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Erratic Idle

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I bought an 04 TT-R 125 about a few weeks ago. It is pretty easy to start, but refuses to idle unless choked. I have adjusted the idle screw and changed the jets, but it still won't idle easily even after warming up for a few minutes. However, after riding the bike for 15 minutes or so it idles really high.

I am sure this has been talked about before, but I can't find it. Anybody have any ideas as to what might be causing this erratic idle.

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Do this by spraying WD 40 on the boot between the head and carb. If the idle changes, you have an air leak.

Could also be that the cable or throttle is sticking partially open, thus causing the carb to fail to return to idle position.

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I had this same problem that I just fixed on my DD's bike.. Everything was stock but had been messed with on the adjustments to try and get it to run better. It wouldn't idle unless very warm and you had to use the choke to start it all the time.

I finally decided to rebuild the carb and rejet it with JD Jet kit along with their needles. I also purchased an air screw that was long and had a handle on it so I could easily change that.

I tuned it for sea level with an open air box. I put a 125 main in, left the stock pilot jet but made sure it was perfectly clean since it is a very small hole that can get dirty (in fact, that could be your problem). On the stock air screw, I noticed JD kit provided a new o-ring to seal better and so did the new screw that I purchased. When I pulled the stock air screw, there was NO spring ?!?! So I don't know if it was lost at some time or what.

Anyhow, with everything put back together, I started it right up and the idle was VERY high because of where it was set to compensate for all the other problems.. I backed that out a turn and it purrs like a kitten now.

The moral of all this is to take it appart and have a close look at everything to make sure it is back together correctly and everything is adjusted right. It was like night and day in my case..

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