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Identification Markings.

(To be quoted when ordering spares or requesting Service information)

Engine Number *(Prefix VR, VM or MSS). Stamped on crankcase at left-hand side below cylinder base. (Scramblers have suffix 'S'.)

Frame Number *(Prefix RS). Stamped on right-hand side of seat front mounting lug. (Scramblers have suffix 'S' or /35.)

Gearbox Number *(Prefix 12– or 14–). Stamped on top of gearbox housing on right-hand side. (T.T. close ratio boxes have suffix 'R'.)

* The prefix letters or numbers identify the type and must always be quoted. The serial number alone is insufficient

Engine Dimensions.

Tappet Clearances.† (Set cold).

†See page 25 before checking or adjusting.

*For Scrambler clearances see page 96. Thruxton model see supplement

Valve Timing. When checked with tappet clearances of .053° inlet, and .052° exhaust.

Cam M17 /8, Venom and Viper from En. No. VR1262 and Scrambler

Cam M17 /7, MSS and Viper to En. No. VR1261-

Compression Ratios.

MSS 6.8 to one (86 to 88 c.c.). Venom 8 to one (68 to 69 c.c.). Viper 8.5 to one (47 to 48 c.c.). 350 Scrambler and Viper Clubman 9.3 to 1 (42 c.c.). 500 Scrambler and Venom Clubman 8.75 to 1 (64-65 c.c.).

Sparking Plug.          14 m.m. dia. 18 m.m. (extra long) reach.

Suitable types for MSS : Champion NA8; KLG FE80; Lodge HLN.

For Venom and Viper : Champion NA10 : NAS FEIN : Lodge 3HLN. See also page 71.

Piston Rings.

Valves.                       Seat angle 45°

Carburetters. Monobloc or Concentric type 8° downdraught. Early Clubman and Scrambler models were fitted with the Amal 10TT9 type

 Earlier Venom models were fitted with the Concentric type carburetter Type R930/15, which had the following settings : Main Jet 270 Needle Jet 107 Pilot Jet 30 Throttle Valve 4 Needle Set in bottom groove position.

Ignition Timing. Fully advanced before top dead centre :

Magneto

Lucas type K1F. Fixed ignition, anti-clockwise rotation. Fitted with Lucas type JY16A Automatic timing unit.

B.T.H. Type BKH1 (Hand controller on Clubman and Scrambler models).

Coil Ignition. Lucas type.

Lighting Equipment.

Dynamo. Miller. Type DVR 6-volt. Belt driven anti-clockwise rotation with Automatic Voltage regulator unit.

Head Lamp. Miller Type 79CV, incorporating switch and ammeter. 

(1955 to Mid 1956).

Miller Type 180CV on Viper, Venom and MSS.

Lucas type SS700P.

Lighting

Bulbs.

Headlamp main bulb. 6-volt, 30 x 24W. Bifocal prefocussed.

Headlamp parking bulb. 6-volt, 3W. M.E.S. Cap. Rear lamp. 6-volt, 6W. S.C.C. Cap on MSS. Rear and stop lamp bulb. 6-volt, 18 x 6W. (Offset pin.), Viper and Venom.

Speedometer bulb. 6-volt, .18W. M.B.C. Cap.

Battery. 6-volt 13 ampere hour. Varley, Lucas, or Exide

Gearbox. Four speed, constant mesh, foot controlled. Oil lubricated.

Gear Ratios.

Gearboxes, Prefix No. 14 : (MSS.)

With solo sprocket (18T) : First, 12.4 ; Second, 8.57 ; Third, 6.52 ; Fourth, 4.9 to one.

With s /car sprocket (16T) : First, 13.91; Second, 9.625 ; Third, 7.32 ; Fourth, 5.5 to one.

Gearboxes Prefix No. 12. (Viper and Venom.)

Venom. With solo sprocket (18T) : First, 11.24 ; Second, 7.78 ; Third, 5.91; Fourth, 4.9 to one.

Venom. With s /car sprocket (16T) : First, 12.62 ; Second, 8.73 ; Third, 6.64 ; Fourth, 5.5 to one.

Viper. With solo sprocket (21T) : First, 12.62 ; Second, 8.73 ;  Third, 6.64; Fourth, 5.5 to one.

Gearboxes Prefix 12 : Suffix R. (Clubman models).

Venom. With solo sprocket (18T) : First, 9.25 ; Second, 7.03 ; Third, 5.35 ; Top, 4.9.

Viper. With solo sprocket (21) : First, 10.45 ; Second, 7.94 ; Third, 6.03 ; Top, 5.5.

Chains and Sprockets.

Primary Chain. : .5-in. pitch ; .305-in. wide ; .335-in. roller dia. ; MSS and Venom 68 pitches ; Viper 67 pitches.

Rear Chain :      MSS and Venom : .625-in. pitch ; .380-in. wide ; .4-in. roller dia. ; 101 pitches. 100 pitches when 16T driving sprocket is fitted.

Viper.  .5-in. pitch ; .305-in. wide ; 124 pitches.

Sprockets.

MSS and Venom : Engine. 23T. Clutch, 44T. Gearbox (Solo) 18T. Gearbox (S /car) 16T. Rear Wheel, 46 T.

Viper. Engine. 21T. Clutch, 44T. Gearbox. 21T. Rear wheel, 55T.

Wheels and Tyres.

Rims : WM2 x 19-in. front. WM2 x 19-in. rear.