Using the gearbox, and keeping the engine RPM's in the power band, are key to operating this bike at high altitude. I've clocked 4000 miles (6437km) on my bike since mid April, all at altitudes ranging from 6500 to over 10,000 feet above sea level. I've had no problem passing cars going uphill at these altitudes, even on fairly short straights between switchbacks. Like I said, it's all about working the gearbox, and staying in the power band (7000 to 10,000 RPM). I've even had my bike to a top speed of 96 mph on a long, flat stretch of two lane road, which was at about 6800 Ft. above sea level. Not too shabby for this bike, IMO.
EYVoom, how is the condition of the road from Minturn to Leadville? I haven't been up there in years, but as I recall there are some pretty nice turns on it. Last time I rode it, I did a big loop, from Avon to Leadville, over to Independence Pass, down into Aspen, then on to Glenwood Springs and back to Avon. A long, but fun ride.
Oh yeah! I plan on heading out that way in 30 min or so. There was a sink hole on Tennessee pass earlier in the summer, but they've finally gotten that all taken care of. I certainly make due up here (working the gears and what not), I just wish I knew how it would perform at full HP.
If I had to live in a higher elevation area, long-term, the CBR250 (as much as I love it) would not be my first choice for a bike. For me, even at sea level it would already be as low as I prefer going, as far as power goes.
I see two ways around this problem. 1) put it out of your mind and enjoy what you have with the 250, or 2) trade it up for something with some more kick to make up for the loss in power you're experiencing that high up. If you like sport bikes, sit tight for a few months and go for the new 500r.
Dang, I live at sea level in CA, and all I dream about is when I'll get the chance to pack it up and get the CBR over to Independence Pass! There's just something very attractive to me in the thought of flogging the CBR250 over a high-elevation pass in first gear at WOT... with other cars passing me! I think it might be a different experience than when I ride my CX650 Turbo over Independence Pass!