I'm having some sputtering or missing at 1/4 throttle to 1/2 throttle. Bike is fine when I twist it out as well as at idle. Inbetween is the issue. Normally this would suggest needle position, and perhaps a rich condition. I've installed a Yost air fuel mix screw, and have tried to "lean it out" with that. This only ends up depriving me of top end power and overall acceleration.. Not helping with the midrange sputtering.

This is all fairly frustrating as I don't like to have the bike pinned out all the time, but the last few rides have been as such to get past the unpleasant noise coming from the muffler.

I'm at sea level, with the stock air filter and a FMF powercore 4 muffler. 38 pilot, dj needle on third clip position, and 124 main jet. I seem to have lost some top end speed going from the 128 main to the 124. I initially thought the bog out was from the main being too rich but it seems that I was incorrect as the problem continues.

Anyways I'm just wondering if putting the needle at the second clip position would be too lean for my set up.

 

I'm having very similar issues!! Lots of good advice in my thread. Here is the link!

https://www.kawasakiforums.com/forum...-tuning-42182/

I should say though, I had bad stuttering once when I reassembled the carb and one of the shims fell off the needle and was holding it open. So never hurts to go back and check but I can tell you from experience a 124 is too lean. That's what I tried at 6000' and it was ALMOST perfect. I had to go one step smaller to get perfect.

Good luck!