Technical Data

Details: Category: MAC Instruction Book; 06.Mar; Hits: 804

Identification Marks.

Engine number and Prefix letters MAC :	Stamped on left-hand side of crankcase below the cylinder base flange. (Always include serial letters when quoting the identification number.) See Fig. 7.
Frame Number :	Prefix letters RS. Stamped on right-hand side of saddle front mounting lug.
Gearbox Number :	Prefix No. 11/ or 14/. Stamped on right-hand side of housing at top.

Engine.

Capacity (Swept Volume) :	349 cubic centimetres. 21.289 cubic. in.
Bore and stroke :	68 m.m. x 96 m.m. 2.677 x 3.779-in.
Actual Bore diameter :	2.677-in.

Tappet clearance (Cold). For running.	Inlet .005-in.
	Exhaust .005-in.
Tappet clearance (Cold). For setting timing.	Inlet .030-in. to
	Exhaust .035-in.

Note.-Follow instructions on page 26 before checking or resetting tappet clearances.

Ignition Timing.

38 ° before top dead centre, fully advanced (Points open .0015-in.)

Valve Timing. (When checked with .030-in. to .035-in. Tappet clearances.)

Note.-Readjust to running clearances after checking.

	Cam marked	Cam marked	Cam marked
	M17/5	M17/4	M17/7
Inlet opens	30°	50°	19°	Before top dead centre.
Inlet closes	60°	60°	49°	After bottom dead centre.
Exhaust opens	60°	70°	49°	Before bottom dead centre.
Exhaust closes	30°	40°	19°	After top dead centre.

Compression ratio :	6.75 to one.
Compression space :	60-62 c.c.

Valve spring free length :	Outer : 2 9/64 (2.1406) inches.
	Inner : 1 15/16 (1.9375) inches.

Piston Rings.

End gap-Compression rings :	.0085-in. to .0115-in.	Stocked .020-in. .040-in .060-in oversize
End gap. Oil control ring :	.0105 to .0135-in.
Side clearance : Compression rings :	.0005 to .0025-in.
Side clearance. Oil control ring :	.0025 to .0045-in.

Valves. Seat angle 45°

Gudgeon-pin. .624-in. diameter (± .0001-in.) Stocked .001-in. oversize.

Small end bush. .625-in. inside diameter ( +.0005-in. - .0002-in.)

Big end. Crankpin roller track diameter 1.374-in. 16 rollers-caged. 3/16-in. diameter by 9/16-in. long. Stocked .0002-in. and .0004-in. oversize.

Carburetter.

Amal. Type 276EY /1AT. 15/16-in. choke diameter.
	Throttle valve. 6/4.
	Needle jet size 107 (No. 4/061).
	Main jet 130.
	Jet needle position 3.

Monobloc. Type 376/48.
	Throttle valve 3½.
	Needle jet 105.
	Main jet 200.
	Pilot jet 25.
	Needle position 3.

Magneto. Lucas type K1F. Anti-clockwise rotation. Fixed ignition with automatic advance and retard unit type JY16A.

Dynamo. Miller type DVR. 6-volt. Anti-clockwise rotation with automatic voltage regulation.

Lighting Bulbs. Head lamp : 24-W x 24W 6-volt S.B.C. Cap. or 30 X 24W Double Filament Bifocal Pre-focussed type.

Parking : 6-volt, 3w. S.C.C. Cap. or 6-volt, 3W. M.E.S. Cap.

Tail : 6-volt, 6W. S.C.C. Cap.

Stoplight : 6-volt, 18 x 6W. Offset pin Stoplight type.

Battery. 6-volt. 13 A.H. Varley, Exide, or Lucas.

Gearbox. 4-speed. Foot controlled.

Ratios (overall) with 21 tooth final drive sprocket : First, 14 to 1 ; Second, 9.6 to 1 ; Third, 7.3 to 1 ; Fourth (top) 5.5 to 1.

Sprockets. ½-in. pitch x .305-in.

Engine 21 teeth. Clutch, 44 teeth. Final drive, 21 teeth. Rear wheel, 55 teeth.

Chains.

Primary. ½-in. pitch. .305-in. width. .335-in. roller diameter. 67 pitches.

Rear. ½-in. pitch. .305-in. width. .335-in. roller diameter. 124 pitches.

Wheels. Rims : Front, WM2 x 19-in. Rear, WM2 x 19-in.

Spokes :

Front—Brake side. 61-in. x 10 SWG. 18 off.

Front—Left side. 71-in. x 10 SWG. 18 off.

Rear —Brake side. 71-in. X 8 /10 SWG. 20 off.

Rear —Right side. 71-in. x 8 /10 SWG. 20 off.

Tyres. Front, 19-in. X 3.25-in. Rear, 19-in. X 3.25-in.

Tyre Pressures. Minimum solo : Front, 16 lbs. per sq. in. (1.1 atm.) Rear; 18 lbs. per sq. in. (1.2 atm.)

For pressure chart see page 85.

Capacities.

Petrol tank : 3 Imperial gallons. 3.6 U.S. gallons. 13.6 litres.

Oil tank :½ Imperial gallon. .6 U.S. gallon. 2.27 litres.

Gearbox :½ Imperial Pint. .6 U.S. Pint. .28 litres.

Front fork : 1 Imperial Pint. .15 U.S. pint. 71 cu. cent. per strut.

Sparking Plug.

14 m.m. diameter. 18 m.m. (extra long) reach.

Suitable types : KLG FE70. Champion NAB. Lodge HLN.

Dimensions.

Wheel base (In normal loaded position)	53¾-in. - 136.5-cms
Ground clearance (In normal loaded position)	5½-in. - 14-cms.
Saddle height (In normal loaded position)	30½-in. - 77.5-cms.
Overall width	27.1-in. - 70-cms.
Overall length	7 feet - 213-cms.
Weight unladen.	355-lbs. - 161 kgs.

Recommended Lubricants

	B.P.	Duckhams	Mobiloil	Shell	Wakefield
Engine : Summer (Ambient temperatures above 60° Fahrenheit)	Visco-Static* or Energol ' 40 '	Q20/50* or NOL ' Forty '	Mobiloil Special* or Mobiloil B.B.	X100 10W/30* or X100 40	Castrol XXL
Engine : Winter (Ambient temperature below 60° Fahreheit)	Visco-Static* or Energol ' 30 '	Q20/50* or NOL ' Thirty '	Mobiloil Special* or Mobiloil A	X100 10W/30* or X100 30	Castrol XL
Gearbox	Energol ' 40 '	NOL ' Forty '	Mobiloil B.B.	X100 40	Castrol XXL
Front Fork	Energol ' 20 '	NOL ' Twenty '	Mobiloil Arctic	.X100 20/20W	Castrolite
Wheel Hubs	Energrease C3	H.B.B. Grease	Mobil MP	Retinax A or Retinax H	Castrolease ' Heavy '
Primary Chain	Energol 40	NOL ' Forty '	Mobiloil B.B.	X100 40	Castrol XXL
Rear Chain	Energrease C3G	Laminoid	Mobil MP	Retinax A or Retinax H	Castrolease Graphited
For Grease Gun	Energrease C3	H.P.G. Grease	Mobil MP	Retinax A Or Retinax H	Castrolease Medium
For Oil Can	Energol 10	NOL ' Ten '	Mobil Handy Oil	Donax A.1	' Oilit '