ofblong wrote:
your ratio also depends on if your in the mountains or not. different ratio if you are in the mountains than at sea level (though the difference escapes me atm).
True. At higher elevations, air is less dense. Your cylinders will pull in the same volume of air that they do at sea level, but the mountain air will contain a lot fewer oxygen molecules by volume. This will cause your mixture to be excessively rich.
This is a common problem in piston powered airplanes that may need to operate from sea level to 15,000 ft. To address it, most have a red knob next to the throttle that controls the mixture. The higher you go, the more you lean.
I wish I had one of those knobs on my bike. It's wheezing and coughing like an old man when it tops a 10 or 11 thousand foot pass in Colorado.
Modern fuel injection systems don't have this problem because they can adjust the mixture when a sensor tells the FI computer that it's getting too rich. There will still be less horsepower due to the lower density air, but you won't also have to deal with an overly rich mixture, fouling plugs and black smoke coming out of the pipes.
