I got my '04 gv250 Sport in January and had been having that problem until about a week ago. Etokar said that his fuel leak was from the line leading out of the petcock, but mine was from the petcock, itself. This is what I did to fix it. This works best if the gas tank is empty or low on fuel.
1) Go to Harbour Freight (or similar hardware supplier) and get a Metric O-Ring set.
2) Remove the front saddle.
3) Remove the 2 bolts securing the gas tank.
4) Turn the petcock to "off".
5) Disconnect the fuel line from the petcock (NO SMOKING!).
6) Gently lift the tank from the stern and disconnect the fuel gauge connector.
7) The object here is to get the relative fuel level in the tank below that of the openening where the petcock bolts to the tank (re:"empty or low on fuel"), but DO NOT remove the tank and turn it up-side down or lift the rear end of the tank so high as to let fuel escape through the fill hole if it were open. The tank lid may leak, and the paint on it is not fuel-proof. If the tank is too full to do this, drain the tank into a gas can or ride the bike until you are nearly into the "reserve" condition. I drained my tank by using a similarly sized four foot length of fuel hose that I had on hand (opening the fuel tank lid speeds the process). I then had a friend hold the tank in that position, but you could probably use a piece of 2x4 or similar support. There is no need to remove the petcock from the tank unless you intend to inspect the fuel filter, etc.
There are two o-rings that I replaced. One is inside the petcock above the bottom cup; the other is behind the ON-OFF-RESERVE selector (on my bike, this is the one that turned out to be leaking). Remove the cup with the approriate wrench (be gentle, the plastic is soft). Use a dental tool or similar hooked tool to remove the o-ring from the petcock and match it to one from the kit. Use a SMALL flat-blade screwdriver and gentle pressure to seat the new o-ring inside the petcock. I coated the o-rings with petoleum jelly. Bearing grease would work, as well. Reinstall the threaded cup. Be careful not to scratch or score the inside of the petcock when removing or installing the o-rings.
9) Holding the fuel selector lever, back out the set screw below the selector until the selector pops out into your hand. Removing the selctor and spring, you will see an o-ring inside. Remove this, match and replace it from the kit in the same manner as before. Reinstall the spring, fuel valve and set screw.
Oh, yeah, reconnect the fuel gauge , lower the rear end of the tank and reinstall the tank bolts and front saddle.
It is probably possible to get just the two o-rings needed from a parts supplier, but I don't know the sizes or part numbers. I opted for the o-ring kit, thinking that I'll need them somewhere down the line.
Hope this helps!
By the way, my leak was more noticeable when the tank had greater pressure in it, for example, a full tank on a hot day.
Bill Ard
Happy Birthday!
