I know some bikes have a fuel off position, but i dont see one on my GS, only prime/reserve/and on. am i missing something, or is there just no off position, and should i allways leave in 'on'?
Thanks,
TT
Yes, always leave it on. The GS has a vacuum actuated petcock. Basically means that a tube connected to the intake opens a valve, so that fuel only flows when the engine is running.
ON and RESERVE use a vacuum from the carb to operate them. PRIME bypasses the vacuum. The vacuum diaphram is what acts as the OFF. Leaving it to ON or RES is fine, leaving it in PRIME may cause engine flooding if your carb float needles do not seat properly.
Also, there is an ON/OFF on the tank petcock. This is normally only used when removing the tank from the bike.