poor running mower

ssergel

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#1
I have a mtd mower with a briggs & Stratton 500 series engine, it starts right up every time but after a few minutes it starts to run like its bogged down, even if it is running on the driveway. I have cleaned carb many times, even with seafoam as you would on your car intake and it still runs the same. Gas is good I regularly add stabilizer to the gas, plug and air filter are good. Any Ideas. Thanks
 

billr

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#2
Is it mis-firing, or just poor on power? A few common possibilities with B&S engines: float needle leaking and flooding carb, filter screen inside tank clogged and starving carb of fuel, tank filler-cap vent plugged and starving carb of fuel, valve-to-lifter clearance has gone a way and holding a valve open. Is this a flat-head engine or OHV? Have you taken compression right after it has warmed up and gotten lazy?
 
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#4
Sounds perfectly normal if you are using E10. Just a handful of brand new engines claim you can use E10.
 

nickb2

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#5
I usually never post in small engine threads, I would like however to know what year it is. I am seeing two different carbs for the Mtd 500 series. Maybe I am mistaken.

Anyways, as Bill said, maybe an overhaul of the carburetor/fuel system is needed here. A four stroke like this should not vamp down unless it is a fuel issue. Post back year and maybe model number. Is it a 3.5hp or 4hp?

@Bill, think it is a OHV. Op will confirm.
 

billr

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#6
It is the flat-heads where I often find the valve clearance "going away", that's why that info is important.
 

ssergel

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I usually never post in small engine threads, I would like however to know what year it is. I am seeing two different carbs for the Mtd 500 series. Maybe I am mistaken.

Anyways, as Bill said, maybe an overhaul of the carburetor/fuel system is needed here. A four stroke like this should not vamp down unless it is a fuel issue. Post back year and maybe model number. Is it a 3.5hp or 4hp?


Here is the model #10t502
type-0457b1
code-09052255

Thanks for the help, were is a good place to lo online for a rebuild kit for the carb?
 

billr

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#9
That model # (10t502) comes up as a flat-head for me. However, if valve clearance is bad, I would expect that to be worse when cold (won't start). Again, take compression when the engine is warmed-up and getting lazy.
 

ssergel

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#10
I remove carb ad soaked it over night and it runs much better now, not completely smooth but it stays running. The rpm's go up and down a bi but it's running much better. I guess his means a carb issue. doesn't look like there's much there to rebuild so do you have a good website for replacement? I tried sears and ereplacemnt parts.com with no luck.

Thanks for the help.
 

billr

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#11
I have never replaced carb parts on a small engine, just blowing them out with air and getting the gaskets "wet" again with fuel does the trick. If there is any crusty crud or varnish on things, I scrape that off with a wood stick or fine wire brush. I think the biggest problem is that the float-bowl goes dry, then the gasket on top dries out and the little-bitty air-bleed passages up there leak enough to throw fuel metering out of calibration. Run it for a while more, it may self-heal as the gasket swells.
 

billr

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#12
I have never replaced carb parts on a small engine, just blowing them out with air and getting the gaskets "wet" again with fuel does the trick. If there is any crusty crud or varnish on things, I scrape that off with a wood stick or fine wire brush. I think the biggest problem is that the float-bowl goes dry, then the gasket on top dries out and the little-bitty air-bleed passages up there leak enough to throw fuel metering out of calibration. Run it for a while more, it may self-heal as the gasket swells.
 

nickb2

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#13
I have never replaced carb parts on a small engine, just blowing them out with air and getting the gaskets "wet" again with fuel does the trick. If there is any crusty crud or varnish on things, I scrape that off with a wood stick or fine wire brush. I think the biggest problem is that the float-bowl goes dry, then the gasket on top dries out and the little-bitty air-bleed passages up there leak enough to throw fuel metering out of calibration. Run it for a while more, it may self-heal as the gasket swells.

Posted twice, maybe hit enter twice, but very good advice. as for link, try this one.

http://www.partstree.com/parts/?lc=briggs_and_stratton&mn=10T502-0457-B1&dn=37180004