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KenH

520H Gets Too Much Fuel?

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KenH

Hi-

I'm trying to get my Dad's late '80's 520H running for him.  It will start, but soon floods out, eventually with raw gas soaking the air filter and housing.  I can disconnect the fuel line and it will start again and run fine until the fuel in the carburetor is consumed. While the line is disconnected, a container placed under the line gets filled rapidly with a steady stream of gas (rather than a pulsed stream).  Is there a malfunction with the fuel pump or is there some other issue?  Thanks in advance for any suggestions!

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r356c

:text-welcomeconfetti:  to :rs:!

 

Usually it is lack of fuel problems... not the case here.

 

The carburetor float is not closing the float needle when the float bowl is full.

 

The float itself could be leaking and not providing the force required to push the needle closed.

When the float is disassembled from the carb and shaken, it should not have any fluid in it. If it has any gas inside, it needs to be replaced.

 

The needle could have some crud on it's sealing surface preventing it from fully closing.

Worse case is the rubber seal of the the float needle has deteriorated to the point of not being  able to seal. This will require replacement. Otherwise, cleaning should be all that is needed.

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lynnmor

Good advice from r356c, let me add that you should do an immediate oil change since you likely have gas in the oil.

 

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KenH

Thank you both!  If the carburetor needs to be replaced, would you go back with the same model or a different one?

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SylvanLakeWH

:text-welcomeconfetti:

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N3PUY

How is gas getting "UP" into the air filter.  Isn't the air filter above the carb?  

Is the crankcase full of gas and being sucked into the air filter thru the breather?

 

 

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KenH

Yes, but gas is spraying out of the top of the carb, collecting in the enclosed housing and wicking up into the filter.

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Achto

 

1 hour ago, KenH said:

Yes, but gas is spraying out of the top of the carb, collecting in the enclosed housing and wicking up into the filter.

One other thing to check on the carb. There should be a vent hole in the carb from the bowl up to the throat of the carb. If this is plugged air can not escape from the bowl as it fills with gas. This will cause gas to shoot out of the main jet into the carb throat at an enormous rate.

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lynnmor
3 hours ago, KenH said:

Thank you both!  If the carburetor needs to be replaced, would you go back with the same model or a different one?

Unless there is extreme wear or corrosion, there is no reason to replace.  You do not want the mid to late 90's carbs that run lean. 

 

I saw a carb on eBay that may be what you want.  Rebuild kits are/were available on eBay as well, but don't use the manifold to block gaskets, they are junk.  The needle valves is those kits need the sharp edges in the float groove to be dulled a bit so they don't hang up.

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N3PUY

Are you sure it is running on both cylinders?

 

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KenH

I don't know. It sounded fine/normal for the limited amount of time I had it running.  How can I determine this? As you can probably telll from my posts, I have very little knowledge of these tractors. Was visiting my Dad earlier this week and he asked me to start his tractors (he's 92).  I was only able to spend a limited amount of time with it, so I'm learning as I go thanks to this forum. 

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N3PUY

Remove the front spark plug wire and ground it to the cylinder head.  

Start it.

Reinstall that wire and do the same to the rear spark plug.

Start it.

Should run the same both times.

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r356c

This Walmart product has resurrected two carbs for me this season with minimal disassembly.

It is a good idea to wear safety glasses when clearing all the fuel passages clogged with ethanol gas funk.

 

 

WalmartCarbCleaner.jpeg

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