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00 kx250 Stuck wide open on cold start.....sometimes.

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Well, replacing the reeds fixed one starting problem for me (4 million kicks to start it),  unfortunately it didn't fix the other, (my fingers were crossed).  Anyways once in a while when I first start it for the day, maybe 2 in 10 times,  instead of idling as normal it gets stuck wide open.  It doesn't seem to matter what I do with the throttle, wiggle it jiggle it swear at it smack it or twist it.  The only way to make it stop is to either shut it down and restart, or take the choke off.

Maybe I'm answering my own question, something screwy with the choke, but any ideas what the issue could be?  Vacuum leak, carb issue, idiot rider, wrong color powerband?

 

Thanks!

 

Oh and it did this before and after new reeds

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Well, replacing the reeds fixed one starting problem for me (4 million kicks to start it),  unfortunately it didn't fix the other, (my fingers were crossed).  Anyways once in a while when I first start it for the day, maybe 2 in 10 times,  instead of idling as normal it gets stuck wide open.  It doesn't seem to matter what I do with the throttle, wiggle it jiggle it swear at it smack it or twist it.  The only way to make it stop is to either shut it down and restart, or take the choke off.

Maybe I'm answering my own question, something screwy with the choke, but any ideas what the issue could be?  Vacuum leak, carb issue, idiot rider, wrong color powerband?

 

Thanks!

 

Oh and it did this before and after new reeds

 

 

 

is it the throttle itself getting stuck open? or no?  If not you pretty much answered your question. Check the intake boot for cracks, holes, check the gasket, the choke might be leaking too.  Tho running at WOT I would think it would be a little harder to start?  How many kicks after the new reeds? 

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New reeds one kick everytime.... so I'll put in a psychedelic purple powerband then.

But its not the throttle itself for sure.

 

 

Does it only do it when the choke is on?  Or anytime?  An air leak would only really be noticeable at idle/low throttle IIRC.  Wait for someone who knows more to chime in lol. 

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I believe an air leak will cause it to go WFO upon start up. In the airbox, I think.

Edit: somewhere between the air filter and carb I mean. Usually just a pin size hole.

 

Reed cage gasket, intake boot, carb itself maybe the choke. About the only places it can leak air, in that area. Other places could be a problem, maybe bad crank seal?  Hope not tho....  Get it to run, then spray carb cleaner around.. if it starts to die off when you're spraying it in an area, then you've found your leak.

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Flick the choke off as soon as it starts... Mine have always done this. It's the fast idle, not really stuck wide open just partial.

 

 

That screaming rev during cold start-up is usually an indicator of a too-rich pilot circuit.

 

 

Fix the rich pilot circuit jetting. The screaming cold-start-up will stop.

 

When the pilot circuit is too rich, the engine doesn't want to idle correctly, and people (unknowingly) compensate by turning the idle screw in. This results in the slide being raised up high enough that air begins to flow through the main cutaway rather than through the much smaller idle cutaway. Extra air plus the extra fuel from the choke means a screaming idle.

 

Fixing the rich pilot circuit allows the idle screw to be set back down where it should be, and the bike will then only idle at a slightly fast idle with the choke on like it should.

Edited by Chokey

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And fixing the pilot circuit involves.....?  I assume just a new smaller pilot jet..... I might even have a few of those.

Flicking the choke off and on again while warming up does "stop" the issue.  I'd rather eliminate it.

Edited by Greenmachine62

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My friends 93 kx125 and my 95 kx250 both do that on occasion. It's normal. Just shut the choke off right after it starts.

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