The idle fuel mixture screw does not have any affect on how the engine runs at anything over 1/4 throttle......it will supply no fuel/air mix at highway speeds.

As the diagram below shows, the fuel mixture screw is a "fine tuning" adjustment.....a larger amount of fuel/air from the pilot circuit bypasses the screw and goes directly to the small holes cut into the side of the throttle body.  (This is why the engine can continue to run well if you have a pilot jet that is too large.....the fuel/air adjustment screw can be completely closed, as the engine gets enough fuel/air without any coming through the closed screw).

Also - the fuel/air coming out of the small holes only has adequate vacuum when the throttle butterfly concentrates the air flow across the small "transfer ports" that are drilled into the side of the throttle body for the fuel/air mix.  The location and size of the holes determines the amount of fuel/air mix that is added to the air flow as the throttle butterfly opens....once the butterfly is open about 1/4 the flow is not concentrated across the ports....and there is not enough vacuum acting directly on the ports....and the pilot circuit ceases to operate.

Do you still have the stock vacuum operated petcock on the bike?

The diaphragm can get stiff and restrict fuel flow at high throttle settings  (low engine vacuum)......or the diaphragm can get holes and allow fuel to flow through the vacuum line and result in the engine running too rich.

batman wrote on 09/10/19 at 07:49:40:

Dave, Each stage of the throttle opening controls the speed of the motor ,but nothing stops the pilot jet from flowing even at WOT ,it may feed less fuel over all, due to the drop in vacuum as the throttle plate opens , but there's never a time that the vacuum  drops to zero , nor is there a controlling devise that would close the circuit,  like that found in the TEV valve .

I'm not sure that's true. During times of high fuel flow the level in the float bowl drops, at this point the pilot jet is unable to extract fuel from the bowl and the needle, then the main become the only means of fueling.

Dave ,I looked at the site you posted , it said that as the throttle opens the fuel is pulled through the opening  without the fuel screw , but doesn't state anything about the flow stopping.Dave you have the means to test, you have an O2 meter , use your 50 pilot ,and test at 4000-5000rpm , replace the pilot with a 60 and retest ,if the O2 stays the same then your right .

Gary , If the float bowl level dropped ,Then I'd have to think WOT would be a limited time process. If the float valve is large enough to provide the main jet at WOT , I'm sure if the float level is set right it will also provide fuel to the pilot jet

Dave , what I objected to was that you said the pilot jet ceases to operate when the throttle opens wider than 1/4 , nothing else. there is always a  vacuum on the intake manifold when the piston moves down ,and 14.7 psi at the mouth of the carb and nothing in the pilot circuit that would stop the flow of fuel . The stock carb is a CV after all .Some  research on your part would show that the pilot jet still supplies a small amount of fuel even at WOT.