Motorcycle Repair: coughing carbs, honda cb900c, vacuum leaks

Question
I have a 1980 honda cb900c 45,000 miles I ride all the time usually 2 tanks of gas on weekends (top octane shell)---it has developed some coughing in the carbs or carb?? below 2000 rpm above that I don't notice--still runs real strong--any idea??---thanks for any help---oh --and it idles a little rough

Answer
Bill,

Sounds like a lean fuel problem at low speed.
-could be some water in the fuel or some dirt in
a carb idle jet.
-I think there is an air cutoff
valve on the left carb, these have diaphragms
to richen the fuel on deceleration. Could be faulty.

-Check your plugs and see what color they are,
if they look dark you
may be able to run the next hotter range spark
plug NGK(7) on a higher mileage engine. New plugs lately?

-Check for any air or vacuum leaks around the
intake.

-A carb sync may help to smooth the idle.
-Has valve clearance been checked lately?
could be a tight valve or leaking intake valve,
try a compression check.