Maintenance & Technical > KX500 Original
Jetting!!! Again and again and again!
gowen:
Cam, thanks for the idea! I have a 155 laying around, so I will give it a shot today. The surges are only in neutral. If I pop the throttle, it will rev, decrease then rev again, like as if I hit the throttle a few times. It does not do it in gear unless I pull in the clutch with some RPM's. Would you think the reeds could be the cause of this? I checked the reeds a little while back and it was a little opened. So I turned them around. Just a thought...
Thanks for the input and help, I'll give the 155 a shot later this afternoon.
KXcam22:
Gowen,
I have always wondered if the surging is caused by the vacuum the huge KX piston must make when you rev then chop the throttle. Mine does this a bit if I chop the throttle on downhills. Again not sure if it does it in neutral but maybe I'll fire it up in the backyard tonight and see. Possibly the vacuum is grabbing a gulp of air past/under the slide, maybe forcing the slide up a tad to grab some air? Total speculation on my part!! Your reeds should be ok as the engine intake vacuum/pressure pulses will force them to work even if the tips are a bit open. Not sure what your elevation is. I ride at 2000'-6000' and mine uses a 155. I ran a 158 for years (ran great) but the 155 is noticably smoother at 3/4 to full and still a touch rich. Cam.
gowen:
I just got back from riding with a 155. It is lightly raining here, so it was somewhat muggy. Anyway, you were right, I first warmed it up with the 158 rode it a little and did great. But, was very touchy/over sensitive in the mid range, which I was assuming a little lean. I came back to the garage and switched the 158 to the 155 and then richened the needle to the center notch. Which did wonders in the mid-top range. The surging has gone down, but is still existant.
Let me know if you are having the same issue. It is when the throttle is hit and chopped. It revs, decressed the rev then kinda pops and revs slightly a few times. It does it when I chop the throttle in gear and pull in the clutch too. I will try running a tank of pure C12 to see if it helps. I'm now mixed 50/50 pump/c12.
Thanks, it's coming together finally.
kawdude:
Those are the type of things I'm hearing. However, when slowing down in gear the bike d**n near jumps at every pop. It's annoying as hell and dangerous in the wet stuff.
To me if it's surging, the screw doesn't help but the needle does.. that seems to say that the circuit is lean. This may be related to the needle, clip position, main jet or float level. I know that I'm not helping.
It sounds close...I agree with Cam.
KXcam22:
Gabe,
Cool! Getting closer still. You might want to try raising the needle one more spot, to richen the 1/2 range and see if that helps further. Is the 1/8 to 1/2 throttle transition still smooth? That part is controlled by the straight section of the needle. With the 155, as an experiment it might not hurt to try the next richer needle with the needle lowered one spot from center to see how the bike reacts (richens the 1/4 but the 1/2 to full should stay about the same. Cam.
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