The needle adjuster is threaded. It took me a few weeks to realize this and I was trying to adjust the carb with the gas tank still on the bike. Turns out I was only richening the carb, and never leaning it out when I was making adjustments. To say the least it was frustrating. So I ended up JB welding the knob on so it will no longer spin. If any experts feel I've done a bad thing let me know, but so far I'm happy.