Norton AMC Gearbox Overhaul with Mick Hemmings
Download the complete PDF version using the green download button at the top right of this page for a Classic Mechanics article covering the stripdown and rebuild of a Norton AMC four-speed gearbox with Norton specialist Mick Hemmings. The gearbox used in the feature is from a 1965 750cc Norton Atlas, but the article also applies broadly to Norton four-speed gearboxes from 1956 onward.
The article covers identification details for Norton AMC gearboxes, including pre-1962 and post-1962 shell markings, Commando gearbox lug differences and spacer washer notes. It then walks through draining the gearbox, removing the outer cover, gear change parts, clutch operating parts, kickstart mechanism, sprocket, inner cover and gear cluster.
Later sections cover inspection of gears, selector forks, shafts, bushes, bearings, camplate, quadrant and gearbox shell. The rebuild notes include bearing replacement, camplate timing, quadrant setup, reassembly checks, oil recommendations and useful workshop advice from Mick Hemmings for avoiding common AMC gearbox problems.
Contents Include
- Norton AMC four-speed gearbox stripdown and rebuild
- Atlas, Commando, Dominator and related Norton gearbox coverage
- Gearbox identification markings and shell differences
- Outer cover, ratchet and gear change mechanism removal
- Clutch operating arm and kickstart shaft inspection
- Drive sprocket and mainshaft nut removal notes
- Gear cluster removal and inspection
- Selector fork, camplate and quadrant checks
- Bearing removal and replacement guidance
- Layshaft bearing upgrade notes
- Camplate timing and quadrant setup
- Rebuild tips and gearbox oil recommendations
