Fast Freddy Quick Needle Question

[Fast freddy]

Hi guys . I'm at 5600 above sea level in Montana and right now I'm running a 54 pilot , 162ain clip on the very bottom position. At least 2 1/2 turns out on air screw. It's an 01' 220. I too think 1/8 to 1/2 throttle could be sharpened up a little. Last night I when riding everytime I would pin it in 6th gear and it would stumble at the very very top. If I held it almost wide open but not quite , t stayed right there where I wanted it. I thought I was getting pretty close w the jetting. Do I go down 1 on the pilot? And up 1 on the main? Or do I shim the needle and see if that takes care of the stumble at w.o.t throttle?

[Slick_Nick]

Your jetting is way out to lunch.

I’m at 4000’ in Alberta and I have a 38 pilot, 150 main, and a DEK on the 2nd clip.

*Edited. Updated clip position.

[SS109]

I agree with Nick. That jetting is waaaay off. I should require larger jets than you, me being at 2000ft, and I'm at 150 main, 38 pilot jet, CEK that is on the 3rd clip, screw normally between 1.25-1.75 turns.

I think you should be on a 145 or 148 main, a 35 or 38 pilot jet, and get a known good CEK or DEK needle. Then start following the jetting guide (located here: viewtopic.php?f=105&t=1156 ) and get it dialed in.

[KDXGarage]

A KDX is not going to run very smoothly at wide open throttle in 6th.

You may want to check a pressure and vacuum testto make sure the jetting is not a Band-aid for a mechanical issue.

I split your post off into its own thread. If you have a unique question, give it a unique thread of its own instead of a asking a similar question in someone else's thread.

[John_S]

If it were mine I would put it back to stock and follow the jetting guide to a T. 45 pilot, 1.5 turns on the air screw, middle clip, and a 145 main if I remember correctly. I think your overly rich pilot and main jets and are throwing it off.

My 220 at sea level (but hot thin air) has a 40 pilot, 1.5 turns out on the air screw, 2nd needle clip from the top, and a 148 (maybe a 145) main. The pilot, needle, and main never really have to be messed with. Just a slight air screw adjustment depending on the humidity.

The quickest test I know of for the air screw adjustment, considering your jetting is close and the bike is fully warmed up and "cleaned out" is to go walking pace in first gear and crack the throttle wide open and back off as fast as you can. If it bogs like its out gas, turn the screw in a 1/4. If it stutters, out a 1/4, and if it wants to pull the wheel up immediately its good. If its really close it may only take a 1/8th turn.

With the ideal setting on my air screw, the bike will lean bog doing that test if its not fully warmed up. Always make sure its at operating temp before adjusting any circuit.

[Fast freddy]

Thanks guys . I agree my jetting is "out to lunch" hehe. I. cant believe it runs anything like it's supposed to with that setup. When I got the bike it had a 22.5 pilot, 135 main, and wouldn't idle at all and bogged when. Given gas . Going to do what you guys said and start over with stock jetting and go from there. I'll let you guys know what I end up with. Thanks again

[Fast freddy]

Hi guys finally had a chance to try and work something out with my jetting. Not sure if I said before, but my jetting was way off. I was at a 54 pilot and a 168 main , and oddly enuff my bike ran pretty damn good,. SE members suggested I go bck to stock so that's what I did. Only mods it has is gmarly pipe and turbine core 2 silencer. I started working my way back from stock and now I'm at a 32 pilot and a 140 main. It runs pretty good now. It has just a small bog right off of idle bit that's it. Clip on the bottom groove. Any suggestions? Thanks alot for ur help guys

[KDXGarage]

32?!

That does not sound right.

[SS109]

32?!

That does not sound right.

Exactly.

OP, what carb are you running? I've seen some crazy jet numbers (22.5 and 32) that don't match up with Keihin PWK carbs used on KDX's. The smallest pilot jet available is a 35.

[Fast freddy]

It's the stock pwk that it came with. It had a 22.5 pilot and a 135 main when I got it tonight I put a 35 in and it starts fine , idles fine, but when I adjust the brass screw I can turn it all the way in and the idle just keeps getting faster. Does that mean it needs a bigger pilot?

[SS109]

Yes, I would say you need a bigger pilot jet. That's weird, though, as I'm at 2000ft and run a 38 pilot and it's spot on. I would think at your elevation it should be at least a step below mine. Oh well, throw in a 38 pj and go from there.

