KDXRIDER.NET

Did you install a new, fresh out of the box, spark plug?

Which plug is in it?

Tell us about the air filter.

Share your feelings with the group.

What if it was the power valve? How would i know? The part where the arm with the left handed thread attaches to will come out and go in the head easily. Could it do that and still be stuck?

You could disconnect the power valve completely and have a great running bike off idle through about 6000rpm.

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You said you tried a bigger pilot jet.... have you tried a smaller pilot jet?

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Jason wrote:Did you install a new, fresh out of the box, spark plug?

Which plug is in it?

Tell us about the air filter.

Share your feelings with the group.

New plug and filter. Plug is b9es

BamBam wrote:You said you tried a bigger pilot jet.... have you tried a smaller pilot jet?

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Originally had 48 then tried 45. Whats so confusing is sometimes it seems lean sometimes it seems rich. The air screw doesnt change anything either

Good that it is a new plug and filter. Unless you are in the desert or a fast rider, I think you will find an 8 will be the proper heat range for a 1989 - 1994 USA KDX200.

What is your altitude, humidity and temperature?

Have you checked the reeds?

Is the exhaust pipe or spark arrestor / silencer clogged??

EDIT: Are all grounds clean and secure?

berrymans is what destroyed my jet block gasket, for whatever it's worth.

Jason wrote:Good that it is a new plug and filter. Unless you are in the desert or a fast rider, I think you will find an 8 will be the proper heat range for a 1989 - 1994 USA KDX200.

What is your altitude, humidity and temperature?

Have you checked the reeds?

Is the exhaust pipe or spark arrestor / silencer clogged??

EDIT: Are all grounds clean and secure?

sea level, 50% humidity, 70 degrees. Reeds are good. Grounds are good. I think the pipe and silencer are good. I blew compressed air through them

I don't think it is a jetting issue then.

You said the air screw doesn't change anything? To be clear, are you saying when the air screw is turned all the way in closed, and then start turning the air screw out that there is no change in RPM at any point?

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BamBam wrote:You said the air screw doesn't change anything? To be clear, are you saying when the air screw is turned all the way in closed, and then start turning the air screw out that there is no change in RPM at any point?

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Correct

On Jetting alone, that sounds like textbook issue where pilot is too big. Because it's acting like the screw is all the way open even when closed.

Not to say there can't be some other problem, but I'd try a 42 pilot and repeat the air screw test.

It's a mystery with lots of moving parts (literally). Gotta start eliminating some variables.

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Well, you have a fuel delivery problem and have dipped your carb. As with everything else the remedy is simple but time consuming. Ensure your carb is both clean AND fully functional. In other words check the jet block gasket. Once it's all good and everything is mechanically sound, then follow the jetting guide step by step. Don't skip around, don't shortcut, just step by step and only change one thing at a time. The fact the AS does nothing is the first big indicator that your jetting is way off.

bufftester wrote:Well, you have a fuel delivery problem and have dipped your carb. As with everything else the remedy is simple but time consuming. Ensure your carb is both clean AND fully functional. In other words check the jet block gasket. Once it's all good and everything is mechanically sound, then follow the jetting guide step by step. Don't skip around, don't shortcut, just step by step and only change one thing at a time. The fact the AS does nothing is the first big indicator that your jetting is way off.

That just confuses me more because the majority of kdxs at sea level i read about is 155 and 45

Are you sure? When I was looking though the KDX jetting database, I would say that the majority of KDX200's are running 42 pilots... with the occasional one down to 40 or 38. The jetting guides say to turn airscrew out until RPMs drop and if its more than 3 turns to go up a pilot size. Yours does not change RPM at all, as if its already too large of a pilot.

Still seems weird to have that big of a bog, and not be really be all that far off in jetting. And I think there is something else wrong in the carb. But you gotta start somewhere, and a smaller pilot seems to be the most obvious next step. Never dig your heels in on jetting presumptions

BamBam wrote:Are you sure? When I was looking though the KDX jetting database, I would say that the majority of KDX200's are running 42 pilots... with the occasional one down to 40 or 38. The jetting guides say to turn airscrew out until RPMs drop and if its more than 3 turns to go up a pilot size. Yours does not change RPM at all, as if its already too large of a pilot.

Still seems weird to have that big of a bog, and not be really be all that far off in jetting. And I think there is something else wrong in the carb. But you gotta start somewhere, and a smaller pilot seems to be the most obvious next step. Never dig your heels in on jetting presumptions

Turning the air screw out (ccw) should raise the RPM. And if it's more than 3 turns you go down on pilot size.

With my bike, the air screw test suggests I use a 42 Pilot. The idle starts to raise at about 1.75 turns out. However, if I snap the throttle open it will quickly lean bog then rev. Air screw adjustments made it better, but it never went away until I put a 45 pilot in and raised the needle one slot. If I put my air box lid back on I can run the 42.

The Air Screw provides AIR to the idle circuit. If the idle does not increase, at all, when opening the screw, then the circuit is too lean already. Take the carb completely apart and replace the jet block gasket (jets r us has it), put the stock jets in it and start over.

And FYI, blowing compressed air into the pipe and/or spark arrestor will tell you nothing. That isn't enough volume to test anything.


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What is the difference between a lean bog and a rich bog?

nate9521 wrote:What is the difference between a lean bog and a rich bog?

Rich isn't really a bog. More of a spitter/hesitation/ have a hard time reving. A lean Bog is obvious. When mine did it, instead of the the typical 2 stroke bwaaaahhhh, it would go booooowahhhh. It's almost like the engine is trying to say the word "Bog"