520 jetting change for colorado trip

[ml36]

in three weeks, i'm going out to colorado for a week of riding. i don't know the exact location of where we are riding, but it is outside of colorado springs. i believe the elevation is around 7-9k.
current settings
ocemn #4
main 165 (alittle on the rich side)
stock pilot
1.5 turns
stock muff

the areas were i normally ride are only about 400 ft in elevation. from what information i have gathered, i should probably only need to lean my main by about 5-8 numbers. hopefully someone who rides in that area can confirm this.

on a side note, i currently have a bad backfiring problem after chopping the throttle. i have adjust the screw all the way from 3/4 to 2 turns and inbetween. i have gone from clip #3 to #7 one step at a time. none of this affected the backfire at all. i have also tried to seal all of the joints with high temp rtv. nothing seems to help. i am going to try leaning the main jet down to 160, but theoretically this should not help, correct? should i also try clip #2? hell, i don't. i'm about ready to give up and not worry about it. the thing is, my buddy has a 400 with ocemn, and it doesn't backfire at all and he doesn't seal his exhaust joints.

later
marc

 

[Anssi]

Originally posted by ml36
in three weeks, i'm going out to colorado for a week of riding. i don't know the exact location of where we are riding, but it is outside of colorado springs. i believe the elevation is around 7-9k.
current settings
ocemn #4
main 165 (alittle on the rich side)
stock pilot
1.5 turns
stock muff

the areas were i normally ride are only about 400 ft in elevation. from what information i have gathered, i should probably only need to lean my main by about 5-8 numbers. hopefully someone who rides in that area can confirm this.

If the temperatures are the same in both areas, you should probably go with a 160 main and also drop the needle one clip position.

 

[tigerowner]

I think Rodzilla has a 520? He rides in the Rampart Range Area.

 

[ml36]

i imagine it will be 20-30 deg cooler out there.

 

[KTMTim]

Your best bet is to contact Jeff Slavens. He is the local KTM & Jetting guru. You can ask him questions through the RMEC website at www.racermec.org Click on AnswerMan to ask your question. I will tell you that you will have to go substantially leaner at this altitude compared to sea level.

 

[ml36]

KTMTim, i did not see a link to AnswerMan.

 

[ml36]

never mind, i just found it at the top of the page. dumars!

 

[marktm520]

I am running the OCEMN in the #3 position and a 160 main. Everything else is stock. At home I ride at sea level and last August I was in Crested Butte Colorado and the bike ran perfectly with the above jetting. We were riding up to 12,900 feet with no problems.

2001 Ktm 520 MXC

 

[ml36]

that's interesting marktm520. maybe i should just have some spare jets and worry about once i'm out there. thanks for the replies.

 

[Rodzilla]

Nope I have the 400 (I'm a pansy! ;) )

If you are riding west of Colo. Springs area then you are looking at the Divide/Woodland park area.

You can get a fabulous map for that area from http://www.thundertrail.com

You need it as all of the trails are marked "717"

Don't forget at this altitude your losing 15-20% of the power you have at sea level right off the bat. I've had guys think the jetting is off and fiddle for a whole weekend, when in reality it's just we ain't got no air! (You'll want to drink a lot of fluids to help combat altitude sickness until you get acclimated)

On my 400 I think the stock jet is a 175 (?) I''m running a 168 now with an EMN in the 5th clip 1.5 turns. I know your 520 will be different but figure 3-4 sizes smaller on the main and lean the needle a bit.

Rod

 

[TexKDX]

The elevation up there is 8800 Plus for Rampart Range and Divide Trail systems.

Drop the main two sizes and lower the needle a clip or two and you should be fine. It would not hurt to have pilots 2 and 3 sizes smaller with you as well.

 

[Strick]

The RFS are not as sensitvie to altitude as the KTM 2-strokes are. I would get it dialed where you are, and bring a couple of extra jets. Cooler Temps = richer jetting, higher altitude = leaner jetting. If it is getting hot where you are now, you are leaning the bike anyway (if it needs it). The cold temps will help your plight, a bit. The main is an easy swap, so it can even be done on the trail.

Good Luck and have fun!