Depending on the model CB must have from 47 till 53 hp measured on the rear wheel. Perhaps the dealer has tuned the carbs in order to reduce horsepower. If the bike has it´s original muffler along with properly tuned carbs (main jets from 98 to 102)KEIHIN VP 02 and the original camshafts (not as "wild as the CBR 400 RR cams)it will work up to 13.000 rpm without coughing. A free-flow K&N air-filter along with a more opened silencer will work fine up to 58-60 Hp measured on the dyno. Mine is a CB 400 SF version R which pulls up to 13500 rpm and 210 km/h with almost 60 HP measured on the dyno.Also check out the electronic ignition unit to verify that´s the same with the original that Honda puts on it´s "good" models (Lucky Japanese fellows). If your dealer has special Ignition units that reduce HP try to buy a Japanese one that will work guaranteed.