13th Sep 2013, 17:10

I am surprised the author didn't know this, "PRI" stands for PRIME. It allows unrestricted fuel flow into the carb, stopped by the floats. Usually used to fill the bowl if left unridden for a short time. The petcocks that have PRI do not have an "OFF" position, they have ON and RES (reserve), which are both closed when the engine is off, and opened when the engine is on, operated by engine vacuum. So on this bike, "ON" (or RES) is the appropriate position when the motor is off, but PRI is not as it will not stop fuel flow ever, and you may end up with flooded carbs and a fuel puddle on the ground.

13th Sep 2013, 17:12

I should also add that if a petcock does not have PRI, it should be ON, OFF, RES.