Tight woods jetting recommendation for 02 KX250

S

scotth

~SPONSOR~

Sep 17, 2001

46

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• Jun 14, 2002

• #1

Bike is stock with stock jetting, 55 pilot, 165 Main, and NAFF #2. Altitude is about 400’ and temps average about 88.
Judging from how fast the bike loaded up in tight trial conditions (First and second gear stuff with no place to open it up) I think the bike is way to rich. The plugs are black within 15 minutes of riding in these conditions.:eek: I no I am going to have to get smaller jets and possibly even a leaner needle. Do any of you have a good starting point? My first attempt would be to go down one size on the pilot and put the needle clip in the #1 position. I thought it best to try and get some input before I start. :think:

Thanks
Scott

 

Last edited: Jun 14, 2002

C

CylinderStay

Member

May 18, 2001

95

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• Jun 14, 2002

• #2

I found my '02 KX250 was rich from the factory (The stock main jet is actually a 165. Maybe your dealer changed it). When I rode it for the first time it sputtered at low revs, hit pretty good mid-range, and then sputtered at high Rpm's.

So what I did was go to a 162 main, kept the stock needle, but moved it to the first position, then backed out the air screw a 1/4 turn. It ran MUCH better then.

I too ride the woods and trails, so I spend a lot of time in 2nd and 3rd. It still seems a little rich at low RPM's so I'm going to drop the pilot down to a 52 and play with the clip and airscrew positions.

You really should do a complete plug check (at 1/4, 1/2, 3/4 throttle and WFO). That will be the only way you will know what it's doing. I hope my experience gives you some ideas but still, do the plug check. You might want to post in the "Mods and Performance Forum" There are some good people over there that can really help you. Good luck.

P.S. Also check the jetting links at the top of this forum! :aj:

 

Last edited: Jun 14, 2002

S

scotth

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Sep 17, 2001

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• Jun 14, 2002

• Thread starter
• #3

Thanks CylinderStay for your input, I am going to try the 52 pilot and the needle in the first position tomorrow. I don't have a smaller main, so that will have to wait (It seems you have to order everything. No one stocks anything around here :( ). I have read some other posts and a hotter plug might be required for my slower riding conditions. Has anyone ran the BR7EIX plug with better luck?

Thanks
Scott

 

Last edited: Jun 14, 2002

C

CylinderStay

Member

May 18, 2001

95

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• Jun 14, 2002

• #4

By the way, you don't need to use those expensive "Iridium" plugs. Your bike should run just fine with standard plugs. I've been using NGK BR8ES without problems. Those darn Iridium plugs run anywhere from 8 to 10 bucks! The standard plug will set you back a buck 98. Try doing several plug tests with the expensive ones and you'll be broke in no time. What you can do is use the low cost plugs for jetting tests, then go back to to the Iridium when you have it set. :D

You shouldn't need a hotter plug. I'll bet if you get the jetting figured out the '8 will work just fine.

Oh, another thing. What is the mix ratio you are using. I know the manual recommends 32:1, but I found that to be way too rich. If your bike is fully broke-in, 40:1 will run better. Everyone I know runs that ratio.

 

Last edited: Jun 14, 2002

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Nevada Sixx

Member

Jan 14, 2000

1,033

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• Jun 16, 2002

• #5

could adding 2 teeth to your rear sprocket help jetting? since you'll run at a higher rpm and still stay at low speeds?

 

Jasle

Sponsoring Member

Nov 27, 2001

1,358

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• Jun 16, 2002

• #6

do a search on plugs and you will find a post from an engineer at NGK. The newer expensive plugs have tips designed for the harmonic frequencies of the newer bikes. They were having failures where the electrode would break off and cause catastrophic failures. Others in the same thread said just use the cheapies and then change them more ofter. seems like a pay me now or pay me later type of deal.
Jason

 

D

darnjr

Member

Jul 5, 2001

199

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• Jun 17, 2002

• #7

I race Cross Country and I went down one on the pilot and main, and dropped the needle one clip position. This got the spooge to stop on my bike. I mix 40:1 and use the Iridium plugs because thats what it came with. I check the plug after every race and replace it after every four races. The Iridium plugs are worth it to me. Then again, I change my oil before every race. 5 bucks for an oil change is cheap insurance.

