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Hold up, lol You asked about the STIC, not the STIC X. That's why I said the 55 is not a thing. You need to post in the Super X threads hear and on ktmtalk. So, 65+ pilots with the right air correction jet is where you want to be. Prolly have the 85 ACJ. If the model you have lacks the ACJ passage(std X), you adjust the AS out further for bigger pilots. Regarding the needle diameter selection. On the meter blocks, .0063"-ish orifice(tube exit) gap is the target. To mimic that with the X, you need to try...

Red and WJ needle are a pretty happy place. Not so much on the Mikuni's. Over on TT, search that STIC it...thread for crewjones. He contacted me on nearly the daily for over a year. He did rigorous proper testing, ie one change at a time and Apex domes were used. Those Mikuni needles, we didn't like those and you'll be chasing settings. UK guys liked them for their UK fuel, but they admit to soft on lug factor and rich at lower rpm range. Crew ended up with red and WJ dropped to 1clip, 52p and AS @ 2...

your pilot and main are too small imo. N3EJ is a super lean needle for a 125. The right combination of pilot to main jet is what needs to be achieved other wise STIC feels like a regular carb. JDjetting best dynos with n3ej needle came with a 215 main on the 300 ktm so a 125 is gonna need much richer which doesn't leave options. Did Stic send you a modified n3ej with the sanded tip?? If you just managed to tune the bog out you are probably still too lean to fully take advantage of the stic imo...

Looks like @dfree is getting it figured out. He posted this over on TT. Hey yall! I believe the problem was too lean. I ended up swapping the yellow N3EJ needle out with a purple N3WJ, I have it in the 2nd position. Went from a 195 main to a 205 main and went from a 50 pilot to a 55 pilot. She seems to be liking this set up. No more bogging off jumps and stuff. Might be a little to rich on the bottom, thinking of drop down to a 52 pilot this weekend to see if I...