Like the guys above said on those carbs: check in the bowls first for bits of rust. Also check the petcock's bowl and the screen inside there, clean and reassemble. When installing that petcock bowl, be sure to wet the O-ring first with a bit of grease or oil or spit, so it doesn't split when you are tightening the little bowl back on: it is old now. Or, get a new one...the air screws should all be set at 1 turn out from all the way in. Don't tighten these screws hard: the seats are soft aluminum or brass and this will damage those seats.
Idling at 3000 RPM is usually an indication of too advanced ignition timing. This is common with Dyna "S" triggers, because their installation manual is pretty vague. If you don't know how to use a voltmeter, this situation can get worse, and might be what the previous owner did for you...when it does run, check the timing first thing, using a timing light. It must be resting on the "F" marks for each pair of cylinders when idling at 1200 RPM or less, and must not pass beyond the advance marks for those cylinders when at 3000 RPM. The gap between the magnet on the points advancer and the face of each trigger should be in the range of .025" to .040", and should be the same for both sides, for starters. I've found .035" works pretty well for starting the process.
Idling at 3000 RPM can also be vacuum leaks in the hoses where the carbs attach to the engine. Make sure you don't have leaks here: one good method, since the hoses are old, is to go and get wider hose clamps and install those instead, and tight. The Honda clamps stretch out when they are old, and they cannot pull the old hose rubber closed. On a K2, it's time for new hoses, unless the previous owner replaced them. They will probably be leaking now, since you pulled off the carbs and probably still have the original, narrow, Honda hose clamps: this will not seal.
