Operating position for the petcock on a suzuki king quad 300?

Answer 1

There are three positions marked on my 99 king quad.

On, Reserve and Prime.

On - is for running the machine normally.

Reserve - is for running when the tank gets low. Gives you time to get back and refill the tank.

Prime - is for priming the carb after the float bowl has been emptied i.e. after storing for the winter or working on the carb.

Note? both the on and reserve positions require a vacuum for gas to flow. i.e. when you start the quad by turning over the engine a vacuum is created in the carb which is piped to the petcock via a rubber hose. This vacuum works on a diaphragm (located in the back of the petcock) to allow gas to flow. I assume this is a safety feature of newer quads / bikes.

If you take off the fuel line and turn the petcock to on or reserve while the engine is off no fuel will come out. However, if you turn it to prime then fuel will come out if the engine is off or on.

Note: I was having trouble with my quad idling and running rich. After extensive pain (rebuilding and resetting my carb a number of times) I eventually found out that the diaphragm in the petcock was leaking gas!

Because I failed to discover this eventually gas actually drained from a full tank of gas into the engine contaminating the oil. Luckily I found out before running the quad but this is certainly something to be aware of.