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how to make my 1999rm 125 idle

Joined
May 21, 2007
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#1
hey i just got my bike worked on we got it to start and everything but no matter what i do i cant get it to idle maybe theres something you guys can tell me that will fix it anything will help thanks
 
Joined
Jan 14, 2007
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#2
maybe your pilot is to small or too big does it load up easy or have a hanging idle meaning the pilot is too small what is you air screw at 1.5 out from the closed pos. seems to work pretty well. it is effective between about a 1 to 2 1/2 then it is time to change your pilot. try a new plug. and always use fresh gas wheather it is from the pump or race fuel.
 
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May 21, 2007
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#3
which one is the pilot ive tried to work on it and just cant get it is the air screw the plastic one or the metal one if to i got the metal one turned out about 1 1/2 or 2 turnsbut im not sure about the plastic one
 
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May 21, 2007
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#5
i finally got it to idle now it just fowls plugs way to easy i think it might be because the gas is to lean or rich im running it about 32:1 but i thonk it should be different any tips??
 
Joined
Jun 3, 2007
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#6
I just had the same problem with my Yz250. i had to redo all the jetting. first off if your bike is breathing heavy your not getting enough air so switch to a smaller pilot jet. this will effect your 0 to 1/4 throttle so once you mess around with this it should idle. next let it idle and the shut it off and check the plug it should be a nice crisp brown if it is wet or black you are too rich so try raising the clip position on the needle to lean it out. if it is white do the exact opposite lower the clip position on the needle to richen it. this may take awhile so have patients. after you get it to idle properly and not to rich or lean ride it around and see how it pulls in 1/2 to 3/4 to full throttle if it pulls nice and smooth you probably have the right main jet. so after you ride it hard for a good 15 minutes stop and check the plug. if the plug is brown and crisp your main jet is correct. if its black and wet you need a smaller diameter main jet. if it is white or very light color go to a bigger main jet. remember this all takes time and patients so don't give up you can do it with a little bit of time and effort. also Marc Salvisberg has an excellent carb tunning page. google search him and go to his factory pro page. i know it's for bullet bikes but the same applies for dirt bikes the only difference is when he talks about the fuel mixture screw and how to get to this ignore it this is the air screw on regular keihin carbs. good luck.
 

IndyMX

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#7
2 stroke bikes aren't supposed to idle.

If you want it to run right, set it up so that you get about 10 seconds of idle.. These things are supposed to run at high RPM's, not at idle.
 

darringer

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Dec 2, 2001
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#8
2 stroke bikes aren't supposed to idle.
How many times does this have to be said? 2 strokes can and will idle just fine. Your jetting is off. The 99rm125 has a ridiculously rich pilot circuit. With the 39mm PWK that's stock on that bike, it came with I believe a 55 pilot. When I had mine I went all the way down into the low 40s on the pilot to get it to idle clean. Once jetted correctly, it will have good bottom end, for a 125, idle all day, and never foul plugs.
 
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#10
they arent meant to idle. sure you can crank up the idle screw until it idles, but they arent meant to idle.
 

darringer

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#11
Please tell why 2 strokes shouldn't idle. And what is the purpose of the idle speed screw if it's not for adjusting idle speed?