Motorcycle Repair: honda cb 900f, honda cb, pin holes

Question
i have a friends bike that im having problems with acceleration,it is a 1982 honda cb 900f,it accelerates slow and backfires an misses at around 4500-5500, and wont accelerate above that,any help would be appreciated.

Answer
You may still have a carb issue. The main jets or jet could be restricted  and causing it to not get fuel.Also its possible that a diaphragm and slide are sticking. The backfiring is usually caused by a lean condition,too much air and not enough fuel. Pull carbs off and go through tham carefully looking for varnish or green scale or even rust. Reset the floats and the mix screws then check the slides for pin holes in the diaphragm and whether they stick in the bore or move very easy. After that have the carbs syncronized to flow equally this should help.