AJS G2 Building instructions

SERVICEANDOVERHAULMANUAL
FORTHE
AJS& MATCHLESS
SINGLEMOTORCYCLES
F.NEILL
by
Covering1958to1964Lightweight250c.c.and350c.c.
modelsG2G2SG2CSG2CSR1414S14CS14CSR
G58 and1957to1966Heavyweight350c.c.,500c.c.
and600c.c.modelsG3G3CG3SG3LSG3LCSG80
G80SG80CSTCS1616S16C16CS16MS16MC
16MCS1818S18CS
F.
NEILL
AJS &
MATCHLESS SINGLES 1957-1966 Lodgemark Press
Reprinted in Belgium
LODGEMARK PRESS LTD
BANK HOUSE, SUMMERHILL, CHISLEHURST,
KENT BR7 5RD, ENGLAND
TWO-STROKE HIGH
PERFORMANCE ENGINE
DESIGN & TUNING
By World famous engine designer
Bossaglia who was responsible for
most of the Italian rotary valve kart
engines including Komets and Parillas
from the very first—the V11 to the K89.
227 pages packed with information
including : Characteristics and types of
two-stroke motors. Multi-cylinder
engines, Fuel, Quantity of air necessary
for combustion. Determining the power,
The Pressure Volume diagram,
Performance, The operation of the
crank, Balance, The Stroke/bore ratio,
Third port induction, Induction through
valves, Blade type valves, Cylindrical
rotary valves, Rotating disc valves,
Transfer and scavenging with transverse
flow, tangential flow, uni-directional
flow, Counter-flow scavenging,
Position of the ports,
Bi-metal cylinders, Cylinders with
chromed bore, The piston, The gudgeon
pin, The piston rings, Constructional
ideas for the piston, The head, The
crankcase, The crankshaft, Modification
of the crank shaft assembly, Modification
of cylinder, piston and head, The
carburettor, Fuel pumps, Carburation
adjustments, Fuel injection, The magneto
The sparking plug, Ignition timing,
Electronic ignition, Lubrication,
Exhaust System, Mufflers, Exhaust
system for multi-cylinder engines,
Exhaust silencers, Test procedure,
Examples of modifications.
£4.35 (incl. insurance) Ref 290
TWO STROKES & TUNING
TWO-STROKE EXHAUST
SYSTEMS
Full details on how to calculate design
and make competition exhaust systems.
55p Ref 252 Available again March
TWO-STROKE PORTS FOR
POWER
Read how to calculate and design the
right port timing for your requirements.
55p Ref 253.
TWO-STROKE CARBURATION
AND IGNITION
Roy Bacon's third book on racing two
strokes. Vital information on carburation
& ignition.
55p Ref 281
ROTARY VALVE TWO-STROKE
KART ENGINES
All about 100cc kart engines. Includes
Arisco, B.M., Corsair, Famrel, Komet,
Parilla, Petry, Saetta, Starr, Basic
preparation, using Bleepers,
Transistorised Ignition, Tillotson carbs.
£1.10 Ref 288
IMPROVING TWO STROKE
ENGINE PERFORMANCE
Villiers, Maico, Vespa, Marcelle,
Zundapp, Itom, DKW, Lambretta.
85p Ref 135
BUILDING KARTS
KARTING FOR SCHOOLS&
YOUTH GROUPS
Organising, driving and building
low-cost karts. Forming clubs.
90p Ref 292
JAVELIN SET No. 1
Details and drawings to build a low
price kart without a tube bender.
Suitable for 2 or 4-stroke engines
without gearbox, max 5 hp & 40 lbs for
Cadet racing, fun and driver training.
Bolted-construction.
50p Ref 270
CADET SET No. 3
Details anddrawings to make afun kart
without a tube bender. Suitable for 2 or
4 stroke engines without a gearbox up to
5 hp and weighing up to 40 lbs. New
edition provides option ofbolted or
welded construction.
Any parts can be purchased ifrequired.
£1.10 Ref 293
ABOUT KART RACING
STARTING KARTING
How to start the sport explained, details
of classes, location of tracks. British
clubs and addresses. Where to buy
karts, engines fr accessories. 4th Edn.
50p Ref 286
GOING KARTING
Covers every aspect of karting, how to
buy your kart and engine, racing on
motor tracks, etc. 4th Edn.
£1.45 Ref 266
R.A.C. KART REGS 1974
All the rules and regulations governing
drivers, organisers, tracks, karts and
engines. British calendar of events,
club addresses and list of tracks.
50p Ref 130
www.ajs-matchless.info

