> From: "Berger, Michael J" <MBerger@xxxxxxxxxxx>
> I noticed on the petcock that there's the typical "on" and "res"
> settings, but there's also a "prime" setting. . . .
Your petcock is vacuum actuated. That is, while your
engine is running, a vacuum sourced from the rear
intake manifold holds the petcock open. As soon as
you turn your bike off, the petcock closes.
It has 3 positions. Run, Reserve, and Prime.
The Run and Reserve positions function the same as
a manual petcock except that they both close off the
fuel flow automatically if the engine is not running.
Consequently, you never have to remember to turn
your fuel off.
The Prime position allows you to bypass the vacuum
actuated Run and Reserve functions and flows fuel to
the carburators even when the engine is not running.
You'd use the Prime position to start your bike
after it's been sitting around for a long time and
the gas has evaporated out of your carbs. This would
be necessary because you'd never generate enough
vacuum to open the petcock while cranking the engine
with the starter, so if the carbs are low or dry, your
bike would never start.
I don't know if the Prime position draws its fuel from
the Run tube or the Reserve tube, but I'll bet it's from
the Reserve tube.
Regards, Gary in Sandy Eggo
___________________________________________________________________________
(un)subscribe info, archive: http://archives.itg.uiuc.edu/virago/
