Re: question on Air Cut off Valves
Welcome here, Jim!
Air cutoffs typically seve to avoid popping when you release the throttle at some rpm. However stock setup CB650's were never observed to pop in this situation so Honda skipped them for most PD carbs and did not do the drilling there.
So you don't really need them and if you find a secure way to block the passages it is probably the better way to avoid separating carbs again in the next few decades...
Also carb rebuild kits that don't include them are typically cheaper and moreover much easier to find.
And maybe someone should mention you should clean out your tank, too.