www.ajs-matchless.info

www.ajs-matchless.info

Technicaldetails,togetherwithworkinginstructionsgiveninensuing
chaptersaresolelyconfinedtothesinglecylinderA.J.S.andMatchless
models,whicharesimilarregardingdesign,andidentifiedbythepetrol
tankemblemsandcolourfinish.Theenginedesignoftheheavyweight
singlecylindermodelsisbasicallyidenticalsince1948,andinconsequence
theengineassemblyinstructions—inthemain—applytoallmodelsmade
from1948to1966.Thelightweightmodelswereintroducedin1959and
designchangeswithminormodificationsaredescribedtoenableowners
toincorporatethelaterpartsintoearlierengines,ifsodesired.
Asthecrankcasesforthe350and500heavyweightenginesareidentical
—since1948—thesmallcapacityenginecanbeconvertedtothelarger
typebysubstitutingpartsinthetopportionoftheengine.
The author and the publishers wish to express their thanks to Norton
Villiers Ltd. for their co-operation in the preparation of this book and
permission to publish the text and illustrations.
www.ajs-matchless.info

SERVICEANDOVERHAULMANUAL
FORTHE
AJS& MATCHLESS
SINGLEMOTORCYCLES
by
F.NEILL
S.B.N.850770203
©LODGEMARKPRESSLIMITED
BankHouse,SusanWood,Chislehurst
KentBR75RD,England
EDITORH.A.NIMMO
www.ajs-matchless.info

Technical data
Engine design changes
Lubrication
Recommended lubricants
Periodical maintenance
Engine servicing
Engine overhaul
Gearbox and Clutch
Front forks
Rear suspension units
Frame
Wheel bearings
Wheels and Brakes
Transmission
Carburettor
Wipac alternator
Wipac electrical service
Lucas electrical service
Lucas coil ignition
Magneto
Dynamo
Wiring diagrams
5
13
18
20
21
23
35
54
71
84
85
87
90
100
102
104
107
111
112
113
114
120
Contents
page
…… … …
… … …
…… … … …
… … …
… … …
…… … …
…… … …
… … …
…… … … …
…… … … …
…… … … …
…… … … …
…… … … …
…… … … …
… … …
…… … …
…… … …
…… … …
…… … …
… … …
… … …
… … …
www.ajs-matchless.info

Identity
Engine Number
Frame Number
Cylinder Bore
Stroke
Cubic Capacity
Carburettor
Type 376/99
Main jet (without air filter)
Main jet (with air filter)
Choke size
Throttle slide
Needle position
Capacities
Petrol tank
Oil capacity
Gear box
Front chain case
Compression Ratio
General
Seat height
Wheelbase
Weight
Ground clearance
Cylinder bore
Nominal size
Piston Size
Skirt diameter (taken at right angle
to gudgeon pin top of the skirt).
High limit
Low limit
On the crankcase near engine
plate cowling.
On right hand side of frame head
lug.
69,85 mm.
64.84 mm.
248.5 c.c. (15.2 cu. ins.)
Amal Monobloc (12° inclination)
180
180
1z"
3½
central (.106) pilot 25
3¼ gallons (12.5 litres)
2½ pints (1.4 litres)
3 pints (1.8 litres)
568 c.c.
7.8 to 1
30" (76 cms.)
53" (134.5 cms.)
325 lbs. (148 kilos)
5½" (14 cms.)
2.7500 + .0005"
– .0005"
2.7488"
2.7480"
250 c.c. CSR 1962/64 Models
Compression Ratio
Valve springs (Scrambler Type)
Inlet Valve head diameter (New Type)
Gear Ratios
Top
Third
Second
First
8 to 1
Spring free length 1½" between
wire centres.
1S"
6.39 to 1
8.31 to 1
11.82 to 1
18.68 to 1
250 c.c. G2 and G2S Models
TECHNICAL DATA
5
www.ajs-matchless.info

