Why can't I sync my Bandit's carbs?

Q. I decided to sync the carbs on a 1999 Bandit 600 I just bought. I got her warmed up and tried to set the idle speed at 1750rpm for the sync (as per the Haynes manual).

I turned the adjuster screw but it wouldn't go above 1500rpm AND the screw moves around in a kind of arc (like a lever) instead of just turning on its screw axis.

Is this normal? Can't find any mention of it anywhere!
Maffp, mcn forums
 
A. It sounds like the thread has stripped on the adjuster screw or in the carb body. It's OK though, you can balance the carbs at 1500rpm and it won't make any difference. However, getting a new thread in the carb body could be tricky...