Hello all. I have a 1992 kx500. It has a newer top end, and a stock pipe.
Now to be honest I have never really worked with rejetting a carb. So I am green when it comes to this.
It runs not bad, but does seem to load the spark plug up and then can't get into it's top end until the plug gets clean. It is running really rich. So my question is what jet do I play with. The main jet or the pilot, or both? Also how many turns out of the air/fuel screw do I have to turn? I started at 2 and went to 2.5
I am around 3000ft elevation as well. Hey thanks so much in advance! This place is a major blessing!

I am not sure what you have in the carb now for jets , but , as a general statement , stock jetting is too rich . On my 2003 KX500 , I had to lean both the pilot jet as well as the main jet and the needle for things to work properly . My bike has an FMF Gnarly woods pipe and a Boyesen Rad valve on it and my jetting is 52 pilot at 1 3/4 turns out on the screw and a 165 main . The needle had to be raised to the #2 clip position . In this configuration ( I am at sea level ) , my plug is light brown color ( doesn't matter if I am just cruising slow trails or running hard ) and there is zero spooge out the silencer . Power is very good and 3rd gear power wheelies are as simple as rolling the throttle on . A completely stock bike with stock jetting will be very rich and will never run like it should .

Hey thanks I will start trying some changes

I ride Nevada desert usually around 2000' to about 3500' but have run up to 8000' at MT Charleston without fouling a plug.

55 pilot
168 main
#7 slide
N82M needle

Put the clip and air screw where she runs best.  These settings will get you very close depending on your altitude. Google "Team Green" jetting chart or go to KXRiders.com. A lot of good 500 info over there.

Later