CaptainObvious

Formally known as RV6Junkie
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KDXFreestyle said:
I now understand it, excepot for the signs of which way to go.

Then you don't understand it.

A bog is usually a sign of a lean condition. If the bog is happening below 1/4 throttle it is your pilot circuit. 1/4 to 5/8 throttle it's the needle, above that the main.

If the bog is happening in the pilot circuit it may be tuned out by the pilot screw. If the screw is turned in more than 1/2 a turn consider a larger jet. You say you are running a 45 now. In this Weather that sounds very rich.
 

70 marlin

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KDXFreestyle said:
thanks for the advice, asnd u are right.. SUPER easy... My friend showed me how to do it, but the only thing is, what signs do you look for to know which way to go? My hjetting is stock, except for a 155 Main. Th ebike runs AWESOME, and idles fine, but it has a bog, and wont pull a gear if your near 1 too high or so. other than that the bike is SO AWESOME! What do you think about this issure with the bog? What sign is it? Would a 45 pilot help?
Thanks for all the info, it helped a lot. I now understand it, excepot for the signs of which way to go.
The mods I have on now are the PC pipe, and the boyesen pro series reeds.
Thanks again! :thumb:
First read this http://justkdx.dirtrider.net/ go to carb tunning tech section and under stand it! time to study.
nexted put your pipe on and do a plug chop! figure out where your bike is. a crisply jetted KDX will fly with very little bog if any.
 

Rhodester

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May 17, 2003
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Freestyle,
When you accelerate hard and have a bog (hesitation?) put your choke on and see what happens. If it improves, you're too lean. If no change or worse, you're too rich. If too lean I would start with 1 or 2 main sizes richer and maybe raising the needle 1 clip position (lowering the clip). Do your changes one at a time and be sure to write down the reactions the bike gives you with each change. Remember, temperature plays a big part in all of this. You'll have to lean at least the main jet as summer temps approach.
 

KDXFreestyle

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Nov 19, 2002
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ok thanks. right now I am going to go look at my pl.ug and see what it looks like. My bike bogs a LOT when its in say 1, or mabey half a gear to high, it wont pull. The only jet I changed was the Main. Stock was a 160 I believe, and I put in a 155. Th ebike SCREAMS on top though, and hits pretty damn good, just that bog. If I have a 48 in there now... and i put in a 45, that will make it leaner, correct? (less gas)
The air screw helps with the pilot circuit, am I correct? And in (turning it right, I believe) will make it more rich? Please correct me if Im wrong.

Just so you guys know, I installed Boyesen pro series reeds at the same time as the pipe, but im not sure if that has any effect on jetting.

My plan is to look at my plug, and see what happens, my bike is smoking a lot, but i have really rich gas. Im not positiv on the mixture, but it should be somewhere around 32-40:1... mabey even richer (richer to me means more premix in the gas, right?.. thats what I mean when I say it)
Then try out the 45 pilot and see what happens
Then try the 42 if it doesnt, or helps a little
Then mess with the air screw and needle position last.
does this sound like a good plan of attack?

Thanks again
 

KDXFreestyle

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BTW... my bike will accelerate fine if im on the throttle befor ei shift, and after, but if the revvs go low, then it wont pull back up. i will try the choke idea, that is what i was looking for, it makes sense to me, because the choke adds more gas, and is a good way to tell. Im starting to understand this! ITS A MIRACLE! :clue: :thumb:
 

CaptainObvious

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KDXFreestyle said:
ok thanks. right now I am going to go look at my pl.ug and see what it looks like.

Don't bother looking at a used plug. I can tell you right now it will be black. You want to read a new plug that hasn't had a lot of idle/mid throttle time on it.

KDXFreestyle said:
My bike bogs a LOT when its in say 1, or mabey half a gear to high, it wont pull.

~cut~

Stock was a 160 I believe, and I put in a 155. Th ebike SCREAMS on top though, and hits pretty damn good, just that bog.