Sprocket Sizes
Engine
Gear box
Clutch
Rear Wheel
Chain Sizes
Front
Rear
Carburettor
Main jet
Pilot jet
Throttle slide
Needle jet
Needle location
Spark Plug
22 teeth
18 teeth
46 teeth
55 teeth
Duplex .315 x .638" (72 links)
½" x .305" (124 links)
Type 389/82 (18" bore)
Size 200
Size 30
3
Size .106"
Central notch
FE 80
250 c.c. CSR 1965/66 Models
Compression Ratio
Ignition Timing
Valve spring (coil type)
Gear Ratios
Internal Ratios
Top
Third
Second
First
Actual Ratios
Top
Third
Second
First
Spark Plug
Piston Rings
Compression rings
Diameter
Width
Radial Thickness
Scraper ring
Diameter
Width
Radial Thickness
Piston Ring Gap
Valve Timing
Inlet valve opens
Exhaust valve closes
9.5 to 1
24 degrees (x") full advance
inner free length 1.531"
outer free length 1.700"
1 to 1
1.24 to 1
1.75 to 1
2.76 to 1
6.5 to 1
8.05 to 1
11.68 to 1
17.97 to 1
K.L.G. FE 220
2¾" (69.85 mm.)
.0625"—.0615"
.112"—.106"
2¾" (69.85 mm.)
.156"—.155"
.112"—.106"
.008"—.013"
40° B.T.D.C. with .010" rocker
40° A.T.D.C. clearance.
6
www.ajs-matchless.info

Chain Sizes
Front chain
Rear chain
Gear Ratios
Internal Ratios
Top
Third
Second
First
Actual Ratios
Top
Third
Second
First
Sprocket Sizes
Engine
Clutch
Final drive
Rear wheel
a" x .225" (73 links)
½" x
.305" (125 links)
1 to 1
1.30 to 1
1.85 to 1
2.92 to 1
6.89 to 1
8.96 to 1
12.75 to 1
20.12 to 1
21 teeth
50 teeth
19 teeth
55 teeth
350 c.c. Lightweight Model
identity
Engine number
Frame number
Cylinder bore
Stroke
Cubic capacity
Carburettor
Type 389/42
Main jet (without air filter)
Main jet (with air filter)
Choke size
Throttle slide
Needle position
Capacities
Petrol tank
Oil capacity
Gear box
Front chain case
Compression Ratio
General
Seat height
Wheelbase
Weight
Ground clearance
Cylinder bore
Nominal size
On the crankcase near engine
plate cowling.
On right hand side of frame head
lug.
72 mm.
85.5 mm.
347 c.c. (21.17 cu. ins.)
Amal Monobloc (12° inclination)
220
220
18"
3½
central (.106) pilot 25
3¼ gallons (12.5 litres)
2½ pints (1.4 litres)
3 pints (1.8 litres)
568 c.c.
6.9 to 1
29.5" (74 cms.)
53" (134.5 cms.)
340 lbs. (154 kilos)
6" (15 cms.)
2.8345 + .0005" – .0005"
7
www.ajs-matchless.info

