gas tank switch ?

[spec]

any one know about this? once again
it's my first bike and ive only had it a month or so.
my tank switch or whatever it's called has three
settings on the top it says fuel. on the right it says pri. on the bottom it says on. and on the left it says res. now i've always left it on on. but my friend told me it was bad for the carbs to leave it on unless i have a fuel pump ... i don't know if i do ... but there's no off what should i do ? i'm pretty sure res. is reserve ? 82 gs 450 t spec

[Norseman]

Spec,

The "tank switch" is called a petcock, and on your bike it operates based on vacuum. There are three positions, as you already discovered; "On", "Prime" (Pri), and "Reserve" (Res). Prime is unrestricted open, and is basically intended to prime the engine or pre-load the fuel system. "On" is the normal position, and gas flows when a vacuum is introduced (from the engine). "Reserve" is obviously there to get you to a gas station should you ever run out of gas (not that this has ever happened to me ).

I'm sure your friend is thinking about non-vacuum petcocks, and sure, you should never park the bike with a fuel valve open (gravity, you know). But since your petcock is vacuum-controlled, you don't need to worry about it (other than don't leave it in the Prime position).

I hope this answered your question.

Norseman

[spec]

thank you

thanks for taking the time
this site has been a great help thank you

[Zooks]

In Australia we call it a petrol tap.

My 'pet cock' is tucked away in my trousers.

[RIFLEMAN]

In Australia we call it a petrol tap.

My 'pet cock' is tucked away in my trousers.

ROTFLMFAO!!!!!! Not a very mindful pet,is it?

[Redman]

Your friend is kinda right and kinda wrong.

It would be bad to leave it in the "ON" position if the only other position was "OFF". SOme other motorcycles have only ON - OFF.

WHat others have said about RES-ON-PRI are correct.
I think the "ON" would be better described as "AUTO" in that it automatically opens (by engine intake vacuum) ON when the engine is runing and automatically closes OFF when the engine is not running.

Your friend would have been more correct to tell you not to leave it in the PRI position. The PRI position on yours is more like the ON position of those that have only ON-OFF.

[bwringer]

PETCOCK! Say it loud, say it proud. Now that we finally have forum software that doesn't change it to pet****, we don't have to wimp out with "fuel valve" or other sissy euphemisms.

Anyway, they only last about 20 - 25 years, so if yours hasn't ever been replaced, you might need to think about it. They're about $40-$60 depending on the model. The rebuild kits are junk -- buy a new one if you need it.

The vacuum diaphragm is usually the first thing to go, and it starts leaking tiny amounts of fuel into one carburetor through the vacuum line. If you're fouling one plug, the petcock is usually the problem.

The descriptions above are correct -- leave it in "ON" position, and it should not flow fuel unless the engine is running and applying vacuum.

If the engine is off, ON is OFF. If the engine is on, ON is ON. PRIME is always ON -- don't leave it on PRIME more than a minute or two when needed. Got all that? \\/

For example, if you need to remove the tank, turn the engine off (duh) and make sure the petcock is set to "ON".