Been across that pass in the Rocky Mt Park. Was on a 97 Goldwing with carbs. It was a little sluggish, but ran ok. It was a different story going up Pikes Peak (14,110 ft). Got almost to the top and had to stop for traffic and almost couldn't get going again. Hardly had enough power to take off, had to slip the clutch and rev really high, no power... but we made it.
For a fun ride try 550 out of Ouray, CO to Silverton then on to Durango. They call it the million dollar highway. You rarely drop below 8,000 ft and are over 10,000 ft in places as well. Great road, only one I have seen that had signs telling you to stay on inside of white line. (There was "nothing" on the outside of the white line, just a sheer drop for a long way. Like I needed a sign to tell me, huh.)
Been back out there several times on the 01 GW with fuel injection and had none of the problems I had with the 97. I would think the fuel management system on the fuel injected scoots like the X500 would not have a problem. I hope to get back out the on the Kymco in the next couple of years. Probably gonna have to retire to have enough time to do so. I've had the scoots down to the Smokey Mts, best altitude is a bit over 6,000 ft. Been all over the Smokeys, but after the Rocky Mts the Smokey Mts are just tall hills. Still al lot of fun on two wheels.