# Yard Machine B&S 4HP Mower terrible idling??



## walkman (Nov 8, 2009)

The mower will start fine, but it sputters and barely keeps running. The way the mower is tilted (up or to the side) affects how well it idles.

I changed and gapped the plug, and cleaned the air filter but it made no difference. I also sprayed some engine cleaner fluid into the air inlet which made the engine run better for only a minute. 


I'm thinking the next step is to rebuild the carb -- but are there other steps I should try first?


B&S: 10A902 2189 B3 -- 9000 Series (I think)


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## 30yearTech (Sep 14, 2006)

Sounds like you have a leaking carburetor diaphragm. 

I am sure geo will be along and post his instructions on how to replace the diaphragm along with the part numbers.

If he doesn't then I will find a copy and post here for you... :thumbsup::thumbsup:


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## geogrubb (Jul 28, 2006)

Thanks 30Year, making me do all the work.lol

walkman;
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), now with a small screwdriver pry out the main jet(carefully) and clean it, check the “O” ring on the main jet for damage, if it is damaged it must be replaced, 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(not necessary if the fuel tank was clean). 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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## walkman (Nov 8, 2009)

Thanks for your help guys.

Is the diaphragm kit merely a couple of gaskets? In which case, I'm guessing that you think the problem is junk or corrosion restricting air/fuel flow.

Is there a part in this style carb that might actually be broken?


Finally, if Lowes doesn't carry that part any more do you know of a place in Atlanta that sells small engine replacement parts?


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## geogrubb (Jul 28, 2006)

The kit amounts to a diaphram, gasket and usually a spring and a mesh filter, sometimes just the diaphram and gasket, sells for about $3-4. The diaphram looses its flexibility and quits pumping properly. It's a very simple carb, nothing will be broken. I am in St. Louis so I don't know what is available there, any non-bigbox equipment dealer will have the kit, I mention Lowe's as they are the only bigbox store in my area that carries it. Take your time and follow the instructions step by step and you will be going in no time. Have a good one. Geo


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## Lawnmowertech (Nov 12, 2008)

geogrubb said:


> Thanks 30Year, making me do all the work.lol
> 
> walkman;
> 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.
> ...


lol better you than me lol just kidding
besides if he cannot find that part locally he can look on my website for it its there


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## walkman (Nov 8, 2009)

Thanks for the detailed instructions. I bought the repair kit on-line. I couldn't find kits that included the filter and spring. 

The mesh filter wouldn't come off with gentle persuasion so I didn't mess with the jet. 

Fortunately, a thorough cleaning and replacement of the diaphragm solved the problem and the mower is running great again.


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## geogrubb (Jul 28, 2006)

Success is a wonderful sound. Glad we could help. Have a good one. Geo


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