I know that there are probably many other threads out there about how to properly compensate for drastic elevation changes, but im hoping to get some information more im line with my specific setup. So, ive been riding my KLX250 in Pittsburgh PA ever since i got it, and afyer much tweaking over the last year, i had the thing running beautifully. My current setup tharan in Pitt is an FMFPowercore 4 exhaust, airbox lid completely removed, heaer pipe polished a bit, and main jet running a 128. I just moved to Denver, however, (HELL yeah) and i obviously need to compensate for the elevation increase. Pitt is at 1223ft and Denver is at 5431ft... I feel like a dumbass for not understanding this easily, especially because I'm an engineer... but does increased elevation cause the bike to run more lean or more rich?? On the one hand, I instinctively would think it would cause it to run more rich, given the lower oxygen and same carb settings... but on the other hand I feel like what I've previously heard is that it causes it to run more lean, which I honestly can't understand... less oxygen, same fuel delivery via same jet sizes seems to intuitively mean a richer condition. So first of all, I need someone with some more brains to enlighten me on that... and second, given the fact that I was running so well in Pitt at my current settings, what size main jet would everyone recommend I change to, and what else, if anything, should I change? I only have one larger main jet size right now, a 132, and I have plenty of smaller sizes.

Thanks to whoever can shed some light on this for me!

Cheers,
JW