Good advice above.
A lot depends on how far "into" this you want to get. As mentioned, we need to know if your bike is currently stock or if it's been modified. There is lots you can do ... or you can do very little and still get by. Up to you. The DR650 is flexible!

If totally stock (means: no jetting changes, no washers under needle, no air box mods, snorkel still in place, stock exhaust). If the bike is running well then all you would need to do at very high altitude would be to install an Extended Fuel Screw. (AKA: Fuel/Air mixture screw or Pilot Screw). This is a 30 second adjustment once installed. So Easy. It is blanked OFF on stock Carb, so you'll need to learn how to get to this fuel screw. (not hard ... but, IMO, a MUST DO for travel)

As mentioned, stock DR650 is very lean. This means it can go up fairly high and still run pretty well. Over about 8K to 9K ft. it will lose some power and idle may drop down, may run a bit rough, harder to start. At this point remove snorkel and turn the extended fuel screw IN one half turn, this leans out the overly rich idle mixture a bit. This will help across the rev range, but especially at low RPM, idling and starting.

Then, raise idle up a bit. (1400 RPM is correct) Should run OK ... just remember ALL internal combustion engines lose power at high altitude, no matter the jetting, F.I. or Carb ... they ALL lose power. This adjustment will take you less than one minute to do.

Over about 12,000 ft. I would remove the air box side cover. (make sure to retain captive nuts/bolts) With cover off you should be OK up to 14,000 ft. and even higher. DO lean out Fuel screw further (another one quarter or half turn IN) and raise idle up again if needed.

Replace cover (five minutes to do) when down below 10,000 ft. again,
re-adjust fuel screw and idle once a lower altitude.

There are advantages and disadvantages to running a totally stock set up.
For LD adventure travel, leaving it all stock is not a bad thing. Your MPG will be good, your air filter will remain cleaner for longer and you can easily transition from Sea Level to 14,000 ft. with only minor adjustments that take just a few minutes at most.

Your DR will not have the "Punch" of modified DR's at Sea Level, but will run pretty well even at 13,000 ft. The guys with the modified Carbs and jetting won't be as lucky and will have to do more to get their bikes to run well at high altitude. (over 10,000 ft.)

Good luck!


Imogene Pass, over 13,000 ft. My modified DR ran like crap. Soon sorted however.