particles??). If you have compressed air it's always good to follow up, by blowing out the carburetor to insure all the passage ways are clear. Brake cleaner leaves no residue and many prefer using it over carburetor cleaner. I use both and have never had any issues.
You will never get any old fuel residue, gum or varnish off, unless you have some super kind of "Monster Breath" when you blow on it. Good luck cleaning a carburetor that way....


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## 30yearTech

ThePixelMines said:


> I'm a little confused. This diaphragm is not OEM, right? I found the gasket between the carb and tank, but no diaphragm.
> 
> Could you please explain to me what's wrong and why a diaphragm is my solution? I want to understand the process as well as the solution.
> 
> Thanks for your reply (both of you), BTW.


You may be mistaking the diaphragm for the gasket, it's two seperate pieces and many times the gasket will be stuck to the diaphragm when the carburetor is removed from the tank. When you purchase a new new one you will see, I don't think you could get the engine to run at all without the diaphragm in place.

The reason the engine surges like this, is because the diaphragm gets distorted and leaks around the vacuum port that operates the fuel pump portion of this type of carburetor set up. The fuel leaks into the port by passing the metering circuit of the carburetor. This causes the engine to run "rich" the richer fuel mix causes the engine to slow down, spit and sputter, this also causes excess carbon build up from unburned fuel and turns your spark plug black and makes the sooty discharge that you can see on your muffler.


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## geogrubb

30yearTech said:


> There is absolutely no problem spraying with carburetor cleaner and or brake cleaner, unless you leave the carburetor apart after cleaning you will not have any issues with dust (or other harmful particles??). If you have compressed air it's always good to follow up, by blowing out the carburetor to insure all the passage ways are clear. Brake fluid leaves no residue and many prefer using it over carburetor cleaner. I use both and have never had any issues.
> You will never get any old fuel residue, gum or varnish off, unless you have some super kind of "Monster Breath" when you blow on it. Good luck cleaning a carburetor that way....


Thanks 30year. Have a good one.Geo


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## ThePixelMines

*Diaphragm vs. Gasket*



30yearTech said:


> You may be mistaking the diaphragm for the gasket, it's two seperate pieces and many times the gasket will be stuck to the diaphragm when the carburetor is removed from the tank.


Okay, I have definitely confused the diaphragm with the gasket. This covered a spring. As for the gasket, they _must _be stuck together because it sure looked like one piece. The Lowe's in my area does not have this part so I'm ordering it online. I will post my progress.

Everyone, thanks for the help thus far.


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## ThePixelMines

*Success!*

The offending part was indeed the diaphragm and gasket. I ordered the diaphragm kit from Cameron Small Engines last week and just installed it moments ago. My mower is spinning like a top now.

I huge thanks to geogrubb for the solution. Also, thank you geogrubb for your instructions on removing the gas tank and carb at the same time. That made the second removal go very quickly.

Thank you to everyone else who put in their two cents. I'm thrilled to have solved the problem for under $5. I would have paid a lot more to take it to a shop.

Mission Accomplished!


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## geogrubb

Success is a wonderful sound, that's why we are here. Have a good one. Geo


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## bullmoose

I was wondering what would cause the B&S 5 hp to 8hp engines to surge?
would it be a port in the carb or flow problems caused by bad fill valve

I have seen surging problems on 18 hp lawn tractor engines also. please someone tell me what kind of goodies to soak or blow out of the carbs


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## geogrubb

bullmoose said:


> I was wondering what would cause the B&S 5 hp to 8hp engines to surge?
> would it be a port in the carb or flow problems caused by bad fill valve
> 
> I have seen surging problems on 18 hp lawn tractor engines also. please someone tell me what kind of goodies to soak or blow out of the carbs


There are several different carb setups for 5-8 hp engines, some have diaphragms some have bowls, those with diaphragms you must replace it, those with bowls can have several problems, first with it running spray/dribble carb/brake parts cleaner behind the carb and along the mating surfaces of the intake tube, if the engine tempo changes you have an air leak and need to replace the gaskets. On a lot of the engines the bowl nut is the main jet and may be clogged, there is a hole across the bottom and one down through the center, some times you can clean it and get lucky. Check the pic below for reference. Have a good one. Geo


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## 30yearTech

Many of the carburetors used on the larger Briggs engines have an idle or low speed circuit in them. A restriction in this circuit will cause quite a bit of surging while running under no load, but will go away when a good load is applied to the engine and fuel is metered through the main jet. 

Depending on what the carburetor is constructed of, will determine how best to proceed with cleaning. I typically use spray type carburetor and or brake parts cleaner. On a very dirty carburetor, I will use an ultrasonic cleaner.


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