Running hot

[Brian VT]

My bike steams some coolant after longer climbs. I'd say that I'm at mid throttle during most of the climb. I'm moving at a decent speed so there's air moving through the (clean) radiators. It's fine when back on level terrain.
After a normal 30 mile ride, with some hills, the coolant level is an inch or two below the fins.
My 1st thought was that the cap (1.5) may have gone bad. I switched to the stock (1.2) and it was no worse and no better.
I looked at the (LTR) impeller and it looks fine and turns when I kick the starter.
My next thought was that I was lean (2nd clip slot, 178 main). My buddies said my exhaust is smokey and think I may be rich. My needle seat could be wearing/worn, too ?
I should have taken a plug reading after the hill but I figured it'd be better to just ride easy and keep some air moving over the radiators and coolant flowing.
It's an '03 EC300 with a fresh top end. The issue existed before the new top end. Oil has looked good at changes.