KDXRIDER.NET

Issue> stall at idle & sputter at low RPM, runs smooth in upper range

Troubleshooting & Results>
1. ran compression test & was near bottom of operating range (122 psi), installed used rings off eBay & got modest improvement in compression (133 psi)
2. thoroughly cleaned carb & installed new jets (stock size), needle is good, float/needle good
3. thoroughly cleaned air box & installed new filter
4. installed new plug
5. examined piston & cylinder, no significant wear
6. examined reed block/reeds, no issues
7. checked for air inleakage on intake side found nothing wrong
8. found exhaust gasket/rings degraded/gone so it has moderate exhaust leak between head & pipe (ordered parts...TBD after install if that helps issue)

Any suggestions what else can cause the stall/studder issue??
Thanks!

Did you replace the pilot jet?
Other things to look at are float height, throttle cable, petcock and vent tubes.

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Replaced pilot jet, replaced petcock, installed new fuel lines, removed & lubricated throttle cable. Did not check vent tubing, from memory there are 2 lines....will pull those & check. Not sure about float height, it's not adjustable that I can tell; no bendable tang like on my CRF450R. My exhaust gssket/O-rings arrive tomorrow as well. Thanks for tips, I'll keep chasing till it's solved.

Never seen a non-adjustable float.

Can't wait to see this one once you get it sorted out!

To eliminate the carb as the issue, fit a carb of another bike and see what it's like.

... installed used rings ...

Why used?

1980 KDX400-A2 wrote:

... installed used rings ...

Why used?

Because that's all he could locate as OE rings (and aftermarket) are no longer produced.

I could be completely wrong, but it would seem to me that newer kdx rings would work. The bore and design should be similar, no?

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The ring end shape may be different? Different ID? ring actually thicker, taller??

6 Riders wrote:I could be completely wrong, but it would seem to me that newer kdx rings would work. The bore and design should be similar, no?

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That's what I originally thought as well. I'll let TigerKDX200 ring in with the details but long story short, he spoke with a Wiseco individual who stated it would not work and gave specific details of why and the current options available.