Commando petcock

One petcock has a stand pipe. That is the one normally used. The petcock without the stand pipe is the reserve. Some folks rely on the center hump but it doesn't leave you much in the way of reserve capacity.

Alan L said:

Hi all,
does one of the standard taps on a Roadster have a stand pipe in it to provide the reserve or is the reserve fuel provided when the level in the tank is sufficiently low that it cannot flow from one side to the other, because of the internal hump in the tank where it fits over the frame.
I hope this makes sense
al

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On my rider I have two "reserve petcocks" and I only turn on one side. When that side runs dry there's still gas in the other side. However, it you use two reserves and turn them both on both will go dry at basically the same time. For customers I install one main and one reserve but then the gas in the bottom of the main side is never used - can be confusing.

Thank you, you have answered my question.
That is basically what I thought was the case.
Because of the very small capacity of the roadster tank I didn’t like the idea of any unusable fuel.
I removed the standpipe from mine so all fuel should be available . I asked the question as I didn’t know if the taps were original. I think I might have Trident ones on my bike. The T160 does need a standpipe because of the shape of the tank.
Did Norton taps have the backing plate behind the lever annotated ‘reserve’ etc. I notice some taps don’t seem to have them?

Alan L said:

Because of the very small capacity of the roadster tank I didn’t like the idea of any unusable fuel.

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Not completely unusable as the bike can be leaned over until the fuel trapped on the main tap side sloshes over to the reserve side of the tank which gets you another five miles or so.

Alan L said:

Did Norton taps have the backing plate behind the lever annotated ‘reserve’ etc. I notice some taps don’t seem to have them?

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From the 850 Mk3 and T160 etc. RES on the left-hand side and the lever turned upward for on (T160 below) although that type is no longer available.
Another US Federal requirement I believe.

I try not to use reserve at all because it is exposed to more dregs than the standpipe side.
Jaydee