I just made a nice improvement to my custom fuel tank.
This fuel tank setup has proved very dependable since first putting it in service 2 years ago, but one slightly annoying problem that it shares with even the stock fuel tank, is that when it's filled to the top, you get a slight amount of leakage through the vent hole in the cap.
The solution I've come up with, I got got from seeing how my chain saw solved the same problem.
What you're looking at here is a short piece of stainless steel tubing inserted into the hole in the cap that formerly served as the vent. The hole it sized so that the steel tube is a tight fit. It's jammed into the hole, and then I used some plastic fuel line that I bought at the hardware store to fit over the steel tube. Then I used a heat gun to make the fuel line hot, almost to the melting point. Then while still hot, I used a pair of needle nose pliers to squeeze the end of the plastic fuel line closed. All you have to do after that is use a very small screwdriver to insert into the line to make sure it's not welded shut.
The first time I opened the plastic line back up it didn't want to stay closed all the way, so I repeated the heating process a second time, slightly higher up the tube. After that, even after slipping the screwdriver into the line, it stayed closed all the way when I removed the screwdriver.
Now it acts as a one way valve, allowing air into the bottle as the fuel level drops, but doesn't allow fuel to splash out of the vent hole, and drip on my rear fender when the tank is full.
