HELP!! Low speed rough running on KDX220

Y

yzfjim750

Member

Mar 12, 2004

21

0

• Jul 3, 2005

• #1

Hi all,
My problem is slow running which is not crisp and stutters then clears it throat and flies up the top end of the rev scale.
The jets I am running is a 152 main and a 42 pilot, the needle is standard and position is in the middle on a 90 kdx200 35mm carb, float height is bang on 16mm as recommended.
A full throttle plug chop revealed jetting to be spot on.
I am also using a FMF gnarly desert pipe with a powercore 2 silencer and the airbox lid removed.
could this be a problem with the kips valves??
I have checked the valves with the exhaust front pipe off and they all move when turned by the gear on the side all though they sem a little stiff.
Any help appreciatted :bang:

 

B

bereal

Member

Aug 31, 2004

24

0

• Jul 3, 2005

• #2

Jetting

I don't know your altitude or air temp but it sounds like you are running way to rich. Try dropping the needle one position, going to a 40 pilot, and a 140 main. Do a plug chop to make sure you don't go over board. That's how I've my 220 and my brothers 220 set up and it is very crisp throughout the throttle range.

Eric

 

Y

yzfjim750

Member

Mar 12, 2004

21

0

• Jul 3, 2005

• Thread starter
• #3

Carb size

Hi bereal, I dont undserstand how I can drop the main jet size as I did a WOT plug chop and it was bang on, if I drop from the 152 to a 140 im pretty sure it will sieze.
My altitude is around the 100' above sea level with a temp around 23 degrees celcius.
I will give it a go, by the way does your 220 have a 200 carb on or the std 33mm???

 

R

Rhodester

Member

May 17, 2003

549

0

• Jul 3, 2005

• #4

Your jetting sounds good. Put the air box lid back on and give it another try. If that doesn't clear things up experiment with the choke when riding it though the trouble spot. If it cleans up with the choke on then you need to try richening that circuit (based on throttle position not RPMs). Where is your air screw set? Are you running aftermarket reeds? I'm very familiar with your problem...I had it. A different needle profile may be in order. My KDX is the 'H' version (with a 35mm carb)...there may be some differences. Let us know how your experimenting goes.

 

H

Humai

LIFETIME SPONSOR

Feb 6, 2000

199

0

• Jul 3, 2005

• #5

Jim,

Which slide are you running in that carb. Are you running the #5 slide as supplied with the original carb?

I found that the KDX220 ran way too rich just off idle with the stock #5 slide that came with the bike's 33mm carb.

I installed a 35mm carb with a leaner #6 slide which greatly smoothed out the low throttle jetting. I'd also install the stock H series KDX 200 (not 220) needle as a starting point - I'm sorry I can't remember the needle ID as I sold the bike years ago.

Your main and pilot numbers look pretty close. If I were you I'd be reluctant to go leaner than a 152 main without very close analysis via plug cuts.

 

Y

yzfjim750

Member

Mar 12, 2004

21

0

• Jul 4, 2005

• Thread starter
• #6

Hi humai, I have the original needle I think its 1174 installed in the carb with a #6 slide a 42 pilot jet, airscrew 1.5 turns out idled cleanest and fastest at this setting along with the 152 main, I have tried a 155 main with no noticable difference aso tried a 48 pilot jet with no noticeable difference, I put the arbox lid back on as advised by Rhodster with the snorkel removed and ten X 10mm holes drilled in top of lid with no difference!
It is a 35mm carb off a 200 KDX not the 33mm of the 220
I have been on the just KDX pages and I seem to be about right to his starting point.
The bike flies once it has cleared its throat but as soon as you slow down for more technical stuff the bike has to clear its thoat befor it revs freely again but once it has it flies.
Would sticking kips valvwes cause this if they were opening too slowly as they do seem a little to stiff bt they do all open and close???
Please keep the help coming as this is spoiling an other wise good bike. :bang:

 

H

Humai

LIFETIME SPONSOR

Feb 6, 2000

199

0

• Jul 4, 2005

• #7

From what you've documented, we may assume that the top end jetting is pretty close and the powervalve is at least opening correctly.

The symptoms of the powervalve not closing correctly is no low end power and a lean bog when the throttle's slammed open at low revs. You also notice when the powervalve is stuck open that the exhaust noise at idle is greater than is normal.

Here's a test to determine how close your idle setting is: Start and warm her up then let her idle. Turn the gas petcock off and let it sit until it runs out of gas. If the bike starts revving up and wailing just before it runs out, the idle is way too rich.

As a rough guide on the Keihin PWK, the pilot jet should be sized to allow correct idle mixture to be attained with the air screw at about one and a half turns out from completely closed.

 

Y

yzfjim750

Member

Mar 12, 2004

21

0

• Jul 4, 2005

• Thread starter
• #8

Many thanks

Just had the best ride on my bike yet ( two wheeled variety )
I ended up dropping the needle to the lowest position to lean the mixture at the bottom/mid range, left the 42 pilot and 152 main with the airbox lid on as described earlir in my posting and hey presto the bike after riding slow can now take full throttle from way out the power band and pulls like a good 'un until the kips valves open and then she flies, no hesitation, no flat spots just a lovely progressive pull from nowhere rite to peak power.
Thanks to all you guys for the help.

Now it is sorted I have changed my mind and I am going to keep the KDX as I was going to sell it and get a cr250
:)

 

G

G. Gearloose

Pigment of ur imagination

Jul 24, 2000

709

0

• Jul 5, 2005

• #9

Score a CGK needle and you will like the bike even better; start 2nd clip from the top. Use a 38 or 40 pilot with the CGK. Set the Air screw for best off-idle responce under load. Also check the reeds for flatness.

 

Y

yzfjim750

Member

Mar 12, 2004

21

0

• Jul 5, 2005

• Thread starter
• #10

Is it the rite size

Hi gearloose,
Is that needle for the 33mm on the KDX220 as mine is running the 35mm from a KDX200.
Well pleased with the bike now next thing will be reeds.
Thanks
Jim

 

G

G. Gearloose

Pigment of ur imagination

Jul 24, 2000

709

0

• Jul 5, 2005

• #11

Nope, its superior for '89-94 200's, 35mm, #6 slide.