Thom M wrote:
The fuel pump draws fuel from the tank, where with gravity it has to have fuel in the line to work.
In other words the petcock has to allow fuel to drain into the line.
The taller tube on the petcock impedes the gas from entering the line when the tank is low.
By cutting 1/2 in. off the tube you are removing that restriction..

I've read about doing this but I still don't understand how it will help. When I first installed the Grizzly valve I tested it with less than 1/8 tank and the petcock set in the regular position. While riding I realized I was getting low on fuel and the last 5+ miles to the house at highway speeds was with the fuel light on and the guage reading empty. It ran fine.

The standing tube in the tank is of a larger diameter than the carburetor fuel inlet and the gravity pressure in the tube will be the same as it is if the petcock were set in the reserve position.

If the normal petcock position is causing fuel starvation before it normally would I would suspect that the screen is clogging up around the sides. A long hose hooked to the petcock and held above the tank with some carb cleaner in it and a small amount of air pressure to blow it through, with the gas cap removed of course, should clean the screen. If not and a good fuel filter is already in place then I would just remove the screen.

Scott B.