I've seen faulty plug wires come and go in a way similar to what you
describe at certain RPM's. I'd try a basic ignition tune up(plugs,
wires, rotor, cap), and if you have points change the points and
condensor. You can usually see the spot in the wire that is bad if it
is a defective ignition lead. The rubber around the bad portion of the
lead will usually turn white and sometimes swell up appreciably.
Another possibility is a defective ignition coil, you can put an ohm
meter on it and try tapping on the coil with the plastic handle of a
screwdriver a bit. If you see the meter moving around I would suggest
replacing the coil.

I've worked on a couple hondas with intermittent ignitions, mostly
early 90's models...in every case I just replaced the distributor with
an overhauled unit and the problem was solved.

Chris