gas tank overflowing

[DimitriT]

The tank on the 550 had a habit of overflowing after a fill up.

I would fill up to the bottom of the filler neck and ride it home. I would park it in the garage and the next morning it would be dripping with gas.

The only explanation I could think of was that the gas was expanding as it warmed up and overflowing the tank.

I tried taking apart and cleaning the gas cap and also tried replacing and reenforcing the gas cap rubber gasket.

All to no avail.

What was interesting was that the 750 never had this problem, even though the gas cap was in worse cosmetic shape.

The bike with the problem did have a sealed/lined tank and the PO who did the job was not especially careful.

One day while filling up the 750 I noticed a small vent hole in the filler neck and it occured to me this hole may be necessary to equalize pressure between the neck and the rest of the tank.

Sure enough, the hole was plugged up on the problem tank. I used a piece of wire to open it back up and clean it out.

So far I have had no overflows during the last two months of the 550.