BreakstateBreakstate
All vehicles

Classics & other

Norton Commando 750

Roadster1971
Planner link coming soon
Norton Commando 750 Roadster — 1971
Image: Motorcycle Specs

Vitals

Wet weight
191 kg
Seat height
864 mm
Fuel capacity
10 L
Real world range
220 km
Front tyre
4.10 x 19
Rear tyre
4.10 x 19
Tyre pressures
26 / 26 psi solo
TerrainTarmac

Field repair

Fuse box
Under the seat, in-line with the main wiring harness near the battery
Fuses
1
Battery access
Under the seat, in a rubber-mounted battery carrier

Isolastic clearance check and adjustment

  1. 01Place the motorcycle on its center stand and remove the isolastic mount access covers (front and/or rear, per which mount is being checked).
  2. 02Loosen the isolastic mounting nut sufficiently to allow the shim/spacer stack to move.
  3. 03Insert feeler gauges between the shim and the abutment to measure existing clearance.
  4. 04Add or remove thin shim material (some owners historically used beer-can-gauge metal shim stock in a pinch) to achieve the factory clearance target of approximately 0.006-0.010in (0.15-0.25mm).
  5. 05Retighten the mounting nut to factory torque while holding shim position, then recheck clearance.
  6. 06Test-ride and feel for vibration in the 2,500-3,000rpm band; iterate the adjustment if vibration persists.

Primary chaincase cover reseal (O-ring cord method)

  1. 01Drain the primary chaincase oil into a clean container.
  2. 02Remove the primary chaincase outer cover bolts and lift the cover away from the inner case.
  3. 03Clean both mating surfaces thoroughly, removing all traces of old gasket material or sealant.
  4. 04Cut a length of O-ring cord (approximately 5.7mm diameter, slightly oversized versus the factory 5mm spec) to fit the cover's sealing groove, joining the ends with a suitable adhesive.
  5. 05Seat the cord evenly in the groove, then carefully refit the cover, tightening bolts evenly in a criss-cross pattern to avoid distorting the seal.
  6. 06Refill with the correct primary chaincase oil quantity and check for leaks after a short test ride.

Points ignition timing (field method)

  1. 01Remove the points cover on the timing side of the engine.
  2. 02Rotate the engine to bring the piston to the specified 28° BTDC static timing mark (higher-compression Commando spec vs. earlier Atlas models).
  3. 03Connect a test light or continuity buzzer across the points contacts.
  4. 04Loosen the points baseplate retaining screws slightly and rotate the plate until the points just begin to open at the timing mark (light illuminates/buzzer sounds at the moment of opening).
  5. 05Tighten the baseplate screws and recheck the timing mark alignment.
  6. 06As a practical field-tuning check without a timing light: advance the ignition timing slightly and test-ride; if the engine pings/pinks under load, back off ignition timing by one adjustment notch.

Kickstart procedure and starting technique

  1. 01Turn the fuel taps to 'on' and use the choke/air lever if starting cold.
  2. 02Tickle the Amal concentric carburetors briefly to richen the mixture for a cold start (press down on the float tickler button until fuel just begins to show at the overflow).
  3. 03Find top dead center by slowly rotating the kickstart lever until compression resistance is felt, then ease back slightly past this point.
  4. 04Deliver a firm, full-stroke kick through the compression stroke.
  5. 05Once running, ease the choke off gradually as the engine warms.

Data sheet

Dimensions & weights

Wet weight
191 kg
Seat height
864 mm
Wheelbase
1441 mm

Engine & drivetrain

Engine
745 cc · Parallel twin
Cooling
Air cooled
Output
58 hp · 54 Nm
Transmission
4-speed
Final drive
Chain
Fuelling
Electronic fuel injection

Fuel & range

Fuel capacity
10 L
Real world range
220 km

Electronics & rider aids

Ride modes
None
Cruise control
No
Traction control
No
ABS
Yes
Heated grips
No
Heated seat
No

Service intervals

Service interval
3,000 km
Chain lube
every 500 km

Protection

Bash plate
None
Radiator guard
No
Oil cooler guard
No
Hand guards
No

Consumables & service specs

Every value carries its source.

