Stumbling at part throttle/low rpms

Two months ago my ‘04 Thruxton developed a stumbling when pulling away from a stop. After a few weeks of this, it began stumbling at part throttle low RPMs, when low speed cruising. When I open up the throttle to higher RPMs, it would stop stumbling. It idles fine and revs fine in neutral. I assumed it was carb related, so I pulled the carbs and gave them a good cleaning, including removing the jets, needles and pilot jets and all passages blown out with compressed air. Reinstalled everything and turned the pilot jets 2-1/2 turns. It didn’t help… still had the same stumbling problem. So, I installed a new Nology coil, new plug wires and new plugs. Still the same stumbling. So I pulled and cleaned the carbs once again, and installed new pilot and main jets with the same setup that I’ve been running for the last ten years… 42/140s. Still no help. So I replaced the vacuum caps and rubber intake boots. Still no help. I then had a valve adjustment done. Still no help. FYI, for the last ten years I’ve been running with air box removal, pod filters, 42/140 jets & BC Predator cans, then Cone engineering cans, with never an issue. The bike has 60k miles on it. I’m at my wits end. What am I missing? Could it be the pick-up coil or igniter? HELP!!!


Street Tracker
It wouldn't hurt to check that pick up coil gap. Or did you get it sorted already?