Some history - bike has new major tuneup - plugs, wires, valve adjustment. Carbs have been thoroughly cleaned on the bike and work great, except for idle. Bike has 21,000 miles and runs great, gets great mileage and will really move out, if pushed. There was a hesitation right off idle but the can of sea foam took care of that.
The idle is, well, weird. It seems to rumble. The tach cycles, running slower then faster in regular rithum. It seems to have a vacuum leak and, if it was a car, that's what I'd be checking.
I cleaned the vacuum valve that lets air into the exhaust. Of everything I see, that seems to be the one possibility that could cause a cycling, rumbling miss. Are those things known to go bad? What happens if you just disconnect it, and plug the vacuum line?
I'll bet somebody that has had a lot of experience with the concours can tell me what's wrong right away. I sure would appreciate it.
Oh, and can I get a brighter headlight bulb? What bulb should I buy?