Fuel Supply Valve

[MasterM3]

Hey guys,

I know this is a really n00b question, but what is the purpose of the fuel supply valve? Can I just leave it on reserve all the time? I don't really understand the concept. I know when switched to reserve, it permits access to a small portion of fuel, but I'm still pretty confused.

Do I just swtich it to reserve when I think I'm low on gas? Will performance be affected? I guess I turn it to off when I'm not riding the bike? And then to On when I ride, then reserve when I'm low on gas?

Thanks for your help guys.

[PitterB4]

OMG - don't run it on reserve all the time - it'll cause an enormous vacuum in your tank that, if you really get on it, will make the tank crush in on itself!  

Sorry - I'm in a bit of a mood today!  

Basically, the "On" and "Reserve" set up is there to help you not get stranded by running out of gas.  There are two straws from the valve into your tank.  "On" sucks gas from the taller one.  Once the level gets below the top of it, you'll start sputtering and seemingly run out of gas.  "Reserve" uses a much shorter straw giving you access to the fuel between the top of it and the top of the "On" straw.  Make sense?

[duane]

the tank crush in on itself!

I laugh, coffee goes up nose, spurts out on keyboard.....

M3, the common name for this valve is petcock.  For some weird reason Suzuki schematics refer to this as fuel cook. (?)

I thought "straws" were a good analogy.

[Red01]

Rob forgot to mention there's no "OFF" position on a Bandit fuel petcock. The 600 & bigger bikes have "ON," "RES" & "PRI" - the 400 has no labelled "PRI" position, but can be modified to have one by removing a screw. In "PRI," fuel flows out no matter what. In the other two positions, fuel will not flow unless there's a vacuum source applied to the petcock's diaphragm, therefore, whenever the engine is not running, the fuel is shut off when it's in the "ON" or "RES" positions.