I participated in implementing a mod to the Space Shuttle many years ago involving tire pressure transducers and temperature sensors on each wheel.
I recall observing that as the orbiter ascended from sea level to orbit that the tire pressure indications would always
increase by 14.7 psia due to the elimination of the surrounding ambient air pressure.
Therefore, as you ride your motorcycle to a higher elevation, tire pressure
increases somewhat due to the decrease in the outside air pressure. This
increase is so miniscule as to be lost in the noise!
More noticeable is the change in
temperature due to an increase in elevation. Ambient air temperature generally
decreases by 4 degF per 1000 ft of elevation. This change in ambient air temperature will likely have more effect on
decreasing tire pressure than outside air pressure increasing it, but it too is so miniscule as to be insignificant.
In summary: once you are rolling and your tires are working, the actual tire pressure should not vary by more than +/- 1 psi from what you put in to it.
Truthfully, I'm just pulling the summary out of my ***, but that's my opinion and it makes sense to me. Thanks for asking!