i'm starting to develop something similar but it goes like a cut cat when cold but when it warms up it gets a surge around 3000rpm when driven light-moderately but sink the boot in and take each gear around ot 4500rpm you wouldn't notice the problem but just driving normally with some slight hills and it surges / miss / chugs.\
i have replaced coil, plugs, leads, rotor, coil condenser and gone to town with carby cleaner and nothing has changed.
when i was using the carby cleaner i was looking down the bore of the secondaries and noticed they didn't seem to budge when i gave it a boot full, is this normal?