From the Hondaman post "Things that cause a ratty idle":
#4: carbon buildup on the intake valve guide and stem. When the assembly warms up and the guide opens up, the thing runs OK. Try running BG44K (1 ounce per tank of fuel) for a while, or pull the head to check it out. (Bold is mine.)
BG products are available online. Did a nice job on one of my bikes.
Then do as Jerry Rxman suggested!