Dr650 carb adjustments at altitude
 

Has anyone had to change jets or make other adjustments when running at high altitudes on a DR650. What parts need to be carried please. Thanks

It's all about jetting- a 2 second search with Google finds this PDF document with pics etc which you may find helpful until someone with more knowledge comes along.

Hi DLyttle

Link from Bertrand is good info, but first lets start with a bit more information:
what year is your DR?
what mods have already been done to the bike?
what elevation (where) will you be riding it?

The stock jetting and fuelling is lean on the DR650, but the main issue for running at high altitude is the restrictive stock airbox setup, this can be modified very easily though!

If your DR650 is stock it will have a small 'snorkel' in the top of the airbox, this limits the amount of air getting to the carb.

Most DR650 riders will do 2 things, adjust the jetting/fuelling COMBINED with what is referred to as the 'Airbox Mod' which involves cutting out most of the top of the airbox.

You CANNOT do only one of these mods, they must be done together or you will end up running the engine way too lean (airbox mod only) or running way too rich (jetting carb only)

The best results are if you do both of these mods AND switch from the restrictive stock exhaust to a free flowing exhaust too.

These are solutions to make the DR650 run better - and better at altitude in ascending order of cost:

1) Depending on how high in altitude you intend to go, you could increase the fuel flow by removing the EPA blanking plug on the carb and fitting an extended fuel screw, increase the fuel flow and remove airbox snorkel. At very high altitude you may have to run the bike with the side cover off the airbox and make a slight adjustment to the fuel flow.
Cost $20

2) Jet the carb & do the 'airbox mod' as I mentioned, fit extended fuel screw.
Cost $80

3) Jet the carb, do 'airbox mod', fit extended fuel screw, fit a decent freeflowing exhaust.
Cost ~$400 - depending on exhaust system.

Which ever one you do, first thing to do is to fit a TwinAir filter!

There's also a few other tweaks that can be done to improve the throttle response too. we wont get into that yet!

A lot of guys also fit TM40 pumper carbs - which are $450 and still need the airbox mod and a decent exhaust too.

Pretty much all the information you need for the stock BST carb is here:

The BST-40 Bible - ADVrider

Here's MXRob's website too, he has done just about everything you can do to a DR650, including fuel injection!

http://www.mxrob.com/

Best BST40 jet kit IMO is Procycle's own kit, it has the extended fuel screw, drill bits to remove EPA blanking plug/drill slide, new jets and needle with clip slots and a 'D' spacer, which is much better than using washers as shims with the original needle. It also comes with hex cap bolts to replace the soft screws that the BST40 is held together with.

For any carb work I suggest removing the carb from the bike completely, it is quite quick to do and makes working on it much easier, it is a very simple carb and easy to work on.

My current set up is:
-extended fuel screw set at about 1.5 turns out
-Procycle needle, washer set at 4th clip from top.
-Slide drilled
-150 main jet
-airbox mod done
-Keintech mid pipe with GSXR 1000 Titanium exhaust and FMF USFS spark arrestor fitted
-TwinAir Filter

For all things DR650 look here:

http://www.procycle.us/bikepages/dr650.html

Hope that helps, let me know if you need any more info

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! beer

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! bier

http://patricksphotos.smugmug.com/ph...FVh5qKK-XL.jpg
Imogene Pass, over 13,000 ft. My modified DR ran like crap. Soon sorted however.

Thanks very good info. Bike is 2009 it's in New Zealand but going to Chile soon so I guess around 3000 m in Bolivia etc. it is completely standard. Just concerned that if I do too many mods fuel consumption will increase too much.

our 2009 DR gets between 3.8-4.5 L/100km or 61-75 mpg (imperial gallons), if I keep it around 100 kmh it still gets 75 mpg, up at 110-120kmh down to 60 ish mpg.
That's with the modifications, they have not made a significant difference to fuel consumption, if you fit a TM40 pumper carb it will use more gas.

Highest elevation we got to was 4,800m at Jama pass, the bike ran pretty well, though obviously down on power that high.

It ran well until I got gas at San Pedro de Atacama that had a bunch of water in it :(

If you jet the DR and open the airbox it will run much better - especially for your trip, I wish I had done it earlier :funmeteryes:

Thanks Gipper for the first hand experience. Keep you posted. Rgds

No worries, always good to help out

Mollydog makes some good points there and re side cover captive nuts, easy to lose them!

if you do not do the carb mod, you can also do what a buddy of mine did, which is to enlarge the snorkel hole in airbox and have a flap mounted on a single bolt to the side of hole, so that you can rotate the flap and cover/uncover a varying amount of the air intake, this with the extended fuel screw will give good easy adjustability at up to ~10,000 feet - as Mollydog mentions, as you get up high, if the bike is losing more power pull the side cover off and adjust fuel screw some more.

I wear pretty thin leather road gloves, so I can adjust the extended fuel screw on the move now - it takes a bit of practice but you have lots of time to do that going up the hills in Bolivia and Peru :cool4:

I prefer the Procycle fuel screw which has the flat side on the screw head, much easier to make adjustments and know how many turns out the screw is.