Piston Size
Skirt diameter (taken at right angle
to gudgeon pin top of the skirt).
High limit
Low limit
Piston Rings
Compression rings
Diameter
Width
Radial Thickness
Scraper ring
Diameter
Width
Radial Thickness
Piston Ring Gap
Ignition Timing
Valve Timing
Inlet valve opens
Exhaust valve closes
Spark Plug
Chain Sizes
Front chain
Rear chain
Gear Ratios
Internal Ratios
TOP
Third
Second
First
Actual Ratios
Top
Third
Second
First
Sprocket Sizes
Engine
Clutch
Final drive
Rear wheel
2.8286"
2.8276"
72 mm.
3/64"
.151"—.109"
72 mm.
E"
.109"—.101"
.008"—.013"
¼" B.T.D.C.
40° B.T.D.C. with .010" rocker
40° A.T.D.C. clearance.
K.L.G. FE 80
.315" x .628" Duplex (72 links)
½" x .305" (123 links)
1 to 1
1.30 to 1
1.85 to 1
2.92 to 1
6.39 to 1
8.32 to 1
11.82 to 1
18.68 to 1
22 teeth
46 teeth
18 teeth
55 teeth
350 c.c. Heavyweight (Long Stroke) Model
Cylinder bore size
Compression ratio (1956 onwards)
Piston skirt diameter—Top
Piston ring gap
Gudgeon pin bush size
2.7197—2.7187"
7.4 to 1
2.7180—2.7172"
.008"—.0013"
d" + .0005"
d" – .00025"
8
www.ajs-matchless.info

Con rod diameter
Crank pin diameter
Crank pin rollers
Valve spring free Length
Valve spring wire diameter
Drive side bearing
high
low
high
low
Timing side bush diameter— in situ
Cam wheel bushes (all)
high
low
Finished bore size for 1964 engine
Carburettor
Type
Bore size
Main jet
Slide
Pilot jet
Needle jet
Needle location
Spark Plug
1.7037"
1.7035"
1.23075"
1.20350"
¼" x ¼"—30
25/64"
.168"
1" x 2¼" x ¾"
1" x 2¼" x s"
1.1255"
1.1250"
s" + .00075"
"57000.–
2.8352—2.834"
376/5
1z"
220 (no air filter)
3½
30
.106
Central notch
K.L.G. FE 80
Cylinder bore size
Compression ratio
Piston skirt diameter—top
Piston Ring Gap
Gudgeon pin bush
Con rod diameter
Crank pin diameter
high
low
high
low
Crank pin rollers (1962—28 rollers)
Valve spring free length
Valve spring wire diameter
Drive side bearings
Cam wheel bushes
Rocker box bushes
Carburettor
2.915"—2.194"
8.5 to 1
2.9163"—2.9055"
.008"—.013"
as 350 c.c. longstroke
1.7037"
1.7035"
1.20375"
1.20350"
as 350 c.c. longstroke
1A"
x"
as 350 c.c. longstroke
as 350 c,c- longstroke
as 350 c.c. longstroke
as 350 c.c. longstroke
Cylinder bore size
Compression ratio
Piston skirt diameter—top
Piston Ring Gap
Valve spring free length
3.2505—3.2495"
7.3 to 1
3.2475—3.2467"
.010"—.015"
25/64"
500 c.c. Heavyweight Model
350 c.c. Heavyweight (Short Stroke) Model
9
www.ajs-matchless.info

