hi there. any pointers on this issue would be great. the facts: Bike: 1971 CB100 Great little commuter. Kicks first go, idles great and climbs to town speed adequately. Issue: At high revs the engine begins to hesitate/surge/miss etc. This can happen under load or whilst accelerating down hill. Please note, i would like to supply accurate RPM but the CB has no tacho. Actions taken so far: 1. New Spark plug 2. Cleaned Air filter 3. Drained carb, check for crud. she looked ok. cheers.