Probably another stupid question...

You're probably gonna laugh me out of the forum guys but I need to ask the question. New rider, new bike, lack of experience etc...

Here's the fuel tap on my KZ550.



Primary I understand. Reserve I understand. But what the hell is the ON selection for? Go on laugh away, but please explain before you do!

Oh, and can anyone tell me the specific model I have? 8 81 on the handlebars?

Thanks guys.

"Pri"=Prime. This means fuel will always flow into the carburetors until the floats shut off flow. Use this position if you have drained the carbs or the motorcycle has set some length of time to fill the carbs.
"On" is your normal riding position. This means gas flows only when the engine is running so carbs don't overflow if they are not working correctly after the engine is shut off.
"Res" is reserve. Same as on, except used after gas has gotten too low in the tank for "on" to get gas flow, usually 1/2 gallon or so.

you have a vacuum actuated petcock. when the engine is running it causes a vacuum, moving a diaphram in the petcock allowing fuel to flow. If your petcock is working normally and hooked up right you should leave it in the "ON" position. the "PRI" setting is for priming the float bowls on the carbs. Say, if you re-install the carbs on the bike, and you need to fill them with fuel again.

Thanks guys, for the quick response and enlightening me.

spend a couple bucks and get a non vacuum petcock setup.save your self some grief down the road.