What transmission do you have? Half a gear too High :think: If the bike bogs and then pulls strong (at WOT) that is a sign of rich jetting. Once again, to be clear, we are not talking about a bog as you roll on the throttle, but at WOT. A lean main jet starts off strong at WOT and looses its hit. Caution: if it's too lean it will cease the engine.

KDXFreestyle said:
If I have a 48 in there now... and i put in a 45, that will make it leaner, correct? (less gas)
The air screw helps with the pilot circuit, am I correct? And in (turning it right, I believe) will make it more rich? Please correct me if Im wrong.

Yes, 45 is leaner than a 48 due to less fuel. Turning the air screw in (to the right when viewed from the top of the screw) does richen the pilot circuit. Tune this circuit for best throttle response.

KDXFreestyle said:
Just so you guys know, I installed Boyesen pro series reeds at the same time as the pipe, but im not sure if that has any effect on jetting.

Look at your bike as a system, not this thing makes it rich and this thing makes it lean. Jet for what you have, not what you think it should be.

KDXFreestyle said:
My plan is to look at my plug, and see what happens, my bike is smoking a lot, but i have really rich gas. Im not positiv on the mixture, but it should be somewhere around 32-40:1... mabey even richer (richer to me means more premix in the gas, right?.. thats what I mean when I say it)

Choose a pre-mix ratio (32:1 is good) and leave it alone. Your pre-mix ratio has little to due with a smokey exhaust. A rich mixture (gas/air) is what usually causes a smokey tail pipe. With that said, before you go chasing the jetting, make sure you have a clean silencer and air filter.

KDXFreestyle said:
Then try out the 45 pilot and see what happens Then try the 42 if it doesnt, or helps a little. Then mess with the air screw and needle position last. does this sound like a good plan of attack?

Air screw first. You decide on the correct pilot jet based on throttle response from adjusting the airscrew in and out.
 

Brian

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OK, so you say your bike just "doesn't pull very strong once the revs die down" when you're riding a gear too high? Try downshifting. It sounds like your problem is not jetting, but a lack of sheer horsepower/torque. You can't expect a KDX to pull hard when you're in the wrong gear for the application.
 

KDXFreestyle

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my problem is not downshifting, and I mean thalf a gear when im not at WOT. WOT is poerfect.. from about mid on up it pulls like a screaming banshee! just if I let my revvs get a little too low like before half throttle, than crack it liek I usually would it will bog, then I have to let off and roll it back on or fan the clutch. it never did this before.
 

mnnthbx

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Apr 1, 2003
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I'm telling you, I went through the same crap. My money says a 42 pilot cures your problem. (I realize every bike is different) Since your getting familiar with this stuff, try it and see. Jetting is lots of trial and error you know...... let us know how it turns out.
 

KX02

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Jan 19, 2004
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My KX also came jetted pretty rich stock, this is as it should be for safe break in. I installed a Fatty on my bike and I still ended up going to the next size smaller main jet. I would say over all the fmf pipe probably does not require different jets. I bought Boyesen Pro series reeds for my bike, but have not installed them yet. Boyesen does say their jets will probably make the bike run richer and would therefore require you to install a smaller main jet.
 

Rhodester

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May 17, 2003
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If I'm hearing you right it sounds like you're too lean on the main. If you're at sea level in winter time I'd say that you're probably going to be too lean if you go below that stock 160 main by the way its acting. Try sticking that 160 back in and raise your needle one clip for starters ( one clip position lower). I'd be hesitant to go less than a 45 pilot to start with (for current conditions). If your throttle reponse just off idle is good after adjusting the air screw, note how many turns it's out from full in. If it's more than about 2 then it's time for the next leaner pilot. If it's less than 3/4 then it's time for the next richer pilot. A bike running on the lean side will run extremely powerfully (crisp) when you can get it on the pipe (higher RPMs), but, you're playing with fire and can seize it if you're not carefull. Tell tail signs of this are a big hesitation like what you're discribing; a hard time getting it "on the pipe".
 

john_bilbrey

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Mar 22, 2003
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You have a lean bog. I went through the exact same thing on my 220 just a month or so ago. It would run like a champ mid to top, but from around idle and go WOT, it would die. Bump your main up a size (or two or three) and see if that doesn't improve things for you. (I was three sizes too small on the main. I too thought that since it was right off idle that the problem was the pilot. But you have to remember, it's not RPM but throttle position that determines which jet is in play.)
 

