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KTM 125SX Idle Problem

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Hello members of ThumperTalk!,

 

I am sorry if this topic is in the wrong area of the forum, I'm new! :)

 

 

Basically as stated by the title my 03 KTM 125SX when I do a Cold-Start on her she seems to Idle extremely loud and possibly high RPM's. I have done some research and some people are saying that it could be a stuck throttle cable that won't roll off or the choke on my kehlin carburetor isn't sealed properly. I am wondering what your thoughts are and what should I try first? This is my first bike however I seem to be mechanically minded so that should help me to understand the issues of my bike. So what should I try first to fix the issue? Side note: The guy I bought the bike off has recently put a new throttle cable on and I have the old one in a bag of parts he threw in for me like a gasket rebuild kit etc..

 

Also upon riding my bike for the first couple times when the bike got hot when I shut her off for a minute or so she wouldn't fire back up again until stone cold when I got home and off loaded the bike. Is this to do with the CDI? If so how much could my local dirtbike shop charge for a new replacement unit?

 

 

I'll answer as many questions needed to sort these two issues :)

 

Thanks, Brad.

 

 

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Just to add I know about how to adjust my bikes idle and it was idling perfect before and know has changed and I don't know why.

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Another thing to add is there is loads of oil coming out of my silencer. I will repackage it soon also as its burn to a crisp from the previous owner but still didn't sound this loud now. I am mixing to the ratio the previous owner told me but I have no clue what fuel he was using so yeah.. I recently put a brand new batch of fuel in the bike. I use Castrol's Racing Two Stroke Oil as there is hardly any smoke out of the exhaust even at a Cold-Start. Before the old mix used to smoke a lot tho.

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the high idle at first start when cold with the choke is common for a used KTM. I just turn the choke off as soon as possible-meaning when the bike will run without it on

 

BUT, it sounds like there is something else wrong now since the idle is gone and it wont restart when hot

 

on the restart, have you tried holding throttle wide open when kicking or tried choke on with throttle closed?

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I have tried it with choke but not with the throttle open wide. But I am only talking but the idle as a 2 Stroke sounds like Ring Ding Ding Ding Ding. My bike now sounds like its gonna blow up as she goes like Ring dang daang daaaang.

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My kx125 did that when my crank seals started to leak, but I would first try going over the intake boot screws and such to make sure they are tight and then check for an air leak with starting fluid. Does your gear oil level drop while riding?

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Also my carburetor actually has a pull n prime choke so it plugs back down so yiu only lift once or twice to choke the engine.

 

not sure what your saying.You don’t have a primer on your bike. You pull up the choke start your bike and push it back down. A choke pulls up and clicks into place. It only goes back down when you push it down. If it doesn’t work that way your choke is worn out. BTW I would almost guarantee you have jetting issues.

Edited by 91kdx25088

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I don't believe I am looking oil while riding I only seem to get oil to leak out of the exhaust a little bit before the expansion chamber meets the exhaust port. However I have been seeing black oil leak elsewhere on my bike without me even using it.

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