quite possible the dumbest question

ZKDX

~SPONSOR~

Aug 23, 2002

309

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• Oct 16, 2002

• #1

.......but i'm gonna ask it.. i always read where everyone is talking about adjusting the air screw. Well i'm not a carb genius, so where in the heck is the air screw...is this the same as the throttle stop screw?...please don't throw rocks at me just laugh.

 

D

dirt bike dave

Sponsoring Member

May 3, 2000

5,348

3

• Oct 16, 2002

• #2

It's not the same as the throttle stop screw. The air screw helps control the pilot or slow speed circuit, and can have a big effect on performance and throttle response below 1/2 throttle. Changes will often effect idle speed.

Turn it in to richen, out to lean. As a general rule, if the bike runs better with the air screw two or more turns out, you should go down a size on the pilot jet.

On most carbs, the air screw is located on the left side of the bike, low down on the carb near the rear, above the float bowl. It is a brass screw, usually only a small screw driver will fit.

 

ZKDX

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Aug 23, 2002

309

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• Oct 16, 2002

• Thread starter
• #3

is it possible that my 87 kdx 200 doesn't have one...i swear i can't remember seeing a screw other than the throttle stop screw....i'm at work so i can't back that up...oh wait let me go to kaw.com and check that parts diagram again....

 

ZKDX

~SPONSOR~

Aug 23, 2002

309

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• Oct 16, 2002

• Thread starter
• #4

ok...just checked parts diagram....i really don't have an air screw, what's up with that?!

 

D

dirt bike dave

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May 3, 2000

5,348

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• Oct 16, 2002

• #5

I'm not familiar with the '87, but all the bikes I've owned including 3 KDXs had it locatd as described above. I looked at the '87 diagram at buykawasaki and there is no air screw shown, but you can see a spot where it should be.

For comparision, look at the carb diagram for the '90 KDX 200 - the air screw is labelled and you can see where it goes. When you get home, look for a small screw at that location on your carb.

 

ZKDX

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Aug 23, 2002

309

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• Oct 16, 2002

• Thread starter
• #6

so if i really don't have one...what does this mean...that the air mixture is pre-set?

 

D

dirt bike dave

Sponsoring Member

May 3, 2000

5,348

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• Oct 16, 2002

• #7

There are optional slow speed jets (aka pilot jet) for your bike, so if you truly do not have an air screw, you could change the pilot jet itself to tune the carb.

Hopefully, you do have an airscrew adjustment, as it is very useful for fine tuning and it is easily adjusted without having to dis-assemble anything.

Besides the air screw, the jet needle and slide cutaway also have a big impact on low speed running, so changing or modifying these items is another way of fine tuning the carb. Older carbs such as yours have both a jet needle and a needle jet.

Here is a link with an overview of jetting. There is one section explaining which features effect which part of the rpm range.

http://ericgorr.com/techarticles/carbtuning.html

Hopefully, someone with your model bike can confirm or deny the existence of the airscrew.

 

Last edited: Oct 16, 2002

C

canyncarvr

~SPONSOR~

Oct 14, 1999

4,005

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• Oct 16, 2002

• #8

How clean is your carb?

It's not hiding under the dirt, is it? ;)

Not all carbs have air screws. As I recall my daughter's sportrak90 doesn't. That's not exactly a performance machine.

BTW...just to make things more difficult, some carbs have FUEL screws. They operate oppositely from AIR screws in that it's turn OUT to richen, IN to lean.

Fuel screws are usually DOWNstream, air screws usually UPstream (down is PAST the carb body in the direction of airflow, UP is before the carb body in the direction of airflow).

Then there's my wife's mikuni equipped yamaha warrior. It has a DOWNstream AIR screw.

Just to keep things interesting.

 

D

dirtryder72

Member

Jul 24, 2002

40

0

• Oct 16, 2002

• #9

i have a 87 kdx and im looking at the service manual as i write...there is no air fuel mixture screw but there is an idle adjust screw...im guessing you have to mess with the jets for the air fuel mixture

 

ZKDX

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Aug 23, 2002

309

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• Oct 17, 2002

• Thread starter
• #10

as dirtryder said i confirmed last night that i DO NOT have an air screw. Hmmm, maybe i wasn't as dumb as i thought. And yes my carb is very clean, that's one thing i always make sure of, but i have done absolutely no jetting yet, but if you've seen some of my other posts you'll see i'm currently battling some electrical problems which prevent my starting of the machine :(

 

J

JasonWho

Member

Apr 10, 2002

2,109

0

• Oct 17, 2002

• #11

---

 

Last edited: Sep 18, 2004

ZKDX

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Aug 23, 2002

309

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• Oct 17, 2002

• Thread starter
• #12

no still no fire...i've checked my resistance till i can check no more, i believe the stator did check out of tolerance last night, i'm taking my coil today to have someone else double check it, then i guess i'll order the stator first

 

D

dirt bike dave

Sponsoring Member

May 3, 2000

5,348

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• Oct 17, 2002

• #13

Haven't seen your other threads, but stator failure is pretty common on the older KDXs. Usually the bike gets harder and harder to start until you can't get it running at all.

You can have your existing stator rewound. There are some specialty shops that handle this if you send them your stator. It isn't exactly rocket science, so a repair shop near you may be able to take it on. I think C'Dave rewound his own- you might find an old thread on that.