MAC Instruction Book

Publication F.469/4R/400, January 1965

Issued as a guide to the complete servicing and repair of spring-framed MAC models. Intended primarily for Agents and Repairers.

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 '

Note: page numbers referred to are from the original manual.

Fig	1	Front hub - Sectional View	9
Fig	2	The steering head	11
Fig	3	The Velocette telescopic fork	13
Fig	4	Draw bolt for fitting head bearing cups	14
Fig	5	Oil tank, ball valve, and filter	17
Fig	6	Crankcase suction filter	20
Fig	7	Dynamo belt adjustment, etc	21
Fig	8	Positions of rocker cover bolts	23
Fig	9	Cylinder head and rocker assembly	23
Fig	10	Setting of valve guides	25
Fig	11	Diagram of clutch operating mechanism	27
Fig	11a	Diagram of clutch operating mechanism	27
Fig	12	Adjustment of clutch	28
Fig	13	Sleeve gear nut and peg spanner	32
Fig	14	Sleeve gear nut adapter X2959	34
Fig	15	Kickstart ratchet and springs	35
Fig	16	The gearbox end cover, etc	36
Fig	17	Lucas automatic timing unit	38
Fig	18	Removal of oil-pump and crankshaft pinion	39
Fig	19	Pump alignment tool X2719	40
Fig	20	Crankshaft pinion extractor X2721	41
Fig	21	Positions of timing marks	46
Fig	22	Ballrace retaining ring tool X2725	51
Fig	23	Positions of selector forks	52
Fig	24	Rear hub assembly Sectional view	34
Fig	25	Rear suspension adjustment	55
Fig	26	Assembly tool X2992	57
Fig	27	Torque tube clamp tool X2938	58
Fig	28	The Amal carburetter (Section)	60
Fig	29	Section of pilot passages	60
Fig	30	The Carburetter	63
Fig	31	Phases of throttle openings	64
Fig	32	Fuel tap and strainer	66
Fig	33	KLG sparking plug	67
Fig	34	Miller dynamo Commutator end	69
Fig	35	Miller dynamo Exploded view	71
Fig	36	Miller bearing lock ring spanner	72
Fig	37	Miller cut-out	75
Fig	38	Wiring diagram (Miller lighting set)	76
Fig	39	Theoretical diagram (Miller dynamo and Regulator)	77
Fig	40	Lucas type KIF magneto	80
Fig	41	Rear brake and rear chain adjustment	83
Fig	42	Pannier frame and bags	86


Air cleaner. Maintenance of	65	Crankcase. Separating	42
Ammeter. Testing	76	Crankcase. Main bearings	42
Automatic timing unit. Removal of	38	Crankcase suction filter	20
Automatic timing unit. (Illustration)	38	Crankcase suction filter. (Illustration)	20
Automatic voltage regulator	74	Crankshaft timing-pinion. Removal of	41
		Crankshaft-pinion extractor. (Illustration)	41
Ball valve assembly	19	Cut-out. Adjustment of	75
Ball valve assembly. (Illustration)	17	Cut-out. (Illustration)	75
Ballrace retaining ring tool. (Illustration)	51	Cylinder. Removal of	37
Battery. Filling and charging	78	Cylinder. Refitting	45
Battery. Maintenance and storage of	78	Cylinder bore diameter	6
Big-end bearing. Overhauling	43	Cylinder head. Removal of	22
Big-end rollers. Oversizes of	44	Cylinder head. Refitting	25
Brake assembly. Front	10
Brake assembly. Rear	53	Decarbonising and grinding in valves	22
Brake adjustment. Rear. (Illustration)	83	Dynamo belt adjustment	74
Brakes. Relining	53	Dynamo belt adjustment. (Illustration)	21
		Dynamo belt cover. Removal of	31
Carburetter. (Illustration)	63	Dynamo. Dismantling and reassembling	70
Carburetter. Sectional view	60	Dynamo. Exploded view	71
Carburetter, Description of	61	Dynamo. Removal of	31
Carburetter. Dismantling, etc.	61	Dynamo. Testing	73
Carburetter. Setting and adjusting	64	Dynamo. Special spanner	72
Chain adjustment. (Primary)	82
Chain adjustment. (Primary) (Illustration)	36	Engine bearings	42
Chain adjustment. (Rear)	83	Engine lubrication system	17
Chain adjustment. (Rear) (Illustration)	83	Engine. Overhauling	37
Cleaning the machine	85	Engine. Removal from frame	36
Clutch. Description of working	26	Engine shaft shock absorber	22
Clutch. Diagram of operating mechanism	27
Clutch. Dismantling	48	Fabric oil filter	20
Clutch. Reassembling	48	Fabric oil filter. (Illustration)	17
Clutch. Adjustment of	28	Flywheel assembly. Lining up	44
Clutch adjustment. (Illustration)	28	Flywheel assembly. Overhauling	43
Clutch thrust bearing	49	Flywheel assembly. Refitting	42
Commutator Cleaning	72	Fork. Description of working	12
Commutator Connections. (Illustration)	69	Fork. Dismantling	15
		Fork. Maintenance of	15
		Fork. Reassembling	16
		Fork. (Sectional illustration)	13

