Honda 125cc - Ignition Timing Adjustment?

Two bikes, same make but different year model, climb a mountainous road,

a) BIKE-A (Honda) - 125cc, Single Cylinder, Capacitor Discharge Ignition (CDI)
b) BIKE-B (Honda) - 125cc, Single Cylinder, Point Ignition

After running for say about 20 minutes, BIKE-A looses its power whereas, BIKE-B maintains its power/speed.

1) Why does BIKE-A looses its power?

2) Does BIKE-A needs retardation for the Ignition Timing?

3) If yes, how do we know, how much retardation is required?

Added (1). The scenario is just an example. It always happens this way.

Added (2). As far as the tests are concerned, even a well tuned CDI bike would fail against a POINT bike. For this particular reason, the natives to mountain areas in my country prefer bikes with POINT. I'm considering to design my own CDI which can adjust the ignition timing in such conditions.

Therefore, I just need help… I.e. Answers to my questions.

Bikes "lose" (note spelling) power for many reasons, including running out of gas, so the question is inherently stupid. How about the fuel system? Filters? Carbs ever been cleaned? Rebuilt? Could be a sticky float valve. Last tuneup? Plugs? Ya gotta timing light, dude? Ya gotta shop manual to follow for an intelligent tuneup, dude?

The timing with a CDI is not adjustable.
The problem is either bike A needs a tune up, or is worn out more than bike B

Variable timing is possible, so is multiple mapping, but is it desirable? Do your customers stick with points because it is more convenient to work on, anyone with a screwdriver and a couple of spanners can adjust their timing, a CDI is not nearly as approachable.

Presumably you would need an oxygen sensor (or perhaps an altimeter) and a load sensor(s).