i just got my cb450 running pretty good (basket case when i got it). i rebuilt the carbs with K&L kits, set the floats at 14mm, set the IMS at 1.5 turns out, installed new throttle cables, new clutch cable, cleaned and gapped plugs, made and installed new intake gaskets (rubber boots look good, new battery, disassembled the automatic timiing advance, cleaned it, lubed it and put it back together (might need to springs) and i adjusted the valve clearences. what i havent done is set the ignition timing, adjust the points, put air filters on it(the old ones are shot), and it still has the same plugs, plug wires, and spark caps on it that were there when i bought it. now it starts right up (with the choke off). it runs smooth, and revs up fast, but it doesnt decelerate like i think it should. most of the time it will bring itself down to about 2500-3500 rpm. sometimes it will just hover for a second and come back down to 800-900rpm (using mech. tach.). i tried adjusting the idle mixture screws but the are unresponsive on both carbs. i also checked for vacuum leaks by spraying carb cleaner all over the boots and gaskets. it also has slim fuel filters on both fuel lines with see through Tygon fuel line, and i can see the line full of fuel. but on a good note the bike screams!! its just i dont want to overheat because of this high idle/deceleration thing.