KDX220 won't idle when warm

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lemmy
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KDX220 won't idle when warm

Post by lemmy »

I have a 2003 KDX220 with the 35mm KDX200 carb. I have a new spark plug (BR8ES), new 93 octane gas (44:1 Motul 8002T), CEK needle with clip in #3, 35mm pilot, 1.75 turn air screw, 155 main, woods pipe, newly packed powercore2 silencer, RAD valve (reeds in great shape), float is at 17.5mm and a clean air filter. I can start the bike easily when cold and immediately turn off the choke (might even start without it) and it idles fine. Even after riding for 5-10 minutes it idles fine. But after 30 minutes or so it won't idle or will idle just barely even with the idle screw all the way in and no matter what I do with the air screw. If I pull the choke out it is even worse (so I assume it isn't too rich). I have checked and the idle screw is lifting throttle valve as it is supposed to. I have also taken out the choke plunger and it looks ok, but I don't know what a bad one would look like. Any ideas to try?

I recently fixed the kips (it was stuck open due to previous owner putting the "claw" on incorrectly) and now it opens when it should and closes (slowly). It doesn't seem to return to the fully closed position at idle but it is within 1 tooth on the gear under the slotted cover. I manually turn it all all the way closed and it doesn't make a difference.
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fuzzy
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Post by fuzzy »

Yeah PV won't make a difference idling, but should be fixed.

RAD Valve kinda sucks, but should still run fine.

First thing I start thinking with this symptom is low compression.........
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lemmy
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Post by lemmy »

The bike came with the stock reed cage, I am thinking of going back to that with the Boyesen fiber reeds.

When you say the PV should be fixed, are you talking about it not fully returning to the closed position? I don't really know what is keeping it from returning. I took out the mechanism that is under the right side engine cover and everything in there looked good and super clean. There is no binding, it just seems like the spring in the mechanism that activates it just isn't strong enough to force it back closed.

I don't have a compression gauge, but I will get one tonight and try that.
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Post by canyncarvr »

I'm curious about your jetting.

Why a CEK, for one thing?

Consider:

Image

The two profiles differ only in L-1..the 'K' and 'L' of a CEK/CEL..the CEK being considerably richer at the bottom of the throttle range.

A poor idle can come from a lot of things, jetting is one of 'em. If your main is too far off, the idle will be affected. Same with the needle. Just because the most effect of the main jet and the needle are further up the throttle range, they can make a difference in the bike's idle.

Riders that have compared the two needles in a non-modified carb (#5 slide) have chosen a CEL over a CEK.

Also, your pilot and main are likely at the margins of 'normal' (whatever THAT means)...the opposite margins. A #35 pilot (not mm, btw) pilot may well be fine..but it's on the lean end of what generally works. A #155 may well be fine, too...but it's on the rich side of what generally works. Moreso with a woods profile pipe. A woods (torque) profile will generally take 'less' jet than will a desert (rev) profile.


This goes back quite a ways, but I do recall that my bike didn't idle too well with the Boyesen RadValve. It's also true that about than time I was messing with some pretty silly needles...'A' slopes.


Re KIPS: You mentioned taking the 'mechanism' out under the RH cover. You are referring to the governor rod? The one with the pin attached off-axis on one end? 'Looks good' would mean the pin was perfectly parallel to the shaft..no angle to it at all. Was that the situation?


Oh...does adjustment of the air screw actually effect the RPM of the engine? Does it effect the performance? In what way?


Keep after it. You'll get it!


Somewhat a btw, but do you understand L-1, how it is determined, and how (for example) in this case it makes a difference so low in the throttle range? If not, please do ask. Understanding that measurement is critical to understanding the jetting process. It was for me, anyway.

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Post by lemmy »

(35mm pilot.. :grin: that would be nearly 1.5 inches...definitely make it rich!)

Ok, that makes sense. I have a CEL needle and I will try that tonight. I think the L-1 is the diameter of the needle before the taper right? So a K is has a smaller diamter and is therefore richer...is that right?

