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Thread: Carb is leaking fuel??

  1. #1
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    Angry Carb is leaking fuel??

    My 1991 Polaris Trail Boss 350L is leaking fuel from the carb overflow tube like a faucet. Does anyone know why and what I can do to fix this?

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    Member Dirtofak's Avatar
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    I would believe that your float bowl valve is sticking or your float no longer floats. Remove the carb, take off the bowl and inspect. Replace the valve and set the float height. I don't have specs with me as I am outside..... sorry. Do not soak the carb for a long time!!! You can ruin it. While you are there inspect the boots and clean out the drain tubes.

    Mike

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    Member alaskachuck's Avatar
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    I have had this happen on my "toys" I usually just give the carb bowl some light taps to loosen it up. It usually happens after a winter of storage
    Grandkids, Making big tough guys hearts melt at first sight

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    Moderator LuJon's Avatar
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    I agree w/ chuck. Try whacking the float bowl and if it stops and runs good then problem solved. If it doesn't fix it then you will need to yank the carb and go clean it up or perhaps replace the float. On some vehicles that have a nut on the bottom of the bowl I have been able to turn the fuel off, remove the drain nut and then use a can of carb cleaner w/ the lil' straw and just poke it up the hole and spray the crap out of it without taking it off the rig.

    So there is your 1 minute, 10 minute, and 3 hour solutions. So worse case you should be out ripping around in less than one evening.

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    Thanks guys for all the info. Hopefully I will be able to fix it tomorrow.

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    Check your oil for gas, or just change it to be safe, or you could wuin you engine.

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    Member mod elan's Avatar
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    Good advice to change the oil on a flooded engine. But in this case it is a 2 stroke so doesn't apply here. The needle & seat need changing or floats are stuck. On that rig I would lean toward a new needle & seat.

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    Moderator LuJon's Avatar
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    Quote Originally Posted by mod elan View Post
    Good advice to change the oil on a flooded engine. But in this case it is a 2 stroke so doesn't apply here. The needle & seat need changing or floats are stuck. On that rig I would lean toward a new needle & seat.
    you think needle and seat? Honestly after 20 years a carb rebuild would be a good idea regardless of the exact source of the immediate symptom. That said I would expect a needle/seat problem to result in a much slower leak than a stuck float.

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    Member mod elan's Avatar
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    What is changed/fixed during a Mikuni VM carb rebuild? I don't think we could eyeball the difference in flow between a stuck float and a bad needle & seat.

    What is the history on the machine? Last operated? Fuel just coming out the overflow tube or coming out the throat of the carb? Have you checked to see if the vent line on the tank is plugged? This would pressurize the tank on a warm day and blow by an already worn needle & seat.

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    Default I did fleet repair on yamaha wave runners

    Those macuni carbs wore out the needle and seat all the time .
    the 2 stroke is notorious because of it's high vibration. The units I worked on had no real float, but a diaphram. Once I found a blond hair that caused the flooding . It had passed all the filters and the needle . it was about 6"long . Even so the needle guide wears sevirely , so that there would be intemintent function, but not reliable. Be careful, there are some plastic valves in there too, almost as thin as celephane.Some of these carbs, actually sent pressure to the fuel tank, to help the flow. Some of these used the macuni fuel pump , that works off the crank case pulse, It is not likely to over pressureize, but be aware of how it functions, old cracked hoses can leak that precious pulse, and starve the fuel.
    there are relief valves on the tank to prevent over presurization, if they plug or fail , and the pressure rises significantly( more than 2 psi) It could also be a significant factor in flooding.
    If it is merely leaking externally ckeck the screws and or repllace the gaskets, ther rubber usually.use no glue.
    Just my opinion

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    I have a 250 Yamaha that wears needles and seats occasionally. That little carb can fill the air box (about a quart of gas) in just a few minutes when the needle and seat is leaking. The repair is to replace the parts. Don't try to spray your carb with carb cleaner to clear it. You'll be sorry.

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    Quote Originally Posted by mod elan View Post
    Good advice to change the oil on a flooded engine. But in this case it is a 2 stroke so doesn't apply here. The needle & seat need changing or floats are stuck. On that rig I would lean toward a new needle & seat.
    It a 2 cycle? It uses mix gas? I did not know that. Will, if that the case I would open the lower drain on the crank case and drain any gas that may be in it. Assuming it has a drain.

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