B&S 12.5 I/C in MTD125/92RH stalls under load

montypython

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I have a MTD RH125/92 (13AC458E600). I think from about 2002 as it came with the house when I bought it 5 years ago and has run great ever since. However recently it has started to want to stall when it is under load. It’s okay on dead level with deck engaged but if you come off clutch too quickly or it’s on a slight incline or full lock it splutters, backfires and will cut out if continued to drive. It has a B&S 12.5 I/C model 28T707)

I recently renewed the air filter, the air filter that was removed had a hole worm through about 1.5 inch in diameter so I guess it was naturally running weak, however the plug looked a good biscuit brown colour but was heavily built up so I replaced with OEM plug of correct type.

After the filter change I the plug is much darker – running rich I would say. I tried adjusting the mixture and removing the air filter but it makes no difference

The mixture screw still has the cover on it so it allows about 2/3 turn of adjustment, it was fully screwed in to the stop, I have tried adjusting but it makes no difference. Is it screw in to weaken?

I seem to get a lot of backfiring and I also noticed air movement I the bottom of the Air filter tray when running.

Any help anybody could offer would be gratefully received as I’m starting think it may be time to change – shame because it has been a great mower

Thanks in anticipation.
 

cpurvis

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Rebuild or replace the carburetor.
 

blueberrymuzik

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It sounds very much like you have some water that has accumulated in the bottom of the tank. My thoughts would be to first unscrew the fuel cap. Then, use a flashlight and look down into the fuel tank while moving the mower back and forth by hand. If you have water in there, you will see if sloshing around beneath the gasoline.
 

montypython

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Rebuild or replace the carburetor.

Thanks Guys, Overhauled Carb - Stripped and blow out with airline and it is behaving much better, still the odd stumble but back to where it was.
Really helpfull thanks again
 

Scrubcadet10

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Could it be low compression?
 
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