Tyres

Front
4.10 x 19Per factory service manual. Note: a secondary aggregator source lists 3.25-19 for 1970-71 models, conflicting with the factory manual; factory manual figure used per source-discipline priority.Norton Commando Factory Service Manual
Rear
4.10 x 19Per factory service manual. Note: a secondary aggregator source lists 4.00-18 for 1970-71 models, conflicting with the factory manual; factory manual figure used per source-discipline priority.Norton Commando Factory Service Manual

Tyre pressures

Front — solo
26 psiSolo rider, cold tyreNorton Commando Factory Service Manual
Rear — solo
26 psiSolo rider, cold tyreNorton Commando Factory Service Manual

Engine oil

Viscosity
SAE 40 (summer) / SAE 20W-50 (modern equivalent, multigrade)Norton Owners Club recommends modern SAE 20W-50 monograde-equivalent multigrade motor oil as the practical substitute for period-correct straight-40 non-detergent oil, especially where no external oil filter is fittedNorton Owners Club — Oil/Tyre Pressure
Capacity
2.8 l5 Imperial pints / 6 US pints, held in the frame-mounted oil tank (dry-sump system)Norton Commando Factory Service Manual

Brakes

Fluid type
Lockheed Series 329 (period spec); DOT 4 commonly substituted by owners todaySeries 329 was the period Lockheed brake fluid spec for Commando hydraulic front disc brakes; Norton Owners Club forum members commonly report substituting modern DOT 4Norton Owners Club — Oil/Tyre Pressure

Forks

Oil viscosity
SAE 20WNorton Owners Club — Oil/Tyre Pressure
Oil capacity
150 mlPer fork legNorton Commando Factory Service Manual

Final drive

Chain
Primary: 92-pitch triplex, 0.375 x 0.250in; Secondary (rear drive): 99-pitch simplex, 0.400 x 0.380inEnclosed primary chaincase (oil bath); rear chain is open, non-O-ring vintage typeNorton Commando Factory Service Manual

Spark plugs

Type
Champion N7YNorton Commando Factory Service Manual
Gap
0.59-0.72 mm0.023-0.028inNorton Commando Factory Service Manual
Quantity
2Parallel-twin engine, one plug per cylinderNorton Commando Factory Service Manual

Battery

Type
Norton Villiers / Lucas 12N9-4B, 12V 10AhPositive earth electrical systemNorton Commando Factory Service Manual

Fuel

Minimum octane
97 RON (period leaded premium); modern equivalent 91-93 AKI premium unleaded plus a lead-substitute additive recommended due to non-hardened valve seatsNorton Owners Club — Oil/Tyre Pressure

What breaks first and where.

01

Isolastic engine mount vibration / mis-set clearance

ModerateWidespread

The Commando's signature Isolastic rubber engine-mounting system, designed to isolate vibration from the rider, requires periodic clearance checks and adjustment. If the isolastic rubber shims are mis-set (clearance should be approximately 0.006-0.010in / 0.15-0.25mm, checked with feeler gauges), or if replacement rubbers of incorrect hardness are fitted, the bike develops pronounced vibration, particularly in a resonance band around 2,500-3,000 rpm. This is a timeless, well-documented Commando platform characteristic rather than a specific manufacturing defect.

Symptoms

  • Pronounced vibration through footpegs/handlebars/seat in the 2,500-3,000rpm range
  • Vibration that clears above approximately 3,000rpm
  • Increased vibration after fitting replacement isolastic rubbers of the wrong hardness (e.g., later MK3 rubbers on an earlier Commando)

Field repairableYes — Loosen the isolastic mounting nut, use a bar and feeler gauge to reset clearance to factory spec, retighten, then test-ride and iterate; soft-compound reproduction rubbers (e.g., from ANIL) are available for owners seeking a period-correct feel.

Norton Owners Club — Isolastic Mounts Forum
02

Primary chaincase oil leaks

MinorCommon

The primary chaincase cover on Commandos is a well-known chronic oil-leak point, most commonly at the cover-to-case joint sealing surface. Owners have documented persistent seepage even after gasket replacement, often traced to the factory O-ring cord seal being undersized or the cover not seating flat.

Symptoms

  • Oil seepage/pooling below the primary chaincase cover
  • Gradual loss of primary chaincase oil level requiring frequent top-ups

Field repairableYes — Reseal using a slightly oversized O-ring cord (approx. 5.7mm vs OEM approx. 5mm) in place of the stock gasket/seal, ensuring the cover mounting surface is flat and clean before reassembly.

AccessNorton — Chaincase Leaks
03

Oil pressure loss / relief valve and pump wear

SeriousOccasional

Norton Owners Club technical documentation and owner reports describe several oil-pressure-related failure modes on Commando engines: sticking pressure relief valves, oil pump drive gear wear (particularly on Atlas-carryover-style pumps vs. later worm-gear pumps), incorrectly oriented rocker spindles passing excess oil, and — in at least one documented case — a crankshaft oil seal failure in the timing cover causing a sudden and complete loss of oil pressure while riding.

Symptoms

  • Low or erratic oil pressure gauge readings (normal range approximately 20-60psi depending on temperature/rpm/model)
  • Sudden drop to zero oil pressure while riding (severe case)
  • Excessive oil consumption or externally visible leaks at the timing cover

Field repairableYes — Relief valve can be inspected/cleaned/reseated in the field; oil pump and timing-cover seal replacement require more extensive disassembly but are documented DIY procedures within the Commando community.

Norton Owners Club — Oil Pressure