'98 YZ125 Idling high

Firs Hello, I'm a noob to the forums, and this is my first adult owned dirt bike, so... go easy one me, lol, I'm not mechanically inclined but eager to learn. I recently got a 1998 YZ125 in decent shape, I knew it needed some TLC, so I've slowly been doing stuff to it, little hoses here and there, some missing parts, rebuilt the carb and adjusted floats right, etc...


This weekend I baptized it by taking out to a trail (BTW if anyone S. FL check out L-cross.com, killer place, a bit nasty and flooded right now, really friendly people) It was wet, slicker than cow poop (lol), some part of the trail were flooded, but had a blast, ran the bike once, did great, but I noticed the idle kept getting higher and higher, we got back to the trucks, rested for a bit, when I went to start it again the bike was idling high, not crazy it gona blow up high, but definitely noticeably high, any ideas why this would happen? specially since it was running fine before, Idle was a bit high anyways from the beginning, but not this high. Being a noob to dirt biking, not knowing much about these bikes, and no tools (I know, I know) I packed up and left.


While out there we noticed the exhaust joint had moved back a few inches and away from where it was supposed to be. not sure if relevant, but could this had affected it? even though we put it back where it's supposed to, bike still idling high.


And when I got the bike, the rubber boot that connects the air filter to the carb needs a metal clamp thing there, my buddy and I zipped tied it for the Sunday test run, just in case, but the previous owner was I can only assume had ran it without it, could this be part of the problem, leak, etc...?

Where should I start troubleshooting the problem?


Thanks in advance.


BTW: I got the Clymer's Repair Manual, to help me with my new toy.



Check that your throttle cable is not under tension, sometimes the cable is routed in a way that when you turn the handle bars it pulls the cable housing and therefore pulls the cable increasing your idle speed. Check this by removing all the zip ties and wiggling the cable with the bike running. Also check your idle speed adjustment screw and idle air screw. On older bikes the spring that puts tension on them can weaken and vibration will change their position. Replace that clamp on the air box boot, a zip tie will not seal it.

Like Burgershark said, check with the easy stuff first. If that doesn't cure it, you might have a slight air leak going on in the motor. If that is the case, you will need to fix it before you damage the engine.

Cool guys, thanks, I'll definitely check on these.


Tnx again.

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