 

B

bscottr

LIFETIME SPONSOR

Sep 20, 2001

1,255

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• Jun 18, 2002

• #8

scotth,
Where in NC are you? We have a ride (woods & track) planned for 6/29 & 6/30 at TNT, just south of Charlotte. See the places to ride forum and come on out.

Back to jetting. I have an '01 (came stock with 160 main and 52 pilot). My current setup is the 160 main (above 90 I'll go to 158), 50 pilot and NAFF needle in the 3rd clip position. It's still just a little fat down low. Fuel is 93 octane HP2 @ 40:1. Like CylinderStay said, the bikes came very rich from the factory.

Good Luck,
Scott

 

S

scotth

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Sep 17, 2001

46

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• Jun 18, 2002

• Thread starter
• #9

Tried to get the jetting fixed up this weekend and all I got was more black plugs. :( I got hung up trying to cleanup the bike at low RPMs.
The bike ran rich at idle, the airscrew was ineffective at cleaning it up all the way out. The bike also surged up and down at about 1/8 throttle. The transition from the pilot to the needle seems lean. Above 1/8 throttle, the bike takes off.

Current symptoms

Idle –Rich
Between Idle and 1/8 – Not smooth, garbled.
1/8 – surging (lean I think :think: )
> 1/8 bike takes off smooth power up to WOT

Current Settings

55-Pilot
162-Main
N3WE #3.
Fuel is 93 octane SuperM @ 40:1
NGK BR8ES

My next attempt will be to try a smaller 52-pilot in hopes that the airscrew will then have some effect.
Next, I will lower the needle clip to #4 position to try and fix the surge at 1/8 throttle.
After that, I will try switching back to the stock needle and playing with that in different positions.

Thanks
Scott

******
bscottr,
I am in Raleigh; I hope to get down to TNT someday. I have checked out their web site and it looks real good. How is the trail system, it looks well maintained.

 

Last edited: Jun 18, 2002

S

scotth

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Sep 17, 2001

46

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• Jun 18, 2002

• Thread starter
• #10

I never stated my actual starting point; it was based on the ‘Team Green’ recommended jetting specifications.

92 Octane pump fuel mixed at 40:1
Elevation from sea level to 3000’
Main 165# (Same as stock)
Needle N3WE #3 (Stock is NAFF #2)
Pilot 55 (Team green suggests a 58 but I was rich already, 55# is Stock)

Thanks
Scott

 

B

bscottr

LIFETIME SPONSOR

Sep 20, 2001

1,255

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• Jun 18, 2002

• #11

Originally posted by scotth
I hope to get down to TNT someday. I have checked out their web site and it looks real good. How is the trail system, it looks well maintained.

Click to expand...

I hear the trails are good. Next weekend will be my first time there. Watch for the ride report. :)

 

S

scotth

~SPONSOR~

Sep 17, 2001

46

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• Jun 25, 2002

• Thread starter
• #12

I think I found the perfect setup for my riding conditions :) . The big change was switching to a N3EJ needle. This needle is stock on the current YZ250. A friend uses it in his KTM 250EXC and told me to give it a try. It seems a lot of KTM owners are using it. Do a search for ‘N3EJ’ in the jetting forum at http://www.holeshotktm.com or the KTM forum on this site. After I installed it, I could not believe the difference it made. The needle gave the bike a real smooth linear power band. My jetting is about the best I have ever had it. The plug was light brown and dry, after the same kind of riding that would have left it black in the past. If any KX250 riders are looking for a smoother power band for trail riding, giving this needle a try.

Current setup.

02 KX250
Main 165
Needle N3EJ #3 (Stock 02 YZ250 Needle)
Pilot 55
Air screw 2 turns.
11oz Flywheel weight
FMF Q silencer
Mobil 1 MX2T @40:1
Fuel 93 octane