TWO Fuel Cocks on '80 XS1100G -- WHY?!?

[zatoichi101]

Hi,

I need to preface this question by admitting that I know very little about the mechanical aspects of a motorcycle. I have been riding for decades, and consider myself a fairly good rider -- but when it comes to mechanics (even oil changes), I take the bike straight to the shop.

That said, I have a question regarding the two fuel pet cocks that are just under the tank, on the left and right side of the bike.

I cannot find any information on why there are two cocks. They both have ON, OFF and RES settings, so it isn't like one serves as the reserve.

I have had this bike for a little while, and truthfully, did not notice the right side fuel cock right off. It was in the OFF position. And the bike was riding just fine. When I did realize that there were two fuel cocks, I switched the one (on the right) that I had found to the ON position -- so that both the left and right side were in the on position.

No real difference in performance.

So, if anyone can tell me why there are two fuel cocks, I would appreciate it.

Cheers,

Zato

[fredintoon]

Tapped out?

Hi,

I need to preface this question by admitting that I know very little about the mechanical aspects of a motorcycle. I have been riding for decades, and consider myself a fairly good rider -- but when it comes to mechanics (even oil changes), I take the bike straight to the shop.

That said, I have a question regarding the two fuel pet cocks that are just under the tank, on the left and right side of the bike.

I cannot find any information on why there are two cocks. They both have ON, OFF and RES settings, so it isn't like one serves as the reserve.

I have had this bike for a little while, and truthfully, did not notice the right side fuel cock right off. It was in the OFF position. And the bike was riding just fine. When I did realize that there were two fuel cocks, I switched the one (on the right) that I had found to the ON position -- so that both the left and right side were in the on position.

No real difference in performance.

So, if anyone can tell me why there are two fuel cocks, I would appreciate it.

Cheers,

Zato

Hi Zato and welcome,
your signature says the bike is a G which makes it a 1980 Standard model.
Standard model gas taps don't HAVE an "OFF" position.
They are turned on and off automatically by vacuum lines from the carb manifolds.
They should say ON, RES (for reserve) and PRI (for prime).
The PRI position bypasses the vacuum to turn the gas on without the the engine running.
This will allow the carbs to fill before you crank the engine to get an easier start if the bike has been sitting a while but the gas will stay on once the engine stops so be careful how you use it.
That is, that's what it SHOULD be like unless a PO has messed with it.
And why a tap on each side? OK, it'll run just fine on either one of the taps but if there were only one tap it'd run out of gas sooner because there'd be mebbe a cup or two of gas trapped in the side that didn't have one.
The old Britbike trick of laying the bike on it's side to get that last cupful of gas may work on a 300lb BSA but on a 600lb Yamaha, not so much.

[Ken Talbot]

...That is, that's what it SHOULD be like unless a PO has messed with it. And why a tap on each side? ...

Further, unless it has been messed with, each tap provides fuel to two carbs.

[fredintoon]

Further, unless it has been messed with, each tap provides fuel to two carbs.

Hi Ken,
yeah, I forgot to spell that out. Mind you, Zato claimed the bike ran fine with only one tap turned on.
OTOH the Standard's stock taps are "vacuum on" with ON and RES and "manually on" with PRI
so it don't matter how they are switched, gas can flow through both taps regardless so long as the engine is running.
And if on PRI, even when it ain't.
Which is why I did a K.I.S.S. (messed with) with mine.
Run a gas line from one side to carbs 1 & 2.
Run a gas line from t'other side to carbs 3 & 4.
Pull the vacuum lines and swap each tap lever over to the other tap body.
Now ON becomes OFF, RES becomes ON and PRI becomes RES.
Just gotta remember to turn the taps on and off as appropriate, like grandpa on his Norton.

[mikubuilder]

if you file off that little tab on small cover and file down handle a little bit, pointing UP position is your OFF...JAT