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Carburetor Leaking Fuel

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James

03-16-2002 12:53:16




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The Carburetor on my 12HP Briggs engine is leaking fuel. Although I do not know much about these things and still learning, I have taken the carb off and cleaned the bowl, the float, and sprayed inside the carb. Still leaking fuel. Any help or suggestions will be appreciated.




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Mike

03-25-2004 12:43:39




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 Re: Carburetor Leaking Fuel in reply to James, 03-16-2002 12:53:16  
I've been a small engine mechanic for 30 yrs.I think that I can help ya.If your carb.is leaking from out of the throat,your float has a hole in it causing gas to enter and weighing it down and never letting the needle valve to cut the fuel off.get a new float.if leak is at the top of bowl get new bowl gasket,if leak is under bowl get a new bowl-nut gasket.

You can reach me from my website too at:
www.freewebs.com/lawnmowerrx OR
www.the lawnmowerrx.com

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James

03-17-2002 14:54:48




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 Re: Carburetor Leaking Fuel in reply to James, 03-16-2002 12:53:16  
Thanks for the suggestions. You folks are right and there could be several reasons for the fuel leak. Today, I took the bowl off and removed the float to see what is happening. I noticed a lot of rust there. I did a good cleaning of all parts and put them back on. I have not yet tested the carb but now have a better understanding of the problem and what needs to be done.

I know the valve connected to the float controls the fuel coming in. But what is the function of the valve at the bottom of the bowl? Are both of these valves called "Needle Valves"?

- James -

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slughammer

03-18-2002 10:33:22




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 Re: Re: Carburetor Leaking Fuel in reply to James, 03-17-2002 14:54:48  
Look at the float stuff that the other guys mentioned, also look real close at the needle and the retention spring. The spring should clip onto the needle and have a leg that goes over a tab on the float. If the float goes down, the retention spring will actually pull the needle down. Make sure the spring is on the right way. Also look at the needle and the seat; you'll have to look real close, but the tip of the needle is most likely rubber and the seat is part of the carburator. I use a pair of tweezers to pull the retention spring off of the tab on the float and then you can get the needle out and clean varnish off of the surfaces of the seat and needle. The needle at the bottom of the bowl is most likely the jet. Does it project toward the center of the carb and there is a tiny hole in the bowl that would allow gas to the side of the needle, then this is the jet? If you took it out, you'll have to turn it in all the way and then back it out about 1.5 turns to get started again; adjust from there. There are some real good books for Briggs out there; just saw one a Home Depot that covers a whole series of motors($10). Good Luck - Slughammer

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James

03-18-2002 19:59:47




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 Re: Re: Re: Carburetor Leaking Fuel in reply to slughammer, 03-18-2002 10:33:22  
Slughammer,

Thanks for your help and suggestions. You are absolutely right and you really know this stuff. I took the bowl off again. The hing and spring on the needle valve came off very easily. Actually, I think the spring was not properly attached to the tab, and I really do not know how it is supposed to be attached. Anyway, the needle and the seat look clean and in good shape. I think the problem may be with the spring not holding it.
Because after putting the carburetor back and testing it today, it was leaking again as before.

About the jet needle at the bottom of the bowl, it is leaking fuel from there too. It has a washer and nut holding it. I just took it off and cleaned it. I did not touch the adjustment screw on it. So, that is where we are.

- James -

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Slughammer

03-20-2002 09:06:43




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 Re: Re: Re: Re: Carburetor Leaking Fuel in reply to James, 03-18-2002 19:59:47  
James, The spring can serve two purposes when it is correctly installed. 1. Keeps you from having the needle fall out when the carb is apart. 2. Could pull a needle down if it is stuck against the seat (pull it out of the off position). If the spring is in the wrong way it could be binding the needle or causing the tab on the float to bind on the end of the needle vs. actually pushing it up. That said, the whole thing could actually work without the spring. Not saying to take the spring off, just hope that this helps you understand the spring enough to put it back in correctly. In the normal position, the needle is on top of the tab on the float and the spring is going around to the bottom of the tab. What holds the bowl onto the rest of the carburator? Is it three screws from the top; or one bolt from the bottom? Does the adjustment screw on the bottom go straight up; or is it at a 45 deg angle. The bowl should allow fuel to get to the shank of the adjusting screw, can you fill the bowl and see if it is just leaking past the adjusting screw. The threads should be sealed and gas should not be coming out of there; may not be a float problem at all. Sounds like you've had it on and off the engine and apart several times; it may be time to attach the carb to a board and put a coffee can under it, attach a piece of fuel line and start testing.- Slughammer

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tom

03-17-2002 14:09:17




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 Re: Carburetor Leaking Fuel in reply to James, 03-16-2002 12:53:16  
Cleaning doesn't always fix this problem. Best thing is to replace the needle valve and seat. Also, make sure the float, floats. They can get pin hole in them, allowing gas inside, and they sink. They can also float in water, but sink in gas, as gas can flow through smaller holes that water sometimes can not.

You may also need to adjust the float. It should seat level when closed Hold carb body upside down, and check. Plastic floats are not adjustable however.

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Roger

03-16-2002 13:31:58




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 Re: Carburetor Leaking Fuel in reply to James, 03-16-2002 12:53:16  
Your float may have a leak in it which will cause it to sink and allow fuel to keep entering the carb bowl. Think of what would happen if the float in your flush box of your toilet was not floating. Same scenario. Alternately, there is something jamming the float needle valve which keeps it open. That is where I would start. Check your oil level. The gasoline is probably going into your crankcase too, with much unhappiness soon to follow.

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