High elevation jetting for 220

[DirtRoller]

I'm going to high elevation next week.
My bike is stock except for the air box lid is removed.
I have been up to 5000ft with the stock jetting and didn't have any problems.
Now I will be riding at 7000 to 10000,and I'll have to say the temp will be around 70 to 80 degrees.
I am not looking to race the bike just looking to keep it from fouling a plug.
So if you have ridden at this elevation and had to rejet to do so. Can you tell me what worked for you?
I can only get main jets before I leave. The others I would have to order.

 

[Jason02R]

a 42-45 pilot and a 150 main jet with the needle in the 1-2 slot from the top works best for me but I ride a 200, don't know if a 220 would require something else. but I ride anywhere from 8000-12000

 

[Colorado Mike]

I've got an '04 220 and have a 40 pilot in now with the needle clip in the top position, and I think I'm 2 sizes down from the stock main, sorry, don't recall what that is. My bike has an FMF gnarley woods pipe, no top on the airbox and the stock silencer. I ride at 9,000-13,000', and right now I've got a little bit of a bog just over idle to about 1/8 throttle, then it pretty much rips. I'm going to try lowering the needle clip one notch. I had tried a 38 pilot, but that was too lean, and I couldn't adjust the airscrew properly. Someday I'll have to take my bike down to sea level, jet it, and see how much power it has once it gets real air.
Good luck, and drink lots of water when you're at altitude.
Mike.

 

[skipro3]

Go to http://justkdx.dirtrider.net/
Click on "KDX Tech Tips" located on the left.
Click on "Carb tuning" located under the Engine heading
Scroll about 3/4 of the way down. You will find a Jetting Correction Table that will tell you what your jetting size should change to for elevation changes.

For example: a 148 main jet at sea level would need to be factored by .92 for 82 degreess air temp at 10,000 ft elevation. New jet size would be 148 x .92 = 136.

Good Luck,
Jerry

 

[DirtRoller]

Go to http://justkdx.dirtrider.net/
Click on "KDX Tech Tips" located on the left.
Click on "Carb tuning" located under the Engine heading
Scroll about 3/4 of the way down. You will find a Jetting Correction Table that will tell you what your jetting size should change to for elevation changes.

For example: a 148 main jet at sea level would need to be factored by .92 for 82 degreess air temp at 10,000 ft elevation. New jet size would be 148 x .92 = 136.

Good Luck,
Jerry

Thanks Jerry (for formula). I looked for this but did not see it. Guess I gave up halfway down the page :think:
I think I'm going to drop dwn. 1 size on the main and call it good. I'll bring a few extra plugs just in case.

Thanx for the help with what you run Jason, Mike.
Hydrate, Hydrate, Hydrate... this will be my mantra.

 

[skipro3]

Riding that high and at that warm of a temperature, you won't have any problem dropping one jet size. Most likely the conditions would allow for 3 or 4 jet sizes. Start with one and take the next couple along with you. It doesn't take but about 10 minutes tops to swap a jet out. Keep a few extra plugs in case you do foul out from being too rich. Good mantra too. Your bod will thank you for it during and later. Carb up and remember, if the bike has trouble breathing so will you. The tasks that seemed easy at low elevations will have you sucking hard at the heights your talking about going to.

 

[DirtRoller]

Jerry, I see you live in Lake Tahoe area. You lucky Dog!
I've done a bunch of mntbiking up there, but have not done any biking with a motor yet.
Back to the jetting thingy. I have a 145 main in there now and I'm droping down to a 135.
I think this should be in the ball park. What do you think?

 

[skipro3]

That's a span of 4 sizes. If you are jetted correctly at sealevel with that 145, then...maybe. But if that is from a correctly jetted elevation of 5000 and heading up to 10,000 then it could be too much. Just remember that it's easier to swap a jet out then to recover from a lean seize. With that said, I've jetted down to 140 while riding at around 6,000 ft and higher, and run a 145 from sea level to 6,000 ft. The rest is adjusted with my airstryker air screw for best performance. I don't think they make a jet down to 135. Jet sizes available that I am aware of are as follows:
140,142,145,148,150,152,155,158,160,162,165,168,170,172,175,178,180
Notice the cadence of the jet sizes. From fattest to leanest: 2,3,3,2,2,3,3,2,2,3,3,2,2, etc.
Let me know if you have a source for jets down to 135.

 

[DirtRoller]

Just pulled the plug and it was a little black...the bike seem to run fine though.
That was a 145 main @ 3000 to 5000 on a very hot day(90+) with no humidity.
I have a 135 main it came out of a keihin jet box, so I am assuming it is for my carb. Went and bought a 140 today and will start there. Now that I have 2 extra plugs.
Thanx again.

 

[skipro3]

You should be good to go! Let us know how the ride went and how the bike performed for you.
Remember, overall color only will tell you the plug is of the correct heat range, not your air / fuel mix correctness. For that you need to read the ring at the base of the insulator after a proper WOT plug chop.

 

[bereal]

High Altitude Jetting

I run a 140 main, 40 pilot and the needle dropped one position. This is on a 2000 220 that has a gnarly pipe , turbine core 2 silencer, pro series reeds, and the top of the air box off. It works well up to 10,500 where I ride in AZ. You might try a 138 main but the 140 seems to work pretty well.

Eric

 

[skipro3]

Bereal:
You say you run a 140 up to 10.5K elev. What is the low elevation you run that jet at, if you don't mind my asking?

 

[bereal]

Jetting

I run the same jetting during the summer near Phoenix. The altitude in the deserts outside of town starts at around 1500ft and goes up from there. I dide a night ride last week where the temps where in the 90's and I went from 1500ft to 6000ft during the ride and it didn't seem too lean.

Eric

 

[DirtRoller]

I'm back and here is what I found.
My bike is stock with just the top off the air box.
The only thing I change for this trip was the main jet. (From 145 to 140)
Average riding elevation was 8600ft. The bike had a bog in the low rpms or when lugging the bike. It never stalled though.
Once you got the revs up it ran fine.
Pulled the plug and it was a nice tan color all the way down the porcelain.
I'll post a link to the trail pictures as soon as I get some time and some rest.
Thanks for all the suggestions,
Fred
P.S. I love water XXX's :)