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Discussion Starter · #1 ·
Curious, I have an issue with surging engine, it runs smooth, then studders and blows some black exhaust, then runs fine again every 10 seconds or so. I have new everything, but I noticed some gas at the bottom of air intake at the choke inlet, so is this normal, and when could this gas be coming from.

Thanks, Mike
 

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What do you mean by "new everything"? Sounds like you may have a float bowl/needle valve problem. Either there is some dirt keeping it open, the seat is cracked/corroded, or the bowl is not set properly and not closing the valve. This will cause gas to keep pumping into the float bowl until it then pumps into the carb, flooding the engine.
 

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To follow up, and in addition to what Corday said, if you have a solonoid fuel shutoff at the float bowl then it may not be working properly either. Turn the key off and on and you should hear it "click." Also, remove your carb's float bowl and check it for foreign matter and clean the needle and seat. Even a new carb can have problems with foreign material (lint, bits of plastic, etc.) that got into it from the factory.
 

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Discussion Starter · #5 ·
What do you mean by "new everything"? Sounds like you may have a float bowl/needle valve problem. Either there is some dirt keeping it open, the seat is cracked/corroded, or the bowl is not set properly and not closing the valve. This will cause gas to keep pumping into the float bowl until it then pumps into the carb, flooding the engine.
Thanks, I put new carb on, and put premium shell gas to avoid ethanol issues, but now I see fuel dripping into air intake and flooding engine. I suspect a defective carb, or as you say, maybe float stuck. I also now see gas got into oil, so will this excessive fuel intake end up in crankcase?
 

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Discussion Starter · #6 ·
To follow up, and in addition to what Corday said, if you have a solonoid fuel shutoff at the float bowl then it may not be working properly either. Turn the key off and on and you should hear it "click." Also, remove your carb's float bowl and check it for foreign matter and clean the needle and seat. Even a new carb can have problems with foreign material (lint, bits of plastic, etc.) that got into it from the factory.
Thanks, yes, I put new carb on with fuel shut off, and it clicks with ignition. Had to put new connector on, so does it matter which polarity wires go on since it seems to work reversed or not. Just curious if it makes any difference since it is clicking on and off.
 

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Discussion Starter · #7 ·
Fuel shut-off valve should be closed when not using.
Thanks, as it is new carb and shut off, I am curious, the connector was broken so I put new one on and wires were hard to tell difference, so would it make a difference since inverting plug still seems to click fine. If it has no power to shut off, it closes, right, and when on, it opens fuel to bowl is how I understand how it works.
 

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Oil in gas indicates the problem is the shut off valve. Premium gas still has ethanol. If you really want without, find a station that sells non ethanol fuel. The pump is usually at the side or back of the building.
 

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Thanks, yes, I put new carb on with fuel shut off, and it clicks with ignition. Had to put new connector on, so does it matter which polarity wires go on since it seems to work reversed or not. Just curious if it makes any difference since it is clicking on and off.
A solenoid is just a simple magnetic coil switch so polarity doesn't matter. What matters more is if the valve is actually stopping the gas flow.

Another thing that I can think of is how you shut your engine off. If you shut the mower off while it's at full throttle the fuel pressure might be enough to cause fuel to push past the solenoid shutoff valve before the engines stops and then past the float bowl needle valve if it's not sealing tightly. In some old gas farm tractors I ran you had to throttle down and shut off the fuel before shutting off the ignition or they would flood and backfire on you.
 

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Discussion Starter · #10 ·
A solenoid is just a simple magnetic coil switch so polarity doesn't matter. What matters more is if the valve is actually stopping the gas flow.

Another thing that I can think of is how you shut your engine off. If you shut the mower off while it's at full throttle the fuel pressure might be enough to cause fuel to push past the solenoid shutoff valve before the engines stops and then past the float bowl needle valve if it's not sealing tightly. In some old gas farm tractors I ran you had to throttle down and shut off the fuel before shutting off the ignition or they would flood and backfire on you.
Thanks, I assumed the shut off was simple magnet, but it was strange that when I disconnected it while running made engine run smoother, so I would bet it is something to do with shut off perhaps not working properly. So I am putting new carb on to replace this defected one.
 

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Thanks, I assumed the shut off was simple magnet, but it was strange that when I disconnected it while running made engine run smoother, so I would bet it is something to do with shut off perhaps not working properly. So I am putting new carb on to replace this defected one.
While 100% ethanol-free gas is more expensive, especially in these times of high gas prices, I highly recommend it for all small engines. Ethanol attracts moisture, which then causes oxidation that forms varnish and corrodes parts. I used to have trouble starting my small engines after a winter's storage with 10% ethanol gas, even with it stabilized. Since I found a station that carried it and switched to 100% non-ethanol gas, however, I've not had any problems starting my engines after the winter. I still use fuel stabilizer though.

When replacing a carburetor make sure that you order the proper gaskets that you will need too if the carb doesn't come with them. Or, you can do like I usually do and just use gasket maker, which sometimes seals better than the "proper" gaskets do, especially on old motors. I find that a tube of gasket maker is cheaper and handier than keeping lots of different gaskets lying around.
 

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Discussion Starter · #12 ·
While 100% ethanol-free gas is more expensive, especially in these times of high gas prices, I highly recommend it for all small engines. Ethanol attracts moisture, which then causes oxidation that forms varnish and corrodes parts. I used to have trouble starting my small engines after a winter's storage with 10% ethanol gas, even with it stabilized. Since I found a station that carried it and switched to 100% non-ethanol gas, however, I've not had any problems starting my engines after the winter. I still use fuel stabilizer though.

When replacing a carburetor make sure that you order the proper gaskets that you will need too if the carb doesn't come with them. Or, you can do like I usually do and just use gasket maker, which sometimes seals better than the "proper" gaskets do, especially on old motors. I find that a tube of gasket maker is cheaper and handier than keeping lots of different gaskets lying around.
Thanks, will make sure gaskets are correct, and I use gasket sealer as well, so will let everyone know if it was defective carb.
 
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