Hello,

So I let my brother ride the bike and followed on my Suzuki. I noticed that during his accelerations I could see a mist coming off the right side of the bike, and smelled gas. I found a small rubber hose leading down the right side of the bike (coming off around where the center stand folds up to) running from the gas tank. It connects to the gas tank on the bottom about two inches (~5cm) from the right side of the tank, on the bottom. This is about halfway along the gas tank and can be seen with a few inches of clearance from the fairing. I haven't found any reference to this spout that the hose connects to, and am unsure how to stop it from leaking. I don't want to block it, without know what's going on, for fear of causing another problem. I do have the old style tank on my bike, so maybe this was an old design that was fazed out?? Any help or ideas about this would be very much appreciated. I also hope this improves my fuel mileage a little bit as I have noticed that I consistently get low 30's and am not too heavy on the throttle. 

Thank you for looking, and any advice.

John,
There is a fuel overflow pipe running out at that point from a stub inside the tank at the filler cap. A second outlet drains fluid from the gulley around the outside of the fill cap.
The config of exactly how these outlets drain is slightly different on the earlier tanks but the function is the same. They should just route from the bike where you describe and don’t go into anything.
The only time I have seen fuel from this outlet apart from when overfilling the tank is when someone connected the rubber line from the fuel pump strainer onto the overflow stub (this is a bad thing).

John A wrote:I do have the old style tank on my bike, so maybe this was an old design that was fazed out??

The old-style tank has a non-return valve as part of the fuel return port on the left side. The valve had a couple of problems. It could seize affecting fuel delivery and it could buzz loud enough to cause distraction. The later tanks eliminated that valve, replacing it with a metal fuel line that went from the intake port to the top of the vapor collector.

Does the fuel filler opening have a flapper valve in it that the gas station pump nozzle needs to push open?

The hose attached to the port on the underside of the tank that you've described shouldn't drip fuel very often or for very long, if at all. I'd check it for a breakage somewhere along its length that is allowing fuel infiltration.

John,
Laitch knows loads more about this stuff than I do.
FWIW my 85 RT consistently delivers 38 to the US Gallon pulling a chair under interstate conditions so that, at least, should be an aspiration.
Stu

Laitch wrote:

John A wrote:I do have the old style tank on my bike, so maybe this was an old design that was fazed out??

The old-style tank has a non-return valve as part of the fuel return port on the left side. The valve had a couple of problems. It could seize affecting fuel delivery and it could buzz loud enough to cause distraction. The later tanks eliminated that valve, replacing it with a metal fuel line that went from the intake port to the top of the vapor collector.

Does the fuel filler opening have a flapper valve in it that the gas station pump nozzle needs to push open?

The hose attached to the port on the underside of the tank that you've described shouldn't drip fuel very often or for very long, if at all. I'd check it for a breakage somewhere along its length that is allowing fuel infiltration.

The fuel filler opening does not have a flap on it. What I noticed with the fuel leaking was that it only ever leaked when the throttle was opened pretty well, and it would stop ejecting fuel after a few seconds. could it be that it's bleeding fuel there to reduce increased pressure?
Also, would it cause damage to put an endcap on the stub to stop fuel from flowing out? I was thinking of doing that but wasn't sure if it needed to eject fuel there under certain conditions. I would still be able to pull off the endcap if the tank was ever overfilled to drain it, but I'm not sure about that solution. 
I will look for a breakage in the line after I ride back home. Hopefully the fuel level will be low enough to inspect it.

How full was the tank and when did you refill?  Gas coming out of tanks in the ground at gas stations is fairly cool. Put it in a K and have it heated in the tank and it will expand some.

duck wrote:How full was the tank and when did you refill?  Gas coming out of tanks in the ground at gas stations is fairly cool. Put it in a K and have it heated in the tank and it will expand some.

The tank had just been filled all the way. However, my brother mentioned seeing it on the way to the station while I was riding the K and the tank was half full.

Laitch wrote:The hose attached to the port on the underside of the tank that you've described shouldn't drip fuel very often or for very long, if at all. I'd check it for a breakage somewhere along its length that is allowing fuel infiltration.

To be clear, what I believe should be inspected for brakage is the metal line within the fuel tank that is connected to the port that exits on the underside of the tank.

The little hole on the left of the fuel filler drains into a metal pipe that passes through the tank and comes out underneath. A break in it will leak gas. You can get a thin wire or a pipe cleaner through this pipe. The purpose is to drain off any water around the fuel cap so it doesn't go in the tank.