Description of Stock Petcock (frame mounted)

This section describes the operation of the frame-mounted petcock. The GS500 has a second fuel petcock mounted on the underside of the fuel tank. The tank-mounted petcock is not described here.

The stock frame-mounted petcock has three settings: ON, RES, and PRI.

ON is the standard setting that should be used for normal operation. In the ON position, fuel will only flow to the carbs when the engine is running. This prevents fuel flooding in the case of a fuel float valve that is stuck open (when the bike is parked).

RES is used when the fuel in the main tank (ie. the ON position) runs out. The RES setting does not actually draw fuel from a separate gas tank, but rather draws fuel from a lower outlet point in the gas tank. There should be about 1 gallon of extra fuel in the RES position (~50 miles).

PRI is used whenever the bike has been sitting for a long time or if you run the gas tank completely dry. The PRI setting allows for fuel to flow into the carbs even though the engine is off (ie. "priming"). The PRI setting draws fuel from the same outlet as RES. For this reason, running on PRI means that there is no reserve fuel available

Owing to the flat bottom design of the GS500 fuel tank, and empty tank will in fact appear to have a substantial amount of fuel remaining. If the motorcycle sputtered and died out, the best thing to do is fill the fuel tank before further troubleshooting.

This figure may help to explain how the frame-mounted petcock works:

Why Upgrade?

The stock petcock is the culprit for a phenomenon known as fuel starvation. At high speeds, the vacuum-driven fuel line cannot supply the demand from the engine, and the bike sputters as if running low on fuel. Many solve this problem by switching to prime. However, you then lose the reserve tank functionality. The Pingel is an alternative which:

  • keeps reserve/on functionality
  • eliminates vacuum-driven system, so no more fuel starvation
  • vastly improves fuel flow (helpful for racing)
  • eliminates mess of fuel hoses


Parts will cost approximately $120. All installation and ordering details can be found in this thread

2004 - 2007 Petcock

The newer GS500 bikes have a new Petcock design that has overcome many of the flaws of the earlier models that suffered from fuel starvation at high speed. Read and view a disassembled 2004 - 2007 Petcock here.