Can't get an idle... Looking for ideas

[axel-moto]

Hello friends,

I have been working on Jetting a new to me 2001 KDX200 and I am having trouble getting the bike to idle. I'll post below more info on jetting and what I have tried so far - looking for ideas or stuff I may have missed.

The Bike:
2001 KDX 200
Stock bore, Steel Sleeve
Airbox Snorkel Removed, new air filter
Stock Reeds, in good shape (no light/ curling/ carbon)
Gnarly Exhaust

The Carb: original beat to hell PWK 35 (as in, looks pretty scratched up inside and out).

Current Jetting (for sea level):

Pilot 45, Main 165, Red JD needle 3rd clip, 5th slide, Air Screw 1 3/4 out.
Float set at 16mm by using the "blow in the tube and set where it seats" method.

Bike will fire up with the the throttle cracked and keep running as long as the throttle is cracked. It will run through the gears and pull decently through the rev range. Feels a bit rich and down on power, but runs. However, it will not idle.

What I have tried so far:
The bike came with the following jetting the PO claimed worked at 3000ft. It bogged pretty bad under throttle until the last 80% and didn't feel right at all, but it idled:
Pilot 45, Main 150, Stock Needle 3rd clip.

- I took the carb apart, cleaned it with compressed air and carb cleaner
- Replaced the Jet Block o-ring
- Tried original JD suggestion of 42/165 4th clip and didn't idle either.
- Checked carb boots and no cracks or damage. Ring clamps working well and tight.
- Blocked off part of the airbox to make sure it wasn't leaning out, didn't make a difference. Tried with no air filter to check for too rich, also didn't make a difference.
- Mixture screw in either direction doesn't help.
- Idle screw doesn't seem to do much to the idle but I checked that it indeed is raising the slide.
- Jets are all Keihin branded, both 42 45 and 165 are new.
- I set the float height twice, once using the version in the manual (carb horizontal and measuring from base) and then another time by blowing in the gas tube and setting the height at where it was sealing.

Additional random info:
- Plug looks wet from gas but not carbon fouled.
- The PO had a inline fuel filter but was using very slim tubing, I replace with a direct line of correct diameter.
- Checked compression, solid 150 every time
- Changed throttle cable (I don't think this has to do with anything on this bike but you never know).
- The carb overall looks pretty beat up and I'm seriously considering getting a lectron, especially given that I will be riding this at wildly different altitudes (one of my spots is sea level, another is 6k)

What I will try next time I am near the bike (it's at a storage place, I can't work on it during the week while at work):
- Remove plug and kick it in case there's a load of gas in the cylinder throwing things off, put a fresh plug in.
- Lean the main a lot just in case, because it seems from the jetting info 165 is on the richer side. So probably going to 155 or 150 and back up.
- Go back to the po's jetting that ran bad but idled and work up from there. I really hope I can run the JD needles though, I have them in my DRZ and they are very good in that bike.

Any input on what I may be missing is super appreciated. I haven't worked on PWK's before so appreciate any input.

[kdxdazz]

A common issue with the old carb due to a worn/corroded emulsion tube,
First get rid of that JD needle, its a terrible needle for the kdx, it allows huge amounts of fuel in at idle due to the taper and straight diameter
Try source an 1174 needle or the 1173, reinstall the airbox snorkel, drop down to a 42 pilot jet, this will improve things dramatically
I also had the same issue when I first bought the kdx, no way it would idle which made it miserable to ride in the jungle, followed all the jetting advice including RB in the US, not even close

[axel-moto]

A common issue with the old carb due to a worn/corroded emulsion tube

Well, I did not know this could be an issue appreciate your input!

First get rid of that JD needle, its a terrible needle for the kdx, it allows huge amounts of fuel in at idle due to the taper and straight diameter
Try source an 1174 needle or the 1173, reinstall the airbox snorkel, drop down to a 42 pilot jet, this will improve things dramatically

The needle the po had in there was a 1174, it was my understanding the jd red was slightly leaner on the straight section of the needle but I'll put the 1174 and 42 back in and test from there.

[kdxdazz]

The red needle is leaner than the blue needle but not as lean as the 1174, 2.74mm Vs 2.725mm for the red needle but the tip of needle also adds to idle as this extends in to the main jet, the red needle has a much thinner tip than the 1174

[billie_morini]

axel,
kdxdazz knows his way around needles & emulsion tunes.

Good on you for replacing the jet block o-ring. My 1999 kdx 220 purchase used about 5 years ago also needed the flat, circular gasket in the carb top. This gasket was absent and it took me a while to discover this. Idle improved a lot when new gasket was installed

[axel-moto]

My 1999 kdx 220 purchase used about 5 years ago also needed the flat, circular gasket in the carb top. This gasket was absent and it took me a while to discover this. Idle improved a lot when new gasket was installed

Good call out! I did replace this - I bought a genuine keihin rebuild kit and this was included... it took me a sec to figure out where it should go!

The red needle is leaner than the blue needle but not as lean as the 1174, 2.74mm Vs 2.725mm for the red needle but the tip of needle also adds to idle as this extends in to the main jet, the red needle has a much thinner tip than the 1174

Good info thank you - I will put the 1174 back when I am working on the bike this weekend after turkey day. Happy thanksgiving yall!

[axel-moto]

Commenting here with an update - problem solved. Here's what worked:

I put the 1174 needle back in (3rd clip) and went with a 42 pilot and 160 main. This worked, I got an idle! But the idle is was still kind of inconsistent.