You may want to check a pressure and vacuum testto make sure the jetting is not a Band-aid for a mechanical issue.

I'm thinking this testing might be a very good idea.

[Slick_Nick]

Yes, a 38 pilot should do ya.

When I was getting my KX250F dialed in, I got to explore the wonderful world of four stroke jetting the Keihin FCR. Because of my high altitude, I actually had to go UP two sizes on the pilot, opposite of a two stroke. The reason being, the engine doesn't make as much vacuum up here as it does at sea level, and as such can't suck as much fuel through the pilot jet. Makes sense to me. I did have to go quite a bit leaner on the main and needle of course, it was just the pilot and accelerator pump circuits that needed more juice.

Anyways, story time over. Try a 38 pilot and go from there.

[Fast freddy]

Hey thanks guys . I'm getting ready to try a 38. Now that you brought up the fact the carb can't pull as much vacuum up here because the air is thinner makes complete sense. I think it's going to be a whole different bike when I get the jetting dialed in. I'll report how it goes. And lost a bike pic if I can figure out how. Thanks guys. I really appreciate it.

[Slick_Nick]

Hey thanks guys . I'm getting ready to try a 38. Now that you brought up the fact the carb can't pull as much vacuum up here because the air is thinner makes complete sense. I think it's going to be a whole different bike when I get the jetting dialed in. I'll report how it goes. And lost a bike pic if I can figure out how. Thanks guys. I really appreciate it.

That's applicable to a 4 stroke only. For a two stroke there isn't as much delay in between the intake pulses, so the fuel comes out in a consistent stream. Hence why you need much leaner than stock. On a 4 stroke at idle, the fuel basically stops being sucked out of the jet, and in fact starts to fall back down into the bowl in between intake pulses, hence why a larger pilot jet is needed.

honestly man, try a 38, a 140 main, and 3rd clip on a CEK or DEK. I bet that will have you pretty close if not bang on. Of course, don't just set it and forget it. Fine tune from there. A properly jetted carb is sooooooo satisfying, it's like free horespower and rideability.

[Fast freddy]

Oh...got it...thanks slick Nick. K so I tried the 38, too lean still, out a 40 In, at least I have some adjustment in the screw now I think it's pretty close. Still have a bog right off the bottom, and it feels like my main is a tiny bit small(140). I'm on the bottom position with the clip. I think if I go up one size on the main now it'll be pretty close...what do you think?? Ikeep forgetting to see what needle I have ...

[SS109]

If your highest idle comes in between 1 to 2 turns out it's good to go. Remember that once you find your highest idle to always go back in 1/16th to an 1/8th on the idle mixture screw. Throttle response should be better.

Now, put your needle in the middle clip so you can sort your main. I'd bet money you'll end up with a 145 or 142 main.

[Fast freddy]

Ok cool. I bet ur right. Highest idle with the 40 pilot is about 2 turns out. The main doesn't seem too far off I'll start with a 142 in the middle position. I still had a bog on the bottom when i cracked the throttle
with the 40 and 140 main. What do ya think that's all about??

[SS109]

Have you checked your float height? Sometimes your bike can run overly rich due to the height being too high. I set mine 18mm and NOT 16mm like factory. Also might be worth checking to make sure your jet block gasket is good.

[Fast freddy]

Ok .. so I didn't have a 142 main so I went straight to the 145. I left the needle on the bottom position and it's pretty damn close! Finally. It's nice and crisp and pulls hard through the whole range. The only thing it does that I don't like is the idle won't seem to stay where I set it. And it doesn't return to idle as quick as I'd like when I let off the gas. I just put in a new jet block gasket. I just visually checked the float height. I didn't actually measure it. I checked my throttle cable to see if it was too tight and messing with the idle and it is not. Thanks for sticking it out with me slick Nick muchos gracias! It's pretty darn close now. I changed idle screws and it was worse with that one.. .

[Fast freddy]

So I'm at 5000-8000' elevation. Gmarly pipe , turbine core 2,. Snorkel removed . Holes in airbox lid. And I'm running a 40;pilot 145 main, still not sure what needle, but this is the best it's run since I got it. I'll try and post a pic. I e done alot to it since I've had it. Not a bad score for 1 days labor puttin a furnace in for a guy... My ktm was just about ready to **** the bed so it was time for a new one and I couldn't be happier. I already love this bike and it hasn't even ran good till now. Thank again! Peace out fellas... Very good advice slick Nick!