Why dont i get top end power out of my 1973 Honda cb750k Four?

Had it been used a lot in the past?If yes,that means that most engine parts underperform because of the age of the bike.Because this bike is more than 30 years old,its usual to receive reduced performance.Go to a dealership and ask what can be done.I think your bike needs an engine overhaul,and in general,lots of maintenance.This is going to be pricey!