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Poor Idle and starting

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I'm still having idle and a bit of hard starting on my '01 WR250. It was terrible when I bought it used and it is much better but I can't seem to get the idle to stabilize.

It idles fast then if I adjust it down, it drops to where it almost dies. It jumps up and down (using a tach to check also). It seems like it's still too lean and getting too much air at idle but I went from the stock 42 pilot jet to a 45 and now have a 48. It ran better yesterday at about 4000-4500 feet so it seems lean still, which it shouldn't be with this jetting.

I have the JD kit and it runs great except the idle and harder starting than normal when warm. I use the blue needle with 185 main and raised the needle a bit to richen it up since it was bogging (clip position 6).

First thing I thought was an air leak and I've replaced the intake boot between the carb and engine. I tightened both clamps so they are fine.

I've also adjusted the float level, replaced EVERY jet (guy had let it sit with gas and it varnished up and plugged at least one jet). Replaced the AP diaphragm, needle jet, cleaned carb very well.

Any ideas? Anywhere else there might be a common leak or some problem with the engine or exhaust that could also cause this? I'm about to the point to take it to the shop and see if they can figure it out.

Thanks.

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harder starting than normal when warm.

This is a typical symptom of an idle mixture that is too rich. A #48 pilot jet and clip #6 seem excessive too. What is the fuel screw set at?

Try stepping back down to a #45. Use the fuel screw to adjust, turning inwards should have the idle drop when the bike is warm, and then turning out for a steady idle. The smell of the exhaust should not be too strong of fuel or the idle mixture is rich.

There are 2 passages above the pilot jet that lead to the venturi. The first is directly above the jet, the second is directly above the fuel screw. There is a connector passage between these. Make sure these are all clean and the air jet passage that feeds the pilot jet.

You should be using the stock pilot air jet (#70?) if the air cut valve is unchanged. Closng the air cut passage would allow a YZ pilot air jet (#100).

Hope this helps,

James

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JD, thanks for the info. I actually never thought of it being too rich since I had a 45 pilot before. I'll drop back to that and mess with the idle screw some more.

It's possible since the old pilot jet was varnished up that the passages need cleaning like you said. I'll pull all the jets again along with the mixture screw and clean everything out again.

I'm running the stock air jets. I haven't looked at any of the lines coming out of the carb so I'll probably double check those as well.

After riding Hawaii Riders CRF250, I've decided I'm going for a new ride with electric start but I'm going to get this one jetted right before I sell it. It's close but not perfect. My wife thinks I'm crazy since I actually like doing this.

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