The dreaded 1980 GS fuel tap...

[Guest]

This is my first experience with the "Prime" only fuel tap. I've just bought a new non-OEM one, and fitted it to my tank. There is an arrow at the top of the "dial".

After putting some fuel in the tank and playing around with the slotted dial thingo and applying vacuum I got fuel to flow.

It appears that:
1. The Prime function allows fuel flow regardless of vacuum when the dial slot is in the vertical position.
2. Turning the dial to the horizontal position allows fuel flow, but only when vacuum is applied.
3. There is no detent or mechanical stop on the tap to prevent rotation of the dial beyond 360 degrees....it can be turned beyond full circle in either direction.

Can anyone confirm that my experiences are as they should be?

Thanks.

[Nessism]

In order for fuel to flow when on prime, a pulse of vacuum is needed to pull open the check valve. The check valves often fail which prevents the prime feature from working. With a new OEM petcock you shouldn't have to worry about that for a while though.

[Guest]

Thanks Ed for the response. I think I'll have to simplify my questions to get a simpler response....

So, should the screwdriver slot on the tap be set to the horizontal position for normal running, and vertical for the Prime function?

[Steve]

Yes, those positions are correct.

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