'72 CB350 choke problem

[seank37]

I'm having a problem with my CB350. The choke won't stay closed when riding. I'm not sure if it's rattling open from vibration or from airflow. Either way, when riding, the choke comes open to the point where my bike starts to struggle. I can reach down and close it and everything is fine until it happens again. I'm not sure what is going on. My Clymers manual doesn't mention any choke adjustments, and neither does Google. Anybody have any ideas? I've resisted the urge so far to secure it closed, but it's really beginning to get on my nerves.

[Gravel]

shouldn't there be a set screw that can be tightened? I'd have to look at my bike to be certain.

[Gravel]

I checked my 76 400f and there is a nut that holds the contraption on/together. how tight is it?