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Rev high on start?

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#1
Hey,
Although its still winter here and i could be snowmobiling (but sled broke) i was thinking of dirtbiking and my plan for the summer. But one of my biggest concerns is when i first start the bike, it revs very very very high, so high that i usually apply the kill switch for a couple seconds to bring it back down, then it idles fine and runs fine. I always turn the little gas lever off after riding, but that doesent seem to help anyway.

Does anyone have any ideas to why its doing that?
Thanks in advance,
Andy
 
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#2
Does it continue to REV high after you open the choke ?

My 2 stroke does this as well there is an older Thread that covers this but I can't remember what it was called. I believe it is a lean condition that could be caused by an air leak somewhere. But if, when you open the chock everything settles down and all else seem OK then I wouldn't worry about it. Mine does this especially when it's cold.

Maybe someone smart can elaborate on this subject.

Cheers !!!

Steve (IT200)
 
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#3
It only does this before its warmed up, when i have the choke on... Right now the airfilter is pretty dirty so it would be running kind of rich anyways, but its bewildering :)
 
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#4
The choke is only for starting and should be turned off as soon as the bike starts on a 2 stroke. This it what I do and the high reving goes away. I understand your concern it is freaky when the bike revs up with no load.

Try turning the choke off right away and see if it keeps running.

It may have been in the Just KDX Forum, read through there it has a lot of good info that it valid on any 2 stroke.
 
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darringer

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#6
When I had my 99RM125, the pilot circuit was very rich. So to correct the problem, I switched to a 40 pilot. The bike ran extremely well from just off idle, but started the same way yours is now. This is because the pilot circuit is lean. It is only a problem in cold weather. You can go richer on the pilot circuit until the problem clears. But what happened to me was the bike started great, but then ran too rich. I never had any problems with the bike starting this way. I also turned the choke off immediately after it started.
 

kev_rm

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#7
same here with 99rm250 darringer, but turning in the air screw helped me start properly, and run the proper pilot for warmed-up conditions. Stock is 45 I'm running 38 now, thinking of going one more down.
 
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#8
I'd worry about cold seizing it. An air leak would rev out all the time, causeing detonation and the kill switch wouldn'd do anything. I would assume it would be a cause of the cold weather.
 
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#9
Yeah i do turn off the choke as soon as it starts, and it cant be the cold weather because it did this in the summer +33 or higher temps. I havent started it scince octoberish because it has been too cold to ride
 

merlinnn

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#10
Hi 1999Rm125,

I have the same problem with my yz, I asked the question on a different thread. My problem is not temp related as it is summer here now. The plug also appears to be showing a rich condition.

Any techs out there that can help??
 
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marcusgunby

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#11
The plug wont show a lean pilot setting-try one size larger pilot jet and be happy.
 
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#12
got the same issues has any one found the solution yet?
its not the cold must be the jetting or a air leak any idears?
 

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