Valve spring wire diameter .168"
FOR OTHER DIMENSIONS REFER TO 350 c.c. LONGSTROKE
Carburettor
Type
Bore size
Main jet
Slide
Pilot jet
Needle jet
Needle position
Spark Plug
389/1
1E"
250 (no air filter)
3½
30
.106
Central notch
N4
Cylinder bore size
Compression ratio
Piston skirt diameter—top
Piston Ring Gap
Gudgeon pin bush
Con rod diameter
Crankpin diameter
Crank pin rollers
Valve spring free length
Valve spring wire diameter
Timing side bush diameter
high
low
high
low
high
low
3.2505—3.2495"
8.7 to 1
3.3795—3.7870"
.010—.015"
see 350 details
2.016"
2.01575"
1.5156"
1.5154"
½ x ¼" (14)
1A"
x"
.8757"
.8752"
ALL other dimensions as 350 c.c. engine.—For carburetter details see
500 c.c standard model.
Cylinder bore size high
low
Cubic capacity
Compression ratio
Carburettor1a"choke
Main jet size—with air filter
Main jet size—without air filter
Throttle slide
Air jet
Needle
Ignition Timing
Spark Plug
Gear Ratios
Top
Third
Second
First
3.386"
3.385"
30.5 cu. in. (498 c.c)
12 to 1
Amal 5GP2
290
310
No. 6
.125"
5GP6 (central notch)
33° to 34° full advance
Champion N57R
7.5 to 1
9.1 to 1
12.7 to 1
19 to 1
500 c.c. Scrambler Model
G85 CS Scrambler USA Model and G80 CS
10
www.ajs-matchless.info

1964 to 1966 DATA
Ignition timing with full advance
350 c.c. model
500 c.c. model
500 c.c. Scrambler (8.7 ratio)
Carburettors
350 c.c. model type
main jet size
Slide
Pilot jet
Needle jet
Needle position
500 c.c. model type
main jet size
Slide
Pilot jet
Needle jet
Needle position
34° 8.9 mm.
38° 10.98 mm.
38° 10.98 mm.
389/208
260
3
25
1065
Central notch
389/209
290
3½
25
1065
Central notch
The new chain sizes are:
350 c.c. front
500 c.c. front
350 c.c. rear
500 c.c. rear
68 links
69 links
98 links
99 links
Note—1963/64 models have 18" wheels which affects gear ratios; to
remedy all heavyweight engines have one more tooth on the engine
sprocket.
GEAR RATIOS
Scrambler Models 1957 to 1959
Internal Ratios
First
gear
2.67
Second
gear
1.77
Third
gear
1.35
Fourth
gear (top)
1.1
Sprocket Sizes
Rear wheel
Clutch
Final drive {gear box)
Engine
Chain Sizes
Front chain
Rear chain
Valve lift—inlet cam
Valve lift—exhaust cam
54 teeth
42 teeth
16 teeth
19 teeth
½" x .305" (67 links)
a" x s" (104 links)
.442"
.339"
For all other technical details refer to the 500 c.c. regular Scrambler.
Note—Lubrication system is same as 1964 regular engine.
… …
11
www.ajs-matchless.info