Gearbox bearings	50	Oil circulation system
Gearbox. Dismantling	49	Oil filter (Suction)	20
Gearbox end cover. (Illustration)	36	Oil filter (Suction). (Illustration)	20
Gearbox. Reassembling	51	Oil filter (Fabric)	20
Gearbox. Removal from frame	36	Oil filter (Fabric). (Illustration)	17
Gearbox. Separating from engine	37	Oil-pump. Priming	18
Gear operating mechanism	50	Oil-pump. Overhaul	40
		Oil-pump. Removal	39
Hub (Front). (Sectional illustration)	9	Oil-pump. Removal. (Illustration)	39
Hub. (Rear). (Sectional illustration)	54	Oil-pump alignment tool. (Illustration)	40
Hub bearings. (Front). Dismantling	10	Oil. Recommended grades	8
Hub bearings. (Rear). Dismantling	54	Overhead rockers. Removal	23
		Overhead rockers. (Illustration)	23
Intermediate timing gear adjustment	47	Overhead rockers. Refitting	25
Intermediate timing gear. (Illustration)	46
Index to Illustrations	5	Panniers. Fitting Instructions	87
		Phases of throttle opening. (Illustration)	64
Kickstart mechanism. (Illustration)	35	Petrol tap and strainer. (Illustration)	66
Kickstart mechanism. Dismantling	34	Piston. Removal	36
Kickstart mechanism. Reassembling	35	Piston. Refitting	45
Kickstart return spring. Replacing	35	Piston ring gaps	37
		Primary chain. Removal	32
Lamps	68	Primary chain. Refitting	33
Lamp bulbs	68	Primary chain adjustment. (Illustration)	35
Lighting set	68	Primary chain case. Removal	31
Lighting wiring diagram	76	Primary chain case. Refitting	33
Lubrication of chains	82
Lubrication of engine	17	Rear suspension. Adjustment	55
Lubrication of fork	15	Rear suspension adjustment: (Illustration)	55
Lubrication of gearbox	8	Rear suspension. Maintenance	56
Lubrication of magneto	79	Rear suspension units	56
Lubrication of wheel bearings	10, 54	Retiming Ignition	47
		Rocker cover. Removal	22
Main bearings. Removal	42	Rocker cover. Refitting	26
Main bearings. Refitting	42	Rocker cover bolts. Location (Illustration)	23
Magneto. Maintenance	79
Magneto. Removal	81	Shock absorber. Removal	22
Magneto. Refitting	82	Sleeve gear nut. Refitting	33
Magneto. Testing	81	Sleeve gear nut adaptor. (Illustration)	34
Magneto. Timing	47	Sleeve gear nut and spanner. (Illustration)	32
Magneto. (Illustration)	79	Sparking plugs. Recommended types	67

Sparking plug. Maintenance	68	Transfers. Instructions for fixing	84
Sparking plug. (Illustration)	67	Trunnion shaft. Removal	58
Speedometer drive	52	Trunnion shaft. Refitting	59
Steering head bearing. Adjustment	11	Tyres. Maintenance	85
Steering head. (Illustration)	11	Tyre pressures	85
Steering head bearing tool. (Illustration)	14
		Valves. Refacing and grinding in	24
Tappet adjustment. (Illustration)	23	Valves. Removal. (Illustration)	23
Tappet clearances	26	Valve guide. Renewal	24
Technical data	6	Valve guide location. (Illustration)	25
Theoretical wiring diagram	77	Voltage regulator. Testing and adjusting	74
Timing gear	46
Timing gear markings. (Illustration)	46	Wheel bearings (Front). Removal	10
Timing-pinion. Removal	41	Wheel bearing (Rear). Removal	54
Timing cover. Removal	38	Wheel bearings	10, 54
Torque arms. Removal	57
Torque arms. Realignment	59
Torque arm clamp tool. (Illustration)	58

This Service Manual is issued as a guide to the complete servicing and repair of the MAC spring frame model Velocette and is intended primarily for the use of Agents and Repairers.
We have intentionally omitted some of the various routine maintenance jobs and adjustments already covered by the Owners' Handbook for the same model as these are usually undertaken by the rider.

References are made in places to special Service Tools which are essential for certain operations. It is earnestly hoped that Agents and Repairers will equip their workshops with them. They save so much labour and avoid the risk of damaging components that their acquisition is well justified.

It is possible that some private owners who are in the habit of doing most of their own repairs will obtain copies of this book. To any of these we suggest that in their own interest they entrust any repairs, which are likely to prove beyond their capacity, to their local Agent and not "bite off more than they can chew."

Publication No.F.469/4R/400. VELOCE LIMITED.

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