Jetting questions (kinda long)

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#1
Calling all Carb. guru's
I have 97' KDX200 that up until last spring was completely stock (Until I found DRN & JustKDX) now it has all the bolt on mods, but I have never been able to get the jetting where I feel it should be. I have 3 very frustrating symptoms that I can't seem to get rid of.

1. The bike loads up bad even after idling for only short time (have to hold the throttle wide open in nuetral and just wait till it clears out, smokes like crazy during this procedure)

2. Spooge (BAD)

3. And something I can only describe as a lean bog at partial throttle when the engine is coming down from high revs. I can describe the sound as this: Imagine the engine revved all the way up, now hold the kill button and blip the throttle as the revs come down. Only I don't have to hold the kill button.

The loading up seems to be pointing to rich pilot, The Spooge, rich in general, but #3 seems to be lean pilot? If I lean the pilot any more the bog gets worse and the spooge and loading up stay the same.

My current carb settings are 45P, Stock needle mid clip, 158 main, idle screw all the way in (still doesn't idle well) Air screw 2-2.5 turns

Mods are: FMF Rev, turbine core II, Boysen Reeds, Air box lid off, The top end is about 10 hours old (wiseco)

I run about sea level 60-80 Degree's, I now have the time and the place to get this right once and for all, any help/hints is greatly appreciated. Thanks :)

Oh ya one last thing the gas milage seems to have really gotten bad compared to when new, I compare this to my buddies CR250, he use to fill up twice to my once and now we are about the same, and my tank is bigger.
 
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Mac

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#2
My 200 is setup the same as yours and I ride sea level 60-80 Deg, have you checked your float height? Sounds like it may be too high.

Your bike should idle, it took me a while to get the jetting right after I installed the REV pipe but i'm very pleased with the results now, i'm running a 155 main, 48 pilot, a/s @ 1.5 turns, needle clip in #2. With the rev pipe stay lean on the needle and fat on the pilot, .....well works for me anyway. Like I said this setup screams on my bike but I do get a little loadup when idleing but its gone as soon as I crack the throttle. I may try a 45 pilot when the temps reach 80.

Also, I run golden spectro @ 40:1 and use a BR8ES plug. What are you running?
 
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Canadian Dave

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#3
Given the temperatures and altitude you're riding in your jetting looks too rich on the most part. I'd suggest picking up a 42 pilot jet, a 155 main jet, a 152 main jet and a couple BR7ES plugs. To get the ball rolling try the 45 pilot jet with the air screw set at about 1 turn out, the 155 main jet and move the jet needles clip to the #2 position (second from the top) with a hotter plug. Be sure to do some plug readings at WOT to insure you aren't running lean. See the JustKDX carb tuning guide for more details. Once the air temps get to the upper range you have listed you'll likely need to install the 152 main jet. Again a couple plug readings at WOT will tell the story.

Try both the 42 and 45 pilot jets and fine tune the circuit with your air screw until you get the best possible throttle response. Many people find that the 45 works better with the rev pipe and use fairly small air screw settings, often between .75 to 1 turns out. Small adjustments make a big difference so don't be afraid to play with the air screw.

David
 
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#4
Redline @ 32:1 & 92 Octane pump gas, BR8ES. I'll check the float level. I have noticed some overflow when the bike is on it's stand with the gas on, I was unaware that this could/would have an effect on the bike when running, I've always just closed the petcock when the bike is sitting. I have a 155 Main that I was planning on trying this week. I also have the recomended needle from the KDX site (can't recall the number right now) should I try it, I've heard the stock one is better. Thanks
 

Mac

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#5
You should not see gas coming out the overflow with the bike on its sidestand, float is too high. This will not completely fix your problem but it makes a carb harder to jet. Fix this before jetting!

Most KDXers are running between 40:1 and 50:1 with good results.

I run the stock needle.

-------------Quote from Dave-----------------------------------------------
Try both the 42 and 45 pilot jets and fine tune the circuit with your air screw until you get the best possible throttle response. Many people find that the 45 works better with the rev pipe and use fairly small air screw settings, often between .75 to 1 turns out. Small adjustments make a big difference so don't be afraid to play with the air screw.
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I agree that the pilot circuit is tricky to get right, I found that slightly richer on the pilot is better than slightly lean, I will also be trying a 45 pilot as soon as it shows up(destroyed my old one...long story) and have a feeling I will need to run it around 3/4 turns out. I tried a 42 pilot with temps around 55 deg and performance was awful even @ 1/2 turn out.

I am seriously considering the rb-designs carb mod, this with the REV pipe should be a great combo.
 
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#6
Rejet report

Well I dropped the needle from the middle position #3 to #2, reset the float it was way outta wack, and fiddled w/ the airscrew and ended up about 3/4 turn. This is much better, the bike is still hesitant to rev out in first gear but once it is second or higher it is good. Still have a 158 Main going to try 155 or 152 in a couple days. The weather was about 75 today. Thanks again :cool: