Carb jetting

Hi Muckybill,
Air has a weight factor(14.7 lbs/sq in at sea level) and gravity affects the weight of the air. The weight and density of air decreases exponentially as you move away from the earth.
When you ride your bike up into higher and higher altitudes it runs richer and richer as you climb.The jet sizes provide the same fuel flow but the air is thinner and the fuel air ratio lower.As a result of this you must install smaller carb jets to match the thinner air as you climb.
As temp and humidity also effect the air density it becomes more complicated .It is very difficult for anyone to determine what jetting you should be using anywhere in the world without some firsthand data.
I would suggest that you you take some main jets with a size - 20%( plus and minus 5%) the stock jetting.

Muckybill, for an example of jetting changes, get your hands on an owners manual for a Honda CRF450R. It has an excellent section in it concerning the FCR carb, which every motorbike with an FCR should have. In this section is a jetting graph with altitude as one axis, and temp as the other, giving you jetting for each condition. Now, the Honda will have different initial jetting than your bike, but the increments in main jet, pilot jet, and needle position change per condition change will give you an idea of the change you may be needing to make, and while not absolutely accurate, it's a good start for a wild *** guess. In this graph, it suggests going down two steps on the main, one on the pilot, and dropping the needle one step, for the altitude change you are looking at. Hope this helps.