There is nothing wrong with the DR's standard jetting, But the restrictive airbox strangles the power - exactly as everyone has described.
I drilled the EPA brass blanking plug and put in a easily adjustable knurled head mixture screw from Procycle. Im running it at 1 turn out (stock is 0.5 turns) here in Bolivia at the moment (in Canada I run it at 1.5 turns out)
The DR runs very lean without this mod and opening up the airbox transforms the engine at altitude.
I have a Vapor digital dash with thermocouple and the engine temperature barely rises above 100 c with the standard EPA mixture setting and airbox closed.
With the airbox top cut out and 1 turn on the mixture screw, even at 4800 m the bike pulls well ( say 85% of sea level) 2up with loaded HT panniers and the engine temperature is back up where it should be, between 120-140 c - indicating that the combustion is efficient.
If you are riding at elevation and suffering a lack of power, try removing the side cover of your airbox and see how much better it runs. Obviously you need to be running a good clean oiled air filter.
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