starter valves sounds about right.yep activated by the wax unit.i think they restrict air,hence runs rich when cold.once the wax unit heats up the starter valves,or what i called plungers move back letting more air through.not sure what caused one on my bike to stick.i had shipped it back from europe and when i picked it up from the shippers depot it was running like a pig.took me a while to find out why but eventually tracked it down to one of the starter valves not opening when warm.i had a post on here back then asking for any ideas what what causing the rough running and sooty plug.will have a look for it.found it
http://www.cbr1100xx.org/forums/index.php?/topic/73866-running-rich-in-no-4-cylinder/