My experience with fuel starvation by petcock was similar. Trying to maintain 65mph against a 20 mph headwind. The bike would act like it was running out of gas. As the bike was slowing down, I flipped to PRIME while still moving and it brought immediate relief.

I determined that I had a stiff petcock diaphragm that would not hold the petcock open during low carb vacuum conditions.

There is no problem at all running with the petcock on PRIME. The only issue is the lack of a fuel reserve, which means you need to really keep track of miles since last fill-up or as you mentioned, carrying a small amount of gasoline in a separate container.

Edit: no need to cap off the vacuum line in this scenario. The vacuum line is not leaking. There is still vacuum there, but just not enough to hold the diaphragm open.

I stopped reading when your “ mechanically inclined” friends suggested that the wires flew off due to wind blast.

Don’t ask for their help anymore.

Say what?

Using PRI to get back home is a good plan - but I would not count on it for a permanent fix.

The stiff diaphragm may begin to leak fuel into the vacuum side any day now......and/or maybe start to decompose and flow pieces down the fuel line into the carb.

Now that you know what the problem is, it is time to fix it with a new diaphragm or a Raptor petcock.