Jetting Woe's... 2001 KDX 220R

MattTB · Dec 9, 2001

Hey, all,

I'm hoping you can help me out with a jetting problem... This is myfirst (2001) KDX-220-R and have a major jetting problem. I bought the bike used and here are the specs:

FMF Gnarly pipe; Air-box lid removed; Yamalube R-1 premix at 40:1 (93 Octane gas); Twin-Air filter with Bel-Ray element oil (gum!); stock Khein carb; NGK BR8ES. I live in Central Florida, so the humidity is always above 60% (up to 95% is common) and the elevation is basically sea level.

Any ideas on an "ideal" jetting for this bike with the specs above? I bought the bike used and the previous owner said the dealer he got it from jetted it for the pipe it has, etc... Well, it loads up BIG time if you are not getting on the bike most of the time. I do a great deal of low speed (off-power band) riding at times when setting up enduro trail and simply cannot have the bike choking and fouling a plug after 5 minutes... you know?! I know I'm not being a "good investigator" by asking for a magic jetting formula, but I was asking in hopes someone would have an ideal setting before I spend money on lots of pilot/main jets and make myself crazier than I am! :) Also, I do ride the bike rather hard from time to time, so I need to figure that into the jetting formula so I don't seize it while beating on it. I have not checked the jetting sizes yet... I was hoping to get the numbers first, then dig into the carb and see what it's set up at.

Many thanks for any info or direction in advance. Maybe someone out there has the "magic" jetting formula? :)

Matt J.
p.s. - My last bike was a 1987 KX125 that NEVER fouled a plug no matter how long it was riden at near idle speed... I'm hoping for the same thing with the KDX!

atc3434` · Dec 10, 2001

Well, that perfect jetting is possible, the KDX220 I've been riding didn't foul a plug the whole year, even with a lot of barely off idle riding. I'm not sure on close jetting for you (I'm in NY) but you just gotta experiement till you get it right some times. Best of luck.

TMDirtDad · Dec 10, 2001

KDX jetting

MattTB;
Ihave the same bike w/ these mods: FMF Gnarly, TC2 silencer, Boyesen reeds, airbox lid on, (snorkel out) premix is SuperM @ 32:1. Just put a BR8EG
plug in which I think is better. Pilot is at 38, main is 140. I'm just trying to get a clean, smooth running bike right from idle with no skipping (kinda like a 4 stroke!) Then I will be in KDX heaven! I'm looking into changing the needle next. But in answer to your question, try my setup. It really runs pretty good once you get past low throttle position. Try airbox lid on and off, see which you like best. Good luck!

P.S.- Seriously consider having an MX Tech associate re-do the suspension. You will not believe the difference. It was the best $$ spent on the bike.

MattTB · Dec 10, 2001

More info...

I also have the TC silencer and have Gold valves up front and in the rear shock. I will just try some smaller pilots and maybe running the #8 plug you recommended. Also, the suspension is KILLER in rough stuff (roots/major breaking bumps), but it terrifies me in BIG whoops. I think the front end is too soft since the rear end is kicking way too high and the settings are almost full soft on both adjusters for the rear shock. Any more info appreciated!

Thanks again,

Matt
p.s. - The suspension on the poor old (beat) KX-125 was SO good I could pin it in 4th gear in almost any sized whoop and NEVER ever worry about going over the bars. The KDX feels good in most cases, but coming into whoops fast I think it only wants to buck me over the bars something fierce. Time to re-adjust.
p.s.s. - I really like this bike (and it's power when not loading up), but just need to get the fine tuning taken care of.

Fred T · Dec 10, 2001

I'll take a crack at this...

first of all what do you have in the bike for jetting? Try turning the air screw out up to 2 turns, it that still seems rich you need a smaller pilot.(stock is a 42) Place clip on needle in #2 and run a 145 main jet. If that seems rich move the needle to #1 next. If that seems too rich try a 142 main and put the needle back to #2 clip position. If you run a 142 you better do a WFO plug chop to make sure it's not too lean.

Regarding your suspension. Try clicking the forks firmer (IN) 2 clicks
Try clicking the shock firmer (IN) 2 clicks top and botton. BIgger hits require more dampening and more compression. If that was too much try backing off 1 click on them, if it was better but not good enough yet keep going in 1 click at a time until it handles the whoops better but still feels good in the smaller stuff too. At some point one shock clicker may have to quit while another one still may need more adjustment. Click on the MX tech site to the left and read their tuning guide for better info on getting it right and avoid "packing", but I suspect that Fla has the same big honkin whoops we get here in MI due to the sandy soil.

TMDirtDad · Dec 10, 2001

Matt;

After getting some response to my question"How do I make my KDX run smooth?" I'm going to return to stock jetting (42 pilot, 145 main, clip on 3rd) and start over with airscrew adjustments to try and figure which direction to take. Good luck- you learn a LOT as you explore.

My suspension was out of balance like yours-soft in the front, hard in the back. I had to change shock spring to suit my weight (which ain't heavy!) the clickers wouldn't do it.

Jetting Woe's... 2001 KDX 220R

MattTB

atc3434`

TMDirtDad

MattTB

Fred T

TMDirtDad

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