petcocks

[jiminos]

Hi, i just looked through the threads and checked with the search option for the forum, didn't find the answer to my question. It is dumb, i admit that up front.... but...
The petcock has four positions off, on, res, pri..... what are they? what is the difference?

see told ya it was dumb.

TIA,

[Snow]

Maybe the specials are different, but my standard has 3 positions: On, Prime, and Reserve.

On- this is your basic on position, controlled by a vacuum diaphram in the petcock that hooks up either directly to a carb manifold or through an "octopus" like on a special. Oddly enough, On is actually the "off" position (and somtimes we might actually refer to the "On" position as the "off" position) - when there is no vacuum holding the petcock diaphram open, the flow of gas is shut off (as long as the petcocks are in proper working order)

Prime-free flow of gas, if you unhook the tank from the gas lines with it on prime, you will have a lot of liquid on your feet.

Reserve - Reserve is the position that is designed to use the last portion of gas in your tank. In the On position (again, on a properly working petcock), the gas flow will stop when it reaches a certain level and when you turn to "reserve", the flow will start again and end when you actually completely run out of gas.

If your petcocks aren't functioning properly, reserve may not work because the On position could actually not stop at the reserve point. Also, if the petcock is in bad shape, "On" may actually be the same thing as prime, thus requiring a rebuild or work around.

Hope I have cleared at least part of your question up

[schpiff]

I have an 81sh..
the "pri" position feeds from the reserve in the tank.(gravity feed from the reserve hole) (if ya run outa gas on prime yer done)
the "on" and "res" positions rely on the engine vaccum to open the diaphram (spider assembly) which allows fuel to flow only when the engine runs. (ideally)
If carbs are "dry" or when in doubt use the "pri position"
BTW the handle itself is the "pointer" on mine..dont know about others. Hope this helps bud..

[jiminos]

thanks snow and shpiff

between the two of you, all my questions were answered, thanx... i appreciate the help.