Engine
(A)
(B)
Sprocket
size
16 teeth
17 „
18 „
19 „
20 „
21 „
22 „
First
gear
18.39 to 1
17.30 to 1
16.34 to 1
15.48 to 1
14.71 to 1
14.01 to 1
13.37 to 1
Second
gear
12.19 to 1
11.47 to 1
10.83 to 1
10.26 to 1
9.75 to 1
9.29 to 1
8.86 to 1
Third
gear
9.30 to 1
8.74 to 1
8.26 to 1
7.83 to 1
7.43 to 1
7.08 to 1
6,76 to 1
Fourth
gear (top)
6.89 to 1
6.48 to 1
6.12 to 1
5.80 to 1
5.51 to 1
5.25 to 1
5.01 to 1
(A) Standard for 350 c.c. Scrambler Models.
(B) Standard for 500 c.c. Scrambler Models.
Engine
(A)
(C)
(B)
Sprocket
size
17 teeth
18 „
19 „
20 „
21 „
22 „
First Second
gear gear
16.6 to 1 11.05 to 1
15.65 to 1 10.39 to 1
14.85 to 1 9.86 to 1
14.11 to 1 9.37 to 1
13.42 to 1 8,93 to 1
12.81 to 1 8.52 to 1
Third
gear
7.91 to 1
7.46 to 1
7.07 to 1
6.73 to 1
6.41 to 1
6.11 to 1
Fourth
gear (top)
6.48 to 1
6.12 to 1
5.80 to 1
5.51 to 1
5.25 to 1
5.01 to 1
(A) Standard for 350 c.c. Touring Models.
(B) Standard for 500 c.c. Touring Models.
(C) S/C Engine Sprocket.
Internal Ratios
Engine
(A)
(B)
Sprocket
size
16 teeth
17 „
Standard
18 „
19 „
20 „
21 „
22 „
(A)
(B)
First
gear
3.28
First
gear
22.59 to 1
21.25 to 1
20.07 to 1
19.02 to l
18.07 to 1
17.22 to 1
16.43 to 1
Standard for
Standard for
Second
gear
2.39
Second
gear
16.46 to 1
15.48 to 1
14.62 to 1
13.86 to 1
13.16 to 1
12.54 to 1
11.97 to 1
Third
gear
1.47
Third
gear
10.12 to 1
9.52 to 1
8.99 to 1
8.52 to 1
8.10 to 1
7.71 to 1
7.36 to 1
350 c.c. Trials Models.
500 c.c. Trials Models.
Fourth
gear (top)
1.1
Fourth
gear (top)
6.89 to 1
6.48 to 1
6.12 to 1
5.80 to 1
5.51 to 1
5.25 to 1
5.01 to 1
Clutch 42 teeth
Gear box 16 teeth
Rear wheel 42 teeth
Heavyweight Models 1957-1962
Trials Models
Sprocket sizes.
Clutch 42 teeth
Gear box 16 teeth
Rear wheel 42 teeth
First
gear
2.67to 1
Second
gear
1.77 to 1
Third
gear
1.35 to 1
Fourth
gear (top)
1 to 1
Sprocket sizes.
Internal ratios.
… …
… …
……… …
……… …
……
… …
……… …
……… …
……
12
www.ajs-matchless.info

TABLE OF CHAINS
Chain Sizes (Heavyweight Model)
Front chain
Rear chain
Magneto chain
Dyno chain
½" +.305"
s"+.380"
a"+.225"
a"+.225"
1957 Models
Front
Rear
Magneto
Dyno
350 c.c
67 links
98 „
46 „
50 „
350 c.c
Trials
66 links
97 „
46 „
50 „
500 c.c
68 links
98 „
46 „
50 „
500 c.c
Scrambler
67 links
97 „
46 „
50 „
1958 Models
Front
Rear
Magneto
Dyno
350 c,c
67 links
98 „
46 „
50 „
350 c.c
Trials
66 links
97 „
46 „
50 „
500 c.c
68 links
98 „
46 „
50 „
500 c.c
Scrambler
67 links
97 „
46 „
50 „
1959 Models
Front
Rear
Magneto
350 c.c
67 links
98 „
350 c.c
Trials
66 links
94 „
46 „
500 c.c
68 links
98 „
500 c.c
Scrambler
67 links
97 „
46 „
1960-1962 Models
Front
Rear
Magneto 350 c.c 67 links
98 „
350 c.c
Trials
66 links
94 „
46 „
500 c.c
69 links
98 „
500 c.c
Scrambler
67 links
98 „
ENGINE DESIGN CHANGES
250 c.c. Model
The GSR model was first introduced in 1962 starting with engine
number 12128. The alterations made to the engine were;
(1) Steel flywheel—to replace iron type,
(2) Large diameter crank pin—to allow use of the high compression
piston.
(3) Larger inlet valve similar to the valve used on the lightweight 350
engine to improve volumetric efficiency of the engine.
(4) Engines with number from 12828 have a modified oiling system with
the stroke of the pump altered to increase oil circulation. Earlier
engines cannot be modified as a new crank case is required. With
this system oil was fed to the cam followers for better lubrication.
(5) Compression ratio increased from 8 to 1 to 9.5 to 1 made possible
by the introduction of steel flywheels and the large crank pin for
the big end.
Engine noises. A light rattle audible when running without a load, and
disappearing when the engine is under load, is due to slight movement in
… …… … …… … …… … ……
… …… … …… … …
… ……
… …… … …… … …
… ……
… …… … …… … …
… …… … …… … …
13
www.ajs-matchless.info