When cold or just running 5-10 minutes, adjusting the air screw does make a big difference. If I screw it in it will die, and if i am screwing it out, the rpms stop increasing after about 2-3 turns. After it warms up and it won't idle, it makes almost no difference.

The pin on end of the governor rod looked perfect. It was not bent at all. Also, the mechanism that pin rod sits in (the centrifugal part with a spring in it) also looked fine.

I will also try a 152 main after I try the CEL needle. Thanks for your help.
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Post by jaydollar »

read my idle outa wack post.i to was turning up my idle screw every time i stopped on a recent trail ride and it ran fine.later that day after the car wash i cranked it up to a 10000 rmp idle.(sounded like it)carvr sugjested clogged/dirty main or pilot jet. i removed both and blew air thru where they came from and also ran a .008 strand of wire thru the cross holes and all the way thru the center of the pilot jet.main jet,same thing.re installed and been purring like a tiger every since.i also checked the reed cage boot bolts and both carb hose clsmps for tightnes.J$
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lemmy
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Post by lemmy »

The pilot jet and main jets are clean (checked them last night). But what are the "cross holes"? I sprayed carb cleaner through any of those other holes in the carb body, but I am not sure if they are clean because no light can be seen through them, even if perfectly clean.
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Post by fuzzy »

To help eliminate carb cleanliness:

Get 1 gal Berrymans from auto store

Take out float/needle/etc (rubber)

Soak carb 24-48hrs

Blow out
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Post by canyncarvr »

>|<>QBB<
lemmy wrote:(35mm pilot.. :grin: that would be nearly 1.5 inches...definitely make it rich!)

Ok, that makes sense. I have a CEL needle and I will try that tonight. I think the L-1 is the diameter of the needle before the taper right? So a K is has a smaller diamter and is therefore richer...is that right?
No.

L-1 is the measurement to a specific diameter on the needle. It is NOT, NOT the length of the straight section, NOT the length to where the taper starts.

That specific diameter is often called the 'magic number'. It is 2.515mm.

..and that is the critical part.

**edit** Wrong letter for L-1. Noted below. The point of taper start still applies. Where the taper starts differs as diameter and slope changes even as L-1 remains the same. Okey Dokey?**
CEK: L-1 (the 'K') is 42.20mm.
CEL: L-1 (the 'L') is 43.55mm.

With a given taper (in this case 'C', 1'34", or 1 1/2º taper) a longer L-1 needle will have a taper that starts later (farther down) on the needle than a shorter L-1. The diameter the slope has to reach is 2.515mm, so the longer the L-1 spec, the later the slope starts.

The later the slope starts, the LONGER the straight section (the diameter spec) is in the needle jet, reducing fuel flow when compared to a similar (but for L-1) needle that has the slope starting sooner (SHORTER straight section).


Quiz

Try another change to see what you get.

Consider a CEK vs: a DEK. Both have the same L-1 (42.20mm), but the 'D' needle has a steeper (1'45") slope.

How does that effect the straight section of the needle (keep in mind the straight diameters..the 'E'... are the same, 2.645mm)? Which needle is leaner than the other..and where in the throttle range..and which needle is RICHER than the other...and where?


fuzzy wrote:To help eliminate carb cleanliness:
:hmm: I've not ever HAD a problem eliminating carb cleanliness. It just kind'a happens! :shock:
Last edited by canyncarvr on 02:56 pm Oct 29 2008, edited 1 time in total.

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Post by lemmy »

I thought needles were described as -> taper L1 diamter. So a CEK would be taper C (1'34") , L1 of E (38.15) and straight diameter of K (2.695mm).

http://www.sudco.com/vol33/135-136.pdf
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Post by lemmy »


Consider a CEK vs: a DEK. Both have the same L-1 (42.20mm), but the 'D' needle has a steeper (1'45") slope.

