Fuel, air, spark are the 3 things needed...so you're not getting something there.
Most of the misfire problems I have encountered have been ignition related. Coil, igniter, plugs, wires, etc. Another problem could be the ECU...but that is more rare.
All honda engines that I know of require a valve adjustment.
Try replacing the fuel filter...new tank of gas...etc. Cover the bases, you know what to do.