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Discussion Starter #1
So my '02 350 has an issue. First i noticed fuel coming out the carb overflow so i assumed the floats were sticking. Pulled cleaned back on and still leaks once the machine is warm.

However the weird thing is the fuel tank is building pressure. Enough so it is pushing fuel out of the breather tube valve on the fuel cap. Not enough it pools up but enough that i can smell it and if i touch the valve its defiently leaking up there.

Why is the fuel tank pressurized? And are my floats really still sticking after cleaning or is the tank pressure causing fuel to leak out of the carb?
 

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Is the tank vent clear? The carb leaking could be a separate issue, clean the carb and inspect the float needle valve carefully.

I'm not familiar with your model but the petcock may have a filter or screen, check that it is clear.
 

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Discussion Starter #4 (Edited)
Tank vent as in the breather tube coming out of the fuel cap? If so the tube is clear and i have one of those one way breather valves on the tube that lets air in but not out. The tank is building positive pressure and isnt a vacuum considering that fuel is being pushed out the vent on the fuel cap breather line.

Something i noticed is i bought 4 of those breather tube cap vent things for my other quads. 3 are one way and my sons raptor i can blow and suck air. I thought these were only for vacuum relief from the fuel exiting to the carb.


I also want to add this pressure build up was on an almost empty tank 90+ degree weather with 30 mins of just sitting idling. Could my pressure be from just engine heat building up?

Carb probably just needs cleaned again.
 

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It could just be temperature related yes, I've had it before where I've opened the tank and had a shushh noise as air has come out or in.
As you say, it wouldn't hurt to clean the carb out again.
 

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very well could be a bad gas tank cap ?, they vent through the gas cap.
 
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Your tank vent should work both ways. If there is a check valve in it that allows the tank to build pressure I doubt that it belongs there.
 

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Discussion Starter #8 (Edited)
The tank vent was one of those pretty anodized valves that attach to the cap with a couple inches of vent hose instead of the foot+ long tube that runs into the display. I found the same style at the dealership but this one vents both directions. Pretty sure the pressure was caused from sitting idling in the heat and no air flow other than the fan. The previous valve only venting the negative pressure from fuel going to carb and not allowing positive pressure to escape from heat soak caused the fuel to be pushed outward through the cap and valve. 2 way valve solved this as would of going back to the longer stock vent tube but I just like the look of the shorter tube/anodized valve.

Pulled carb again, needle/seat hand a clear-ish residue built up that i could scrap off with my fingernail. Cleaned seat and replaced needle and that stopped the fuel from coming out the overflow tube.

Thanks again everyone!
 

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Good job spandy, glad you sorted it
 
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