The carburetor consists of four components:

Pilot Jet - this controls the amount of fuel when idling
Main Jet - this controls the fuel when you open up the throttle (between 50 and 100 percent power)
Jet Needle - this controls the fuel when you open and close the throttle (between 20 and 80 percent power)
Needle Jet - this is what the jet needle pops in and out of (between 15 to 60 percent of throttle
As you can see the carburetor consists of several parts that work, sometimes in unison, to influence the mixture of fuel and air.

Jetting Your Dirt Bike
This is where it gets easy but tricky at the same time. If you're running rich, for example, you'll need to check the main jet, jet needle and needle jet. However, you only need to tinker with the main jet and if that solves the problem you found the easy solution. If it doesn't solve the problem, then you?ll need to check the jet needle and then the needle jet.

Don't mess with all three jets at once. Change the main jet first and see if that solves the problem. If it doesn't, you'll need to reestablish the main jet to its original position and then move on to the jet needle and so on.

I've made several trips that involved days spent over 4000 meters, bikes ran like shit, but made it through. If you're constantly making trips up into the mountains, you should sort this out as soon as possible. One of the big problems you're going to run into is the fact that most Chinese carbs don't have numbered jets in them and it's really hard to get an assortment of jets for some carbs.