That's the slide! As I said in last post, remove your cable and lube it. If it's beyond repair, renew and lube it. Re-route it back to the carbs, avoiding sharp bends. If you feel energetic, make sure your throttle is moving freely. You could also remove your carbs, you'll have to for a re-fresh anyway, and check the movement of the slides. Look for bright alloy on the slide, denoting high points, which you can ease down, and tears/rips in diaphragms, if fitted. And, as the carbs are off, dump them in the ultrasonic tank. On re-assembly remember....don't over tighten things. Most of them are either alloy or brass. They're so easy to strip/snap. Seeing as you're in the US, you could try FactoryPro for your spares?