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Sick B&S Surging 4hp


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05-19-10, 10:44 AM   #1  
Sick B&S Surging 4hp

I have the above engine B&S 4hp Quattro about 9 years old. I have the carbureator mounted on the gas tank. The carberator is made of the hard plastic material. I have replaced the diaphram for the carbureator. It will crank but while it is running it is reving up and down like it cannot get the proper amount of air/gas mix. I have done the following: New Diaphram
Cleaned the carberator with Gumout cleaner
Inspected the jets - clean
Inspected the fuel intake line - good
Inspected and cleaned air filter
Added a new spark plug
Gas Tank is clean
Gas is Fresh

Here is what I have noticed: WHen I manually press the governor to give it more gas it does still miss and cut out.

Note: When the fuel tank gets low it does run so much better and then runs out of gas. This occurs in the last 2 minutes of running.

My pull start rope does need some adjustment -- in other words I am not getting a good full spin. But this has not been a correlation with the missing and surging from the fuel issue.

What is the likely hood that the springs are the sole issue and I need some help and strong suggestions. THANKS

 
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05-19-10, 10:53 AM   #2  
Are your results with or without the air filter installed?

 
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05-19-10, 11:04 AM   #3  
Posted By: glassc I have the above engine B&S 4hp Quattro about 9 years old. I have the carbureator mounted on the gas tank. The carberator is made of the hard plastic material. I have replaced the diaphram for the carbureator. It will crank but while it is running it is reving up and down like it cannot get the proper amount of air/gas mix. I have done the following: New Diaphram
Cleaned the carberator with Gumout cleaner
Inspected the jets - clean
Inspected the fuel intake line - good
Inspected and cleaned air filter
Added a new spark plug
Gas Tank is clean
Gas is Fresh

Here is what I have noticed: WHen I manually press the governor to give it more gas it does still miss and cut out.

Note: When the fuel tank gets low it does run so much better and then runs out of gas. This occurs in the last 2 minutes of running.

My pull start rope does need some adjustment -- in other words I am not getting a good full spin. But this has not been a correlation with the missing and surging from the fuel issue.

What is the likely hood that the springs are the sole issue and I need some help and strong suggestions. THANKS
Those explanations in bold are some what contradictory as far as diagnosis, so I am not certain of the symptoms.
Assuming you meant the same thing by both, the engine revs up and down, that would be surging and caused by a fuel restriction. You may still need to clean the carb.
If it is spitting and cutting out, sputtering....??? AND when it runs out of fuel it smooths out (which would cause a lean condition) then it sounds like it is running rich. Does this have a choke or primer?
I would check the diaphragm to make sure it did not get pinched or out of place...
Also post the model of the engine.

 
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05-19-10, 11:03 PM   #4  
Yep, I'd agree...the diaphragm is still a problem. Sometimes these plastic carbs get warped and don't hold the diaphragm in place like they should, allowing it to pull in between the 2 screws on either side of the intake pipe opening.


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05-21-10, 09:24 AM   #5  
It is both ways with it off or on it is still surging. What I have noticed it is using twice as much gas than before this started. Also, since the diapharm is new I made sure it was seated properly. Still a problem.

 
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05-21-10, 09:27 AM   #6  
The diapharm is aligned properly and I reseated it back on the surface. It still has a problem. Thanks anywhere else to check possibly. Jets clean, intake filter clean. Gas new.

 
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05-21-10, 06:04 PM   #7  
Post the the engine model, type and code usually found stamped in the metal shroud just above the spark plug so we know which one you have. Have a good one. Geo

 
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05-25-10, 02:20 PM   #8  
Exact same problem with my 9 year old Quattro 4.0

What he says is exactly the way mine is doing. Just before it runs out of gas it smooths out. I took off the air filter and it still surges. Also using more gas than normal.

 
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05-25-10, 05:58 PM   #9  
Posted By: geogrubb Post the the engine model, type and code usually found stamped in the metal shroud just above the spark plug so we know which one you have. Have a good one. Geo

The model number is the Briggs and Stratton 10A902. Type 2139E1; code 99042255

 
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05-25-10, 06:01 PM   #10  
See above both ways? Any other suggestions sounds like warped carb what about you? What is a good source for a carb and what is the cost.

 
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05-25-10, 06:45 PM   #11  
Sounds like a carb is in order for your engine. The carb is about $35.


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05-25-10, 08:09 PM   #12  
Posted By: glassc The model number is the Briggs and Stratton 10A902. Type 2139E1; code 99042255
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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05-26-10, 03:24 PM   #13  
Just for a goof, if you have replaced the carb diaghragm & you're sure it's O.K & you have good spark,, Check the valve clearance... I haven't seen it this year, but last year I had 1/2 dozen that would act like a bad carb & they turned out to be valve adjustments (on the L head engines) Just throwing thoughts out there... Roger

 
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05-31-10, 12:53 PM   #14  
Great instructions Geogrubb always highlight the importance of the Thin Diaphram goes next to the gas tank and the gasket to the carburetor side. When you do it backwards it will not work. Man it runs better than it has in 3 years overall. The surging had been a problem for 6 weeks. Thanks a bunch.

 
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