the big end assembly. To remedy—providing the roller path on the crank
pin and also the big end eye is not broken—a new set of rollers will take
up the slight movement.
A similar rattle that is not affected by engine load, on engines with a
number before 6850 is due to the stator in the crankcase breather being
loose, this being secured by the steel tube located between the rear of the
crankcase and the gear box. If the tube is broken the stator will move as
the piston travels up and down, causing the rattle. The stator part number
is 04220. On later engines the stator tube was discarded, the stator being
now located by a bolt which will be found below the drive side bearing
on the crankcase.
A rattle in the timing gear is due to wear on the cam followers, due to
excessive rpm causing valve float, or weak valve springs which would
have the same effect.
Excessive oil consumption. When the engine smokes unduly, and if the
cylinder has been rebored with a non standard piston in use, this is usually
due to an inefficient oil scraper ring in use. The Wellworthy DUAFLEX
ring—which is the best oil scraper ring—will cure this fault. In the event
of this type of ring being already in use it is possible that there is some
restriction in the crankcase oil filter causing oil to accumulate in the
crankcase which the oil control ring cannot cope with. To overcome this
possibility a longer crankcase oil filter was introduced and first used on
the 350 lightweight engines, useable for the 250 engine.
Oil can also accumulate in the crankcase if the cap for the filter 042064
is out of position blocking the oil return passage in the compartment for
the filter. If there is no improvement after dealing with the points given
then a rebore is necessary.
Crankcase bearings. Engines made in 1959 used two ball bearings in the
drive side crankcase, which had short life. This was overcome by using
a roller bearing in the drive side crankcase—on the outside—next to the
flywheel, where the maximum load occurs. See para Engine service for
fitting instructions.
Heavyweight Models
1947 MODELS
(1) Improved type oil-pump plunger (two start type) with new timing
side axle (identified by 2S stamped on plunger).
(2) Oil feed passage in timing side half crankcase increased to T"
diameter to prevent cavitation, with corresponding increase in
diameter of the oil pipe ( a"diameter).
(3) A two piece oil pump guide pin x" in diameter to prevent wear on
the pin due to the increased plunger speed.
(4) Shorter connecting rod for centres.
(5) The use of a long plain bush for the timing side bearings; the small
roller bearing is now obsolete. Engines fitted with the old type
bearing can use a modified bush with two external diameters. The
steel sleeve is retained to locate the new bush on the large external
diameter.
1948 MODELS
(1) Annular groove in pump plunger increased from x" to ¼" diameter
14
www.ajs-matchless.info

with suitable guide pin.
(2) Wire-wound pistons fitted to 500 c.c. models.
(3) 500 c.c. type high crankcase used for 350 c.c. models after engine
number 8000.
(4) 500 c.c. flywheels used for the 350 c.c. model.
In addition to these engine design changes;
(5) Larger brakes (7" diameter) were fitted.
1949 MODELS
(1) New type cylinder head with hair-pin valve springs with rocker box
to suit.
(2) Valve lifter transferred from crankcase to rocker box.
(3) Wire-wound pistons for all models.
(4) Longer valves, hardened valve end caps discarded.
(5) New rockers for longer valves, also new valve guides.
1950 MODELS
(1) Alloy cylinder heads and barrels used on Competition models only.
Steel crankpin washer in place of bronze type.
1951 MODELS
(1) Alloy cylinder head used on both touring type engines. Crankpin
washers discarded, flywheels altered.
1952 MODELS
(1) Open tray valve spring seat, prongs for valve springs increased in
length.
(2) Cylinder barrel lengthened 8" on 500 c.c. touring engine, compression
plate discarded.
(3) Recess for driving side bearings in crankcase with two diameters, for
close and easy interference fit to avoid “end loading” of these
bearings.
(4) Top compression ring chrome plated.
1953 MODELS
No change.
1954 MