Sounds like valves need adjusting. If you dont know how to work on cars i would find a shop to do it but if you are a little mechanically savy then its a easy repair. It literally only requires feeler gauges. Although since you are there its a good time to change spark plugs, wires, and valve cover gasket if its old. Either way some valvetrain noise is normal on honda b series. Mine sounds like the one in this link which you can hear when he revs it.