High altitude modifications? DR650
 

hey all

planning on the salt flats in bolivia and some other extreme high altitude rides i will elaborate on later (over 5500m). Will the carb need rejetting? or is there any other modifications that i could possibly do to the bike

DR650SE 2006.

:-)

The standard mods are to take the air filter out (obvious downsides to this!!) and re-jet the carbs. This isn't a big job but I haven't found a way to accurately predict what size to go to in order to adjust for altitude but you need to go down in size (less oxygen is available so less fuel required).

I guess in theory adding a supercharger or nitrous would also help but re-jetting the carbs would probably be easier!

Your bike *needs* nothing, although some would disagree. Rejetting is common, but don't neglect to change jets back to larger sizes before descending or you may do major damage. Some do things to increase airflow, including but not limited to what henryuk mentions (which I'd not recommend on dusty altiplano roads).

I rode a carburated bike from high (4000-5000 meters) to low, then back up to high altitude repeatedly in transiting Peru, Bolivia, Chile and Argentina. Never changed jets and never opened anything for better airflow. No damage to bike, no time spend fussing with carburator parts. Lost a lot of power and had to slow down sometimes.

Hope that's applicable.

Mark

ok thanks people.

i was more leaning towards marks solution... do nothing. i did this through india up to 4500m and it was fine, although a massive loss in power of course.

Sometimes the shop manual for the bike (the genuine factory dealer service manual) will contain a useful "fish hook" tuning graphic. It will give jetting advice for both temp and altitude. The problem is that if you are jetting for altitude it is for use at that altitude and will not be worth it if you are just going up and coming down, if so, you would be doing a lot of jetting changes.

Keep the bike simple and you won't have problems. We have 2 x DR650's and are currently in Peru. No issues thus far.
Daryll

I rode my KLR through Bolivia while it was jetted for the sea level. You lose a gear's worth of power but you get by. Just remember about the lack of power when you're over taking traffic and a bus is coming at you...

Agreed, carburated bikes dont need tuning and big cylenders have enough power to afford some loss of power, you rarely exceed 80 km/h on mountain gravel roads.

I m in bolivia on a 600 xte and never experienced any problem so far.

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.