Norton Commando 750/850 Buying Guide: The Isolastic Truth
The Norton Commando (1967–1977) is the last great British parallel twin: fast, light, and smooth in a way no rigid-mounted twin of its era can match — when the rubber-mounted drivetrain is healthy. Most of what decides whether a Commando is a joy or a project is visible from the right side of the bike with the engine off. Here is the order to look in.
Know Which Commando You're Looking At
The Commando launched at Earls Court in 1967 with the 750 (745cc) Atlas-derived twin in a new frame, and the range ran a decade: Fastback first, then the Roadster (the common one), the Interstate with its big touring tank, the Hi-Rider, and the short-lived Production Racer. The 850 (828cc) arrived for 1973, and the Mk III of 1975 is the one most buyers actually want: electric start, left-foot gearshift, rear disc brake, and a quieter, more refined package. Engine and frame numbers should agree with the year the seller claims — Commando dating is well documented in the owners-club world, and a bike whose numbers don't support its story is priced wrong until proven otherwise.
The Isolastic System: The Whole Point, and the First Check
Norton's answer to twin vibration was the Isolastic: the engine, gearbox, and swingarm are rubber-mounted to the frame as one unit, adjustable by shims. When it's right, a Commando is genuinely smooth. When the rubber mounts wear or the clearance goes out of adjustment, the symptoms are unmistakable: a weave or wobble at speed, a bike that wanders mid-corner, vibration that wasn't there in the seller's description. Budget and attention, in that order: Isolastic wear is serviceable — mounts and shims are wear items, not a death sentence — but a Commando with tired Isolastics and an asking price that assumes they're perfect is two prices, not one.
Gearbox: The Bearing With a Reputation
The AMC four-speed box is strong, with one famous exception: the layshaft bearing. Its failure is the classic Commando gearbox story, and an upgraded bearing is the known preventive fix. On inspection: listen for gearbox whine that changes with load, check for sloppy shift action, and ask directly whether the bearing has been done. A seller who knows Commandos will know exactly what you're asking.
Engine and Primary
Cold-start it yourself. A healthy Commando twin starts without drama and settles; smoke that doesn't clear, top-end clatter that stays, and oil appearing at the primary chaincase joint are the usual tells. Commandos weep oil in the folk imagination more than they must in fact — a dry bike exists and is worth paying for, a wet one is worth less, and the difference should be negotiated, not discovered. Check primary chain adjustment access, clutch drag, and whether the charging system (points-era bikes often carry electronic ignition and alternator upgrades — good, if documented) actually charges at cruising revs.
Frame, Swingarm, and the Running Gear
Inspect the headstock area and frame rails for crash repair, check swingarm pivot play (it lives inside the Isolastic unit, so wear here compounds the handling story above), and budget honestly for fork seals, steering-head bearings, and wheel bearings on any bike that has sat. Disc brakes on later bikes and the Mk III's rear disc are a real usability gain; drum-brake early bikes stop like 1968, which is a riding-style decision, not a defect.
750 or 850?
The 850 gives up a little of the 750's rev-happy feel for torque, refinement, and — in Mk III form — the electric leg. Collectors argue; riders just buy the Mk III. Either is a fine motorcycle when the Isolastics and gearbox are right, and neither engine choice rescues a bike whose numbers, frame, or title are wrong. Which brings up the standing rule of this Journal: numbers first, stories last. Check the paperwork like you check the layshaft bearing.
Before the Money Moves
- Engine and frame numbers verified against the claimed year and model.
- Isolastic condition assessed — ridden at speed if the seller allows, shimmed-or-worn stated plainly.
- Layshaft bearing: done, documented, or priced as not done.
- Cold start witnessed; charging confirmed at cruise rpm.
- Primary case, headstock, and swingarm inspected with a light, not a hopeful glance.
- Title clean and in the seller's name.
The Commando's British-twin stablemate in our library is the Triumph Bonneville — the Bonneville guide shelf is where our British coverage starts, and the full guide index covers the rest of the shed. For the way we check any classic before money moves, the Ironhead Sportster buying guide and the BMW Airhead buying guide in this Journal run the same numbers-first drill.