My bike is idling erratically all of a sudden, what could it be?

[rosscopeeko]

I need a little help with my 03 cr250. I was out on a ride yesterday with a friend primarily riding woods and a little track through some woop sections. The weather was fairly humid compared to normal and the temperature was cool. Towards the end of the ride my bikes idle would surge up fairly high when we would stop. Sometimes it would come down after 10 seconds or so, sometimes it wouldn't. It would also start to rev when i would crank the bars to the side on a hill when i wouldn't make it. My friend say's he thinks it's running lean because of the change in the weather. He said that a slightly lean condition will cause the idle to flutter around. The bike ran rich before, not much spooge, but would load up if i wasn't on the pipe regularily. I just ordered a jd jetting kit last night, but have a ride on Saturday planned with a bunch of friends. Where should i look? Throttle cable routing? Jetting change? The bike is a relatively low hour cr250, approx. 30 hours all stock. Thanks,

 

[RM_guy]

Your friend is probably right. If the temp drops the bike will run leaner. You can usually get away with just closing your air screw 1/4 turn clockwise. That will richen up the pilot and stop the surging. Experiment with the extremes of the screw adjustment until it runs crisp off idle. I carry a small screw driver in my crossbar pad just for these fine adjustments on the trail.

Unless the temps change radically you don't have to touch the needle or main jet...unless you are the type that has to have the jetting spot on, all the time!

 

[keithb7]

In addition to the lean jetting symptom, have a look at the throttle cable routing. Sounds like maybe you are pulling the throttle open slightly when you crank the bars.

 

[IndyMX]

In addition to the lean jetting symptom, have a look at the throttle cable routing. Sounds like maybe you are pulling the throttle open slightly when you crank the bars.

Had that exact same thing happen to me, except it was the clutch cable that was having issues.. .when I would turn a tight right corner, I'd get a false neutral.. Thought something serious was going wrong with the gearbox.. Then I noticed that the clutch fork on the gearbox was moving when I moved the bars... DOH!