I then committed a sin... I know this is not ideal but I felt like kdxdazz was right on the money calling out the emulsion tube being damaged due to the age of the carb. SO - I bought a Chinese replica of the PWK 35. The genuine Keihins are pretty pricey and this was a way to test the theory for cheap.

I swapped all the jets for genuine Keihin Jets and used my genuine Keihin 5 slide. Idle with the 1174 was super crisp and it pulls nicely through the revs and builds power well. Starts from cold on choke and can be ran shortly after.

I got a chance to actually ride the bike today and it felt really good. Feels good on idle and off idle. Builds up to power well, although the midrange felt like it could be improved. Still some fine tuning to do as where I ride is a bit different conditions than where I tuned the bike.

Final Jetting:
Replica PWK Carb
1174 needle 2nd clip
Mixture Screw 1 1/2 turns out
42 Pilot
160 Main

I'm still debating next steps here as I fine tune the jetting. Either get a new Genuine PWK, or get a stic bloc to replace the emulsion tube and gain better tolerance to elevation changes. Or go with a lectron/ smart carb although I've heard mixed reviews of these.

[kdxdazz]

Glad you got it sorted,the emulsion tubes in the Chinese carbs are usually incorrectly sized, being on the small size, if you have an 1173 needle I would try that as it's smaller than the 1174 on the straight diameter
You could also try raising the needle clip 1 position on the 1174 needle but these are only work around solutions for incorrectly sized emulsion tube or straight diameter
Also test with E10 fuel as it runs a lot leaner and this will give you some indication of where you are rich or lean
I would also test a 165 main jet to confirm the emulsion tube is on the small side

[axel-moto]

Thanks kdxdazz!

I'll try your suggestions experimenting with the needle height and main size. For my knowledge, how does changing main size show issues with the diameter of the emulsion tube?
I don't have a 1173 but might do a jetsrus order soon. Do you have any input on the Del/Dek needles I see talked about a lot on this forum?

[kdxdazz]

The main jet effects all the way down to 1/4 throttle, with a CV carb it effects all the way down to idle
Del is even richer than the JD needles , I couldn't even get an idle with it, i understand people use these super rich needles when they put in a rev pipe and remove the airbox lid but a highly doubt this gives optimum low end jetting

[billie_morini]

axel-moto said, "Commenting here with an update - problem solved. Here's what worked:

I put the 1174 needle back in (3rd clip) and went with a 42 pilot and 160 main. This worked, I got an idle!"

This is a really good update. So is the clever testing you are doing the mix-mathcing. That's clever!

[axel-moto]

Thanks billie!

Another quick update, adjusted the needle and bike runs top with needle on 3rd clip.
I'm gonna play around with a leaner main next but it feels really good. I have a 40 pilot in the mail as well just because.
Can you tell I'm hooked on getting this thing dialed?

The idea is to get my jetting set up perfect for my main riding areas (Carnegie and Hollister) which are both 500-3000ft. It's also cold these days (40*) and humid so likely gonna adjust this for the season.

Got to ride a cool GPX 300L today... a lot of bottom end power but I still like the way the KDX delivers the power it has.

[billie_morini]

Very good news, axel-moto! It's fun to hear how things are progressing. Your intensity is also appreciated. I'm the same way for both fuel-air mixture and suspension.
Also, fun to know where you ride in California. I know these parks a little bit.

[Chuck78]

Another quick update, I adjusted the needle, and bike runs top with needle on 3rd clip.
I'm gonna play around with a leaner main next but it feels really good. I have a 40 pilot in the mail as well just because.

Can you tell I'm hooked on getting this thing dialed?

Great to hear!

It's always an incredible feeling to properly tune a bike that has been running "just okay" or has had some stumbling issues but is fairly rideable, just not mind blowing... and then get it jetted properly and experience the ecstatic satisfaction of just how drastically better it performs when it's jetting is set up in the most ideal configuration!


Even going from a bike that runs "acceptably enough" to an owner who is an aspiring amateur mechanic, it's an amazing feeling to jet the bike properly and see just how significant of performance gains can be had going from "okay" running to "WOW" permagrin type performance...



It was also an interesting experiment when my buddy told me after a hard crash, the bike performance started dropping off and was no longer amazing as it was when we got the jetting really dialed in earlier that year to the point where our minds were blown at the power delivery increases on his '99 KDX200H...
Well, eventually... I got out of him that he had both switched premix oils, and switched from 32:1 originally up to 40:1 or 50:1, and had topped off a half tank of 32:1 at the beginning of the ride where he had the hard crash, with his new oil and new mix ratio.... That also told me that since he went richer on the mixture (thinner oil ratio / more gasoline, hence richer air fuel ratio, do not ever refer to 50:1 as "leaner" than 32:1 thinking lean vs rich references the oil dilution, lean vs rich ONLY references air fuel ratio! very common amateur nomenclature mistake which drives me crazy...) - he effectively richened up his mixture by a jet size or two on the main, a jet size on the pilot, and 1 needle clip position lower (raising the needle 1 position). Less oil = more fuel flowing through the same jets = richer air/fuel ratio than what the same jetting was previously delivering...


Always jet with the oil ratio and type of oil you intend to consistently use, as different oils at the same ratio will even make a slight difference in jetting and even in necessary ignition timing! Jaguar has experimented with this quite a lot, and has some writeups on his website about this...


Anyways, I'm really happy to hear you've got the running issues solved through jetting trial and error and successes! Congrats, and welcome to the forum!