Getting to the top end of your motor to access the carb, plug or cables is a pain in the butt if you need to do it fast in between race.  The major object in you way is the fuel tank, which actually removes quite easily, but is kind of a pain if its full of fuel.  You have to remove the fuel valve and disconnect the hose, or remove the hose, and plug it off, and anyone who's done it will tell you a load of race fuel in your shoe on a hot day is no fun.

Here's simple, inexpensive modification I did using a variation of a standard disconnect  valve.
Since I assemble these valves from components, I decided on a  5/16" valve with a 90 degree end with no valve, allowing for a more compact installation.  The valves themselves actually have a 3/8" OD, which makes for a tight connection to a piece of 5/16" Motion Pro Tygon hose.  No need for a clamp, and a clean square cut on the hose butts up nicely to the flange.  The valve doesn't impede the fuel flow at all.

After re-fitting the clamp on the fuel tank and a bit of trimming the line to the right length, we came out with a neat installation that clears the radiator, hoses, cables and frame.  Now to remove the tank, you only have to push the button, and the valve stops the flow from the tank.  Easy.  The valve also makes a solid "click" when pushed back together, and the 90 degree end is easily swiveled the right way, so you don't get a kinked line.  Quick & easy.