I routinely take my '81 from 1100 foot elevation of Phoenix, up to 6,500 feet on the Mogollon Rim about 100-120 or so miles northeast of Phoenix, and the engine feels like it has lost a good 40% of it's power.
Throw in higher temperatures and high humidity, and you have a quite anemic motorcycle power wise .
Bing has a conversion chart for elevation and temperature different than what the motorcycle is set up for, which is sea level, and 59 F.
What they recommend is going to smaller main jets, which all you have to do is remove the carb float bowl, and unscrew the jets, probably a 20 minute job on the road.