New to Vision and motorcycles. What is this switch that says 'FUEL,RES,PRI,ON'?
The fuel petcock has 3 positions: On, Reserve, and Prime.
On is where you should normally have this set. It is vacuum operated and will shut the fuel on and off automatically for you.
Reserve is similar to on, but has a fuel inlet that's lower in the tank. Basically, you drive in "on" until you run out of gas, then you switch to reserve to get to the gas station.
Prime is always on, i.e. not vacuum operated. You would use this to prime a drained carb for the first ride of the season. Since the other two settings are vacuum operated, you'd use this setting for anything that you needed while the bike wasn't running. It's also useful for draining the tank, if you ever have to do that.
The "switch" that you are asking about is the fuel flow control valve. Its proper name is "fuel petcock". Its purpose is to give you control over fuel flow to the carburettors.
Here is a link to the (11J) XZ550RJ Owner's Manual (https://docs.google.com/uc?export=download&id=0B5rMo73UpmHbWnU1dHdvV01BOTg).
It explains this, and other mysteries in excruciating detail.
Thank you, all.
And watch out for "doh" moments with this lever. I have had it set to "reserve" when I thought it was "on". Ran the tank dry without warning and definitely didn't make it to the next gas station.
The trick is to go to "pri" which is horizontal. From there, down for on and up for reserve with the skinny (or short end) end of the lever pointing at the setting you want.
Enjoy.