DYS4500 with 24hp B&S Intek vtwin idle issues

A

ACDNate

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I'm relatively mechanically capable but my experience lies predominantly with motorcycles.

The lawn mower is a Craftsman DY4500 with a B&S 24hp Intek motor. The mower is a buddies I'm trying to help get running correctly.

Symptoms:

Mower will start with choke and initially run correctly.

After a short period of time running the mower will begin to rev down and back up on it's own. This occurs regardless of throttle position. Looking underneath the carb I can see a vertical linkage moving up and down at the same time the engine revs change. Under load while driving with deck engaged the symptoms are exaggerated even more.

What I've done so far:

Before noticing the correlating linkage movement I went through the mower completely.

Air filter clean and free. Spark plugs clean and firing cleanly. Fuel clean and fresh.

Fuel flow through the filter didn't look very good (compared to what I'm used to). The fuel pump was replaced suspecting the issue to be insufficient fuel flow. Filter clean.

I noticed what the manual told me to be a fuel cutoff gadget (technical term) attached to the carb bowl and connected to a 2 wire harness. I tried running the mower with that disconnected and saw no change in symptoms, so I plugged it back in.

What would make the mower rev up and down on it's own??? Where to go from here?

Thanks for any advice or direction anyone can offer.
 
pugaltitude

pugaltitude

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I would start off with cleaning the carb.
Sounds like a slight blockage in one of the small orifices.
Whats your model, type and code?
 
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ACDNate

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Unfortunately I don't have the model code and type handy.

Would a blockage cause that linkage to move though? The moving linkage has me really perplexed.
 
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ILENGINE

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That linkage moving is the governor trying to maintain engine speed The governor spring speeds the engine up, and the governor gear inside the engine slows the engine down. when an engine is too lean the engine like with a partially clogged carb. the engine starts slowing down and the governor spring brings the engine speed up, then it decides it is too fast so it slows back down, causing the hunting and surging effect. Usually that means that the idle circuit in the carb is dirty, but most of the time will smooth out under load. It sounds like from your situation it may also involve the high speed circuit, or maybe something goofy with the governor itself.
 
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ACDNate

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Ah ok. That makes sense. I'm not at all familiar with the governors. I'll pull the jets and make sure they are clean.
 
wjjones

wjjones

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ACDNate said:
I'm relatively mechanically capable but my experience lies predominantly with motorcycles.

The lawn mower is a Craftsman DY4500 with a B&S 24hp Intek motor. The mower is a buddies I'm trying to help get running correctly.

Symptoms:

Mower will start with choke and initially run correctly.

After a short period of time running the mower will begin to rev down and back up on it's own. This occurs regardless of throttle position. Looking underneath the carb I can see a vertical linkage moving up and down at the same time the engine revs change. Under load while driving with deck engaged the symptoms are exaggerated even more.

What I've done so far:

Before noticing the correlating linkage movement I went through the mower completely.

Air filter clean and free. Spark plugs clean and firing cleanly. Fuel clean and fresh.

Fuel flow through the filter didn't look very good (compared to what I'm used to). The fuel pump was replaced suspecting the issue to be insufficient fuel flow. Filter clean.

I noticed what the manual told me to be a fuel cutoff gadget (technical term) attached to the carb bowl and connected to a 2 wire harness. I tried running the mower with that disconnected and saw no change in symptoms, so I plugged it back in.

What would make the mower rev up and down on it's own??? Where to go from here?

Thanks for any advice or direction anyone can offer.
Click to expand...



I have a model# that should be the same, or close to it 446677-0463-E1 it sounds like the carb needs a good cleaning to me. Does it look like the one in my avatar? Mine did the same thing the float bowl was full of debris, and after cleaning it, and the carb jets out it runs fine now. After cleaning it run a few tanks of fuel through with fuel stabil in it.
 
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