Identification Markings.
(To be quoted when ordering spares or requesting Service information) Engine Number *(prefix MSS). Stamped on crankcase at left-hand side below cylinder base. Frame Number *(prefix RS). Stamped on right-hand side of seat front mounting lug. Gearbox Number *(Prefix 12— or 14—). Stamped on top of gearbox housing on right-hand side.
* The prefix letters or numbers identify, the type and must always be quoted. The serial number alone is insufficient.
Engine Dimensions.
Cylinder capacity (swept volume) :
499 cubic cms.
30.45 cubic ins.
Cylinder bore :
86 m.m.
3.385-ins.
Stroke :
86 m.m.
3.385-ins.
Tappet Clearances.§ (Set cold).
Running clearance .. ..
Inlet .005-ins.
Exhaust .005-ins.
For checking timing ..
Inlet .030-ins.
Exhaust .030-ins.
§ See page 25 before checking
or adjusting.
Valve Timing. Cam No. M17 /7. When checked with .030-in. tappet clearance :
Inlet opens . .
.. ..
19- before top dead centre.
Inlet closes ..
• . .. ..
49° after bottom dead centre.
Exhaust opens
.. ..
49° before bottom dead centre.
Exhaust closes
.. .. ..
19° after top dead centre.
Compression Ratio. 6.8 to one.
Sparking Plug. 14 m.m. dia. 18 m.m. (extra long) reach.
Suitable types : Champion NA8 ; KLG FE80 ; Lodge HLN.
Piston Rings.
End gap. Compression rings .. ..
.010-ins. to .015-ins.
End gap. Scraper ring .. . . ..
.010-ins. to .015-ins.
Side clearance : Compression rings .
.001-ins. to .003-ins.
Side clearance : Scraper ring . . ..
.0027-ins. to .0047-ins.
Valves.
Seat angle 45°
Gudgeon Pin.
.8235-ins. diameter. (± .0001-ins.)
Small end Bush.
.8245-ins. diameter. ( +.0005-ins.)
(—.0002-ins.)
Big End.
Crankpin roller track diameter, 1.499-ins.
Crankpin rollers, *-ins. x 9/16-ins. 18 off, caged,
single row.
Rollers stocked .0002-ins. and .0004-ins. oversize.
Carburetter.
Make and Type : choke bore.
Amal Type 276BS /1AT. 8° downdraught. 1 *-ins.
Setting : Main jet jet size standard
150, Throttle valve 6 /4. Jet needle 6 /065, Needle Needle set with clip in third groove from top.
Magneto.
Lucas type K1F. Fixed ignition, anti-clockwise
rotation. Fitted with Lucas type JY16A Auto- matic timing unit.
6
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.
Lighting Bulbs. Headlamp main bulb. 6-volt, 30 x 24W. Bifocal prefocussed.
Headlamp parking bulb. 6-volt, 3W. M.E.S. Cap. Rear and stop lamp bulb. 6-volt, 18 X 6W. (Offset pin). Speedometer bulb. 6-volt, 18W. M.B.C. Cap.
Battery. 6-v. 13 ampere hour. Varley, Lucas, or Exide.
Gearbox. Four speed, constant mesh, foot controlled. Oil
lubricated.
Gear Ratios.
Gearboxes, Prefix No. 12 :
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. 14 :
With solo sprocket (18T) : First, 11.24 ; Second, 7.78 ; Third, 5.91; Fourth, 4.9 to one.
With s /car sprocket (16T) : First, 12.61 ; Second, 8.73 ; Third, 6.64 ; Fourth, 5.5 to one.
Chains and Sprockets.
Primary Chain : .5-ins. pitch; .305-ins. wide; .335-ins. roller dia.; 68 pitches.
Rear Chain : .625-ins. pitch; .380-ins. wide; .4-ins. roller dia.;
$101 pitches.
± .100 Pitches when 16T driving sprocket is fitted.
Sprockets. Engine. 23T. Clutch, 44T.
Gearbox (Solo) 18T. Gearbox (S /car) 16T.
Rear Wheel, 46T.
Wheels and Tyres.
Rims : WM2 x 19-ins. front. WM2 x 19-ins. rear.
Tyres. 19-ins. x 3.25-ins. front. 19-ins. x 3.25-ins. rear.
Tyre Pressures-Minimum. Solo : Front, 16-lbs. per sq. in. ; Rear,
18-lbs. per sq. in.
See page 82 for load and pressure table.
Fuel and Oil Capacities.
Fuel Tank : 3 imperial gallons. 13.6 litres. 3.6 U.S. gallons.
Oil Tank : .5 imperial gallons. 2.27 litres. .6 U.S. gallons.
Gearbox : .5 imperial pint. 28 litres. .6 U.S. Pint. Front Fork : (per strut) .125 imperial pint. 71 cubic cm. .15 U.S. Pint.
Principle Dimensions.
Wheel base : (in normal loaded position) 53.75-ins. 136.5 cms.
Ground clearance : ( „ „ „ ) 5.5-ins. 14 cms.
Seat height : ( „ „ ) 30.5-ins. 77.5 cms.
Overall Width. 27.5-ins. 70 cms.
Overall Length. 7-feet. 213 cms.
Unladen Weight. 375-lbs. 170 kilograms.