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Message: [QUOTE="reepicheep, post: 1373930, member: 104942"] Update! Well, I took the rebuilt KDX for the first long woods ride yesterday (where I was not chasing a 9 year old, and I could ride harder). Temps were in the 60's, a great day for riding. Significant jetting changes as a result. I would ride a few laps (maybe 10 miles of technical trail), then make an adjustment. Lesson #1... don't trust changes you make in your driveway. I thought I had let the bike properly warm up, and thought I was riding far enough to tell a difference, but my low speed jet was *way* off. So yesterday, I ran a lap with the 48 I had in there, and it was the same. Bogging at partial throttle openings. Swap to the 42 (because it was the only other one I had with me), and the thing ripped again. Still just a little bog at very low RPM's, but a much wider powerband, and the thing is a total wheelie machine now, even at partial throttle openings. (I was having a blast jumping off the top of dirt moguls climbing up hills... the KDX just leaps off of them if you keep it in the power band). So the lessons... 1) Don't trust samples from short data runs. 2) I don't think my "play with the air fuel screw" is a reliable way to tell if you are on the rich or lean side of the problem. Just swap the jets and make another run. 3) Don't get suckered into thinking "the slow jet controls low RPM, the fast jet controls high RPM". I keep slipping back into that thinking, and when I got the fast jet closer, I fooled myself into thinking the slow jet was better. The way it works is "slow jet controls 1/4 to 1/3 throttle opening behavior" and "fast jet controls wide open throttle" regardless of RPM (which I am sure isn't completely accurate either, but it's a more useful oversimplification ;) ). Wide open throttle feels pretty solid, up until I get over some magic RPM line and the engine starts breaking up. I need to get a tach on there to see if thats just as fast as my motor will go, or if thats a jetting issue. But for now the 160 feels pretty good, though I may try a 155. The 42 slow is running pretty well, but that seems scary lean to me. So for peace of mind, I'll probably drop in a 45 (which I have had trouble finding in stock locally) and see if it goes better. (the real lesson here is that if you want it jetted right, you really have to go find somebody with a dyno and a 4 gas analyzer... and that anything I am going to do on my own will probably get it jetted better over time, but never perfect...) [/QUOTE]

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