Norton Commando Workshop Manual

## Technical Data

# A

| Cylinder block
|  | Material: Cast iron
|  | Finished size: | Grade A 2.8746/2.8750
|  |  |  | Grade B 2.8750/2.8754
| Cylinder head | Standard | Combat
|  | Material: | RR 53 B | RR 53 B
|  | Valve seat angle: | 45° | 45°
|  | Inlet port nominal dia.: | 1 1/8 in. (28.573 mm) | 1 1/8 in. - 1 1/4 in. (28.575 - 31.75 mm)
|  | Ex. port nominal dia.: | 1 1/4 in. (31.76 mm) | 1 1/4 in. (31.75 mm)
|  | Ex. ring thread size: | 1.997 in. x 14 T.P.I. | 1.997 in. x 14 T.P.I.
| Camshaft | Standard | Combat
|  | Material: | EN 32 B | EN 32 5
|  | Max lift- | Inlet | 0.332 in. (8.389 mm) | .390 in. (9.906 mm)
|  |  | exhaust: | 0.322 in. (8.389 mm) | .346 in. (8.788 mm)
|  | Base circle dia.: | .885 in. (22.479 mm) | .906 in. (23.012 mm)
|  | Bearing journal dia.: | .8735 in. (22.187 mm) | .8735 in. (22.187 mm)
| Camshaft bushes | Pre 1972 | 1972 Onward
|  | Fitted l.D. (Left bush): | .8750 in. (22.225 mm) | .8750 in. (22.225 mm)
|  | Fitted l.D. (Right bush): | .8750 in. (22.225 mm) | .8750 in. (22.225 mm)
| Tappets
|  | Material: Cast iron Grade 1 4 - stellite tipped
| Push rods
|  | Material: Heat treated Dural tube "B" or "S" Inlet - assembled length: 8.166/8.130 in. (207.41 6/206.466 mm) Exhaust-assembled length: 7.321/7.285 in. (186.053/185.039 mm)
| Rockers
|  | Material: EN33 Rocker ratio - inlet: 1.13 :1 Rocker ratio - exhaust: 1.13:1 Bore diameter: 0.4998/0.5003 in. (12.694/12.708 mm) Adjuster thread size: 9/32 in. x 26 TPI. Whit Form
| Rocker shaft
|  | Diameter: .4988/.4985 in. (12.694/12.669 mm)
| Valve (tappet) Clearances (engine cold)
|  | Inlet: 006 in. (0.15 mm) (Commando); .008 in. (0.2 mm) (Combat) Exhaust: .008 in. (0,2 mm) (Commando); .010 in. (0.25 mm) (Combat)
| Valve Lift | Standard | Combat
|  |  |  | Inlet: .375 in. (9.525 mm) | Inlet: .441 in. (11.21 mm)
|  |  |  | Exhaust: .375 in. (9.525 mm) | Exhaust: .391 in. (9.931 mm)
| Valve duration: | Standard | Combat
|  | (excluding ramps) | 152° | 164°

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