KDXFreestyle

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ok, before I try the pilot, Ill try going back to the stock jetting and see what happens.
Thne I will try the 45 pilot with the 160 Main. Then the 155 main with the 45 pilot. Ill let you know what happens when the ground dries up a little bit
 

KDXFreestyle

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HMMMMMmmmmHMMmHMm

This is such a pain in the arse! I tried every combo with these jets... 160, 155 mains, and a 48 and 45 pilots. They all seem to feel the same to me. They all have a bog at approxametly 1/2 throttle with every combo. And also with all the combos, the pull like a screaming banshee on top! :aj:
I also tried playing with the air screw at these positions 1 turn out, 1.5 turns out, and 2 turns out. Still felt the same. Also, with all of these combos of jets, the bike idles fine. now... With fresh gas, and a 42:1 gas mixture, 45 pilot, and a 155 main, the bike still has the bog. When I rode it with the choke on it sorta took away the bog, still pulle don tom, but ran funny. please HELLP!! :eek:

Again I summon the Jet Gods! :worship:
 

jboomer

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Half throttle relates to the clip position on the needle right? Have you tried adjusting the clip up and down.....it's free and only takes about 10 minutes.
 

Rhodester

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May 17, 2003
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Try raising the needle (lowering the clip) as well as richening the main some more. Try a 162 or 165 main jet. After that, if you still are having trouble look at float level, clogged fuel petcock, and then vacuum leaks. My guess is that it is cold there and it just takes a richer than normal main jet in these winter conditions. My 200H takes a richer main than what I see people regularly using on this site, and that's at 2600' elevation and warmer weather. If I were using the stock needle on my bike, I'd have to have it in the bottom clip position (#5) and a 162 main at my elevation and 70 degree weather to get it in the ball park...and I would still be fighting a slight hesitation/flat spot when "wicking it" at low RPMs ( I run it with a -35 pipe and no air box lid). The choke is the big indicator to me that you are still too lean in the needle clip position and the main.
 

KDXFreestyle

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Nov 19, 2002
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lol I DOO!!!.. ok so... damn main jets! if someone could walk me through the process of how to change the clip position I should be all set! I will try raising the needle, and running with a 160 Main. if that doesnt work Ill be Forced to go out and buy another main.

Does th ePilot sound liek its OK?

In the summer in hot humid weather, what jetting will most likely be affected? What will I probably have to change?

Its almost there guys!

Thanks again jetting gods! :worship:
 

CaptainObvious

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KDXFreestyle said:
if someone could walk me through the process of how to change the clip position I should be all set!

1. Unscrew the top of the carb and remove the slide;
2. Pull the spring all the way into the cap and hold it there;
3. Push the cable into the top of the slide, move it to the side, and remove it;
4. with a 6mm driver, remove the top of the slide;
5. push up on needle and remove from slide;
6. remove clip from needle and move one groove up towards the top to lean, one groove down to richen.
7. reassemble
8. Ride
9. realise that dealer isn't crazy...you are :laugh:
 

KDXFreestyle

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Nov 19, 2002
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I know.. this should help me because .. when I think abotu it.. more gas will be flowing, so when I crack it.. it wont bog.. i hope this fixes it!

THANK YOU TO ALL THE JETTING GODS! :worship:
 

Rhodester

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May 17, 2003
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45 pilot should be OK in this weather. As it warms up you'll need to lean it out from what is ideal now. At 70 degrees you'll need to be maybe 2 sizes leaner on the main and maybe 1 leaner on the pilot. At 90 degrees you'll need to be another 1 size leaner on the main and maybe just a little more counterclockwise tweek on the air screw. Summer heat may require dropping the needle 1 clip position. These are just ball park estimates.
 


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