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I'm trying to fix a problem with gas leaking from the air filter. Forum member Two Stroke thought my cork float might be bad. --- Thanks, Two Stroke --- How can I determine if it is good or bad? It's on a Lawn Boy model 5247, made in 1980, F100 engine, the late model carburetor. The cork float isn't chipped. I think the varnish looks okay, ... though I'm not sure exactly how it would look if the varnish was bad. The natural tan color of the cork has lots of black spots on it. I discovered the float level was wrong. It was set at 5/16". I've corrected that to the 7/16" spec. Could that have been the problem? The needle and seat seem to be working okay. Another question: What chemical should I clean inside the plastic carb with? I was afraid Chemtool would melt the plastic. Mine didn't look dirty, but I cleaned it with Dawn dishwashing detergent. I used a thin wire on the passages, and cleaned the screen, too. I'd like to know how to tell if the cork float is good or bad before I put the carb back on and try it again. Thanks, fellows.

I'd pour some gas into a bowl and see if the cork floats, or absorbs fuel. Is the main jet the right size? It could be pulling too much fuel, causing the leak. Your carb may have the plastic jet. I'd try using the fuel mix to clean the carb, and then dry it with low vol compressed air. Good luck!

Fireman 123 said:

I'd pour some gas into a bowl and see if the cork floats, or absorbs fuel. Is the main jet the right size? It could be pulling too much fuel, causing the leak. Your carb may have the plastic jet. I'd try using the fuel mix to clean the carb, and then dry it with low vol compressed air. Good luck!

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Thanks, Fireman. I put the cork float in a bowl of gas about an hour ago. So far, it's floating okay. I'll let it sit all night and check it in the morning. The plastic main jet does not have a number on it. You said it seems like the carb is pulling too much fuel. I agree. I cleaned the carb again like you suggested and blew it dry. So, its extra clean and looks fine. I'll put the carb back on in the morning and see if gas still leaks from the foam filter. Maybe changing the float setting helped. From my research, it looks like there were three carb models used on the F100 engines. The first two had an "altitude adjustment" screw on the side. It was to fine tune it. The third ("late mode") carb is the one I've got. It doesn't have an altitude adjustment screw. Instead, it has a hex headed screw, and it looks like Lawn Boy called it an "adjustable fuel flow needle valve." If that screw is out of adjustment, would it cause gas to drip from the filter?

Gene123 said:

... Instead, it has a hex headed screw, and it looks like Lawn Boy called it an "adjustable fuel flow needle valve." If that screw is out of adjustment, would it cause gas to drip from the filter?

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I don't think that could cause gas to flow out of the carb -- it looks like there's some problem with the float, if it's still flowing like that. Does your carb have a plastic float valve? If so, it seems to me that those could wear out sooner. If that valve is leaking (even a little), that could be the problem.

The over-sized main jet will cause the engine to run rough, and spit fuel out of the carb while running, not when turned off. If the fuel runs out with the engine off, then yes you have a float issue.

Two-Stroke said:

I don't think that could cause gas to flow out of the carb -- it looks like there's some problem with the float, if it's still flowing like that. Does your carb have a plastic float valve? If so, it seems to me that those could wear out sooner. If that valve is leaking (even a little), that could be the problem.

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Thanks for your help. It has a cork float, not a plastic one. I left it in a bowl of gas overnight, and this morning it was still floating just fine. I'll try what you and some of the other fellows have suggested. This is on a model 5247 (1980). I'm not sure how long the mower has been sitting unused. Oh, I posted a hello and introduction to myself on the forum this morning. I signed up a couple of days ago.

Fireman 123 said:

The over-sized main jet will cause the engine to run rough, and spit fuel out of the carb while running, not when turned off. If the fuel runs out with the engine off, then yes you have a float issue.

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Thanks, Fireman. I believe I'd better check it both ways like you suggest. The float floated all night in a bowl of gas. I've dried out the filter. I'll put the carb together and get it on the machine today. Before I start it, I'll check what you've mentioned. I'll just turn on the gas, let it sit awhile --- then see if gas has saturated the foam filter and started dripping again.

Re: How do I check a cork float to see if its good or bad? 5/19/2015 follow up.

This is a 5/19/2015 follow up to help many viewing this original 4/12/2012 post: The problem with gas leaking out the air filter was solved by installing a new needle & seat. The cork float could have been the problem, but it tested good. Thanks to forum and nice fellows who provided good, correct advice. Now (three years later), my 1980 model 5247 starts on the second or third pull and continues to run perfectly. However, the carburetor speed control lever is broken off, and I wish I could find a new one. If someone could help locate one, perhaps the knowledge could could help many of us. It's a part easily broken off. I'll post a new thread today wanting to locate this part. Thanks, gentlemen.

should be able to find a vane for that carb through ebay or partstree.

If gas drips out of the carb. air filter housing when the motor is not running and the float is ok and the float level is with in spec. then you have a needle and seat that are defective.

LB8210 said:

If gas drips out of the carb. air filter housing when the motor is not running and the float is ok and the float level is with in spec. then you have a needle and seat that are defective.

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Thanks. That's what it turned out to be. The float checked out okay.