Motorcycle Repair: 1973 honda cb500 four - rich-hotshift problem, 1973 honda cb500, vernier caliper

Question
I have recentlly aquired a 73 cb 500four, extensivlly cleaned carbs, (I'm an auto mechanic) needle valves and floats ok, set float height to manual spec, bike runns rich, black smoke no matter how much I lean out the carbs,it doesn't if it's running out of fuel, so would you lower the floats more than spec to correct the problem? Air filter plugs timming, tappet adjustment, timming chain adjustment,  points, all good, needle valves sealing, float height set with vernier caliper. Another problem, doesn't like to shift when hot, hard to find neutral, clutch problem or adjustment maybe? Thank you very much for your time, I have the original shop manual for the bike, thanks again

Answer
I'll answer the easy one first.  The shift problem is the clutch dragging.  It could be adjustment or warped plates.  To adjust the clutch, loosen the lock screw turn the set screw all the way counter clockwise until you feel some resistance to take out all the slack in the system and turn it in 1/8- 1/4 turn and lock down the nut to provide a little freeplay in the cable.  You should have about 1/8 inch of gap at the end of lever where it hinges to the mount before you feel resistance in the cable when it adjusted correctly.

Does the bike only smoke at idle or at full throttle?  The bike is getting too much fuel or too little air.  Check the air intake under the seat to make sure it's not getting covered up with something when you are riding.  I had a guy that complained about a tune up I did for him and after the third attempt to make it right, I happen to see him pull his riding gloves out from under the seat as he was about to leave it again.  That will cause the problem you are describing.

The only other thing left is the float level adjustment you described. The float adjustment can be tricky. Not sure just how you are adjusting the float but if you use the wrong reference point, you will set the floats 3 mm too high.  You need to use the rim of the carb as the reference point and not the gasket seat.  I like to turn the carbs right side up and hook it up to the fuel line and see just where the fuel actually shuts off as I'm adjusting the float levels.  Sometimes it hard to see just when the needle touches the seat with enough force to shut the fuel off.   

Good Luck,
Rich