How does that effect the straight section of the needle (keep in mind the straight diameters..the 'E'... are the same, 2.645mm)? Which needle is leaner than the other..and where in the throttle range..and which needle is RICHER than the other...and where?
But with two needles with same L1 and straight section diameter (d1), I would think the needle with more taper (D taper) would have a longer straight section. in other words the taper would begin later on down the needle because it has more taper, it would get to the 2.515 magic number sooner after its taper starts. Since the D would stay straight longer, it would be leaner at this point (1/4-1/2 throttle), after they both hit the 2.515, the D would be richer because it is tapering faster (i.e. getting smaller faster).
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Post by fuzzy »

LOL, Duuuuuuuuuuuuuuuuuuuuuuuuuuuuh
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Post by lemmy »

>|<>QBB<
fuzzy wrote:To help eliminate carb cleanliness:

Get 1 gal Berrymans from auto store

Take out float/needle/etc (rubber)

Soak carb 24-48hrs

Blow out
How about the seat where the float valve seats? That is not removable. Is there any rubber or anything that soaking the carb will damage?

I plan on taking out flat valve, choke plunger, plastic idle screw, float bowl o-ring, drain bolt o-ring, float....anything else I am missing?
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Post by canyncarvr »

heh heh.....you are correct.

The L-1 spec is the length to a point on the needle where the diameter is 2.515mm.

Given only different diameters (the K=2.695, the L=2.705) a 'thicker' needle (CEL) will have a shorter straight section than a 'thinner' needle. The taper has to start sooner on the thicker needle to have the same L-1.

The straight sections are not the same length even if the L-1 spec is the same.

The needle profile chart shows that better than the a/f ratio chart:

Image

Note the inputs are two more widely varying needle diameters so you can see the difference more easily.

The point is the understanding of the 2.515mm magic number and how it effects where the taper starts.

It's probably more important on angle changes. A steeper angle will have a later starting taper than an otherwise same needle. Because it changes quicker, it can start later and still get to a same L-1 as a lesser taper. That will make it leaner lower (throttle range) and richer higher than a similar needle with a 'smaller' taper.

How about this? L-1 is not the distance from the top of the #1 clip to where the taper starts.

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Post by canyncarvr »

Clean the seat of the float valve using a cotton swab with a strip of wet-n-dry wrapped (looped, placed, whatever) around an end. Remove enough cotton so it fits into the float seat, use a strip of sandpaper long enough that you can hold the ends to keep it in place.

Use it wet..use alcohol..kerosene..something like that. WD40 would work.

Don't go overboard with it. Using 280 grit paper and spinning it around in the float seat for 5-10 minutes is overboard. Look at the seat. Use the swab/paper strip to remove varnish, crud, oxidation. It's a 'gentle' process.

Remove the jet block. When you take the main jet out of the needle jet, it will (should) come out the top of the carb.

The cap has a gasket in it. I don't suppose you would put the cap in the Berryman's....

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Post by lemmy »

When you say remove the jet block, are you talking about what is outlined in black in this picture (sorry for the poor quality phone pic)

Image

I took the main jet out, but it won't come out. It looks like I have to remove the torx screws on the bottom side, one of which is shown in this picture:

Image

I have never removed those becuase of the "do not remove any parts not shown in this exploded diagram" disclaimer on the sudco website. Is it safe to remove them to get the jet block out? Do you see anything I have left in that might be damaged by soaking in the Berrymans?
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Post by jaydollar »

the little holes, about four or six of them that go sideways across the pilot jet.
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Post by fuzzy »

You're ready to dip.

RE Needle/seat....Seat is fine....Only rubber is on the needle itself. These are solid steel (lapped) on a carb setup for alky, BTW.
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Post by lemmy »

Ok, I am gonna dip tonight. The store I went to last night only had Gunk brand and I read that wasn't as good. I think autozone carries the Berrymans.
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Post by fuzzy »

Yep....Pretty sure that's where i picked my last can up...
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