I have replaced the needle valve and o-ring, adjusted float then finally replaced with new one, cleaned jets and bowl drain screw with carb cleaner, tested bowl by filling while off the machine, and my carb still leaks from overflow tube but only when running. With fuel on and sitting there with engine off it does not leak, only leaks when running. I started to notice the problem this spring when I saw more and more spots on the garage floor. I am stumped. Anyone have any ideas?

Thanks

 

make sure that your float is set right that is the only thing it could be

 

I don't know if this could be your problem.....but I have an 05 700. When my tank is "topped" off, it will leak out an overflow. Just a thought, I do not know if it will help you, but see if it is only happening when the tank is topped off. As long as the level is about 1-2 inches below the neck of the tank it will not leak on mine.

 

Almost every 4, 5, 6 and 700 carb engines I have ever seen drips a little fuel out of the carb overflow tube when running. I have never spent much time trying to fix it because they all run good and no one complains. My own 600 has done this since new and has 2500 miles on it with no rich running problems.
I run in a lot of steep stuff and have never had the engine die when the ATV was idling at weird angles while I figured out how to negotiate my next move.
I rode a 500 EFI in some of the same stuff today and was impressed with its performance. No fuel smell came from it. That was the first time I had rode a 500 that far and was lacking a little power when comparing to the 600 carb I am used to riding.

 

wastedone, before I replaced the float I tried adjusting the original one several times, in the correct direction. more than one mechanic told me it should not have to be moved more than a 16th of an inch. then I got a new one thinking perhaps I had a hole in the original, still leaked.

now Charlie, I feel a little better knowing I am not alone with my leak problem, however, I think at $5000-$7000, these machines should not leak. mine runs fine also, but to me, gas drops in my garage are unacceptable considering what I paid for the damn thing. I'm not pissed at you, just pissed. as consumers, we should not accept failures like this, we work hard for our money and deserve better. we consumers are responsible for maintaining standards of quality, if we don't, we only have ourselves to blame for inferior products.

sermon over.

 

I should'nt say I have never spent much time on this problem because I have done all you have done and more. I would like to hear if anyone else has had this problem and fixed it. Vibration is the what I think is the cause. At certain speeds the engines natural harmonics can slightly aereate the fuel.

Engines in Polaris ATVs are unique because they stand alone from the transmission and have more vibration. The transmission in other brands that are attached to the engine act like a heatsink for vibration with its mass.

It might be the float height needs to changed to make up for the excess vibration. But this may lead to fuel starvation though during high fuel demand situations. Anyone else played with this?

 

Perhaps there are others with the problem, but they don't notice because they park the machine on a surface that doesn't show the drops. The fuel smell isn't overwhelming and many could be ignoring the leak. You bring up a good point Charlie with the vibration theory, these things do send out some vibrations. Maybe it's just another "Polaris Quirk". [img]i/expressions/face-icon-small-sad.gif[/img]

 

We’ve owned about 9 Sportsmans over the years (I’ve lost track) and this only happened to one of them. When my ’01 500 HO had about 7500 miles on it the float bowl overflow tube started leaking fuel while running, just as you describe. I like playing with suspension, electrical, etc but I don’t mess with carbs so I took it to the dealer. The wrench there (a guy I trust) replaced the needle and seat, same problem. Then he replaced the float, same problem. Then he spent an ungodly amount of time adjusting the float for the minimum amount of fuel in the bowl that would allow the machine to run. Same problem. His efforts reduced the leakage quite a bit but it never went away completely. I wasn’t aware it was a common problem until reading this thread.

 

maybe we should start a "leaky carb overflow" support group, sounds like something we are going to have to deal with as opposed to fix. I'll try to send an email to Mikuni, maybe there is a service bulletin we don't know about. It is comforting knowing I am not alone with this problem, but discouraging at the same time because the problem should have been solved long ago.

 

did anyone replace the bowl itself? I tested mine while off the machine by filling with fuel and it didn't leak...