jetting woes,

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Oct 29, 1999
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#1
ive just come in from trying to get my bike jetted, first off its a 97 200 with fmf pipe and silencer, open airbox, boyseen power reeds, premeium gas mixed at 40:1 yamalube, 2r, i pulled the carb that was supposed to be jetted when i bought the bike, "never belive anyone" inside i found 158main, 45 pilot, so i followed advice here and dropped to a 152, 42, setup, it was 65degrees here and i think my elevation is about 2,200ft but in mid clip position it was running way lean, so dropped the clip and tryed again still lean, so pulled the carb back off and changed to 155, 45, in mid clip and airscrew at 1 1/2 turns out, much better but still seems to be a bit lean, how can this be? everything ive read says this should be way rich ,it started to rain before i could try moving the clip down to try to richen things up a bit, not sure what to do at this point, i could always go back to the 158, 45, setup but on cold start it was a bear, easy to foul a plug but once warm ran ok, any positive feedback on my delima would help, im starting to pull my hair out, and i dont have a much to spare, HELP ?
 

Mikeb

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Jun 8, 1999
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#2
Joe, Is the plug gray or white after you do a plug chop? My bet is that it is not. It sounds like a similar problem I also had, the bike would run fine on the top end but had a lean bog (BOOOWAAAHH) when throttle chopped hard at low RPM's. Fredette called it a "Classic Lean" condition. The fix was to turn the air screw in ALOT. I found it ran best at 1/2 to 3/4 throttle out from fully seated. I know this sounds weird but it works for me. It still will burble if throttle is rolled on slowly due to excess fuel but it is hardly noticable. The best set up I have run across is a 155 Main in the winter and 152 in summer, 45 Pilot jet, Air Screw 1/2 turn out, needle in the 2nd clip from top.

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Mikeb
1998 KDX200  
http://www.justkdx.dirtrider.net
 

canyncarvr

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Oct 14, 1999
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#3
What does 'running really lean' mean?

By the 'book' you would start with the main jet using the chop method (WOT with a load..best case being a long uphill you can run in 6th). I would guess that's not what you're doing if as a 'fix' to 'running really lean' you are changing the clip positon. Clip position is good for about 1/8-1/2 throttle. WOT isn't going to affected diddle by changing the clip. ...well, unless things are pretty way off.

You have a printed copy of the needle effects chart? CDave has it on justkdx.

Anyway, start with the main using WOT/chop. Changing other circuits first is a waste of time. An incorrectly set main can falsely indicate every other circuit in the bike.

As mike says...don't be afraid to run the airscrew in. As little 1/16 of a turn can make a big difference. That circuit is adjusted by 'seat of the pants' throttle response. The idea of setting it for 'high idle' is just a place to START!. Use yur fanny to fine tune it.

Your first jetset wouldn't be too far off for a 200 with a rev (KG30) pipe. A torque (KG35) will require a bit leaner setting..meaning require a leaner jetset..than the rev.

Any further questions, please indicate which pipe you have, your needle# and whether or not any porting has been done. Porting will generally require a bit richer setup.

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  • OLD member
    'oh-oh' KDX 200
    '86 Nighthawk 700 SC
    (a motorcyle even if it doesn't have a chain!)
 

Russ

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Jan 17, 2001
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#4
canyncarvr,
Thanks! You actually answered a question that I have been meaning to post. I had the K30 and was actually running the stock jets when it was about 35 degrees and it seemed fine! So I was really confused as to why so many people were recommending such lean jetting. I just put a K35 on the bike and what a difference! The thing runs like a pig on the stock jets now! It really wants leaner jets bad. I really haven't had time to do much with the bike, but just wondered if what I experienced was normal, and apparently, it is. You, me, and a guy with the RB carb mod have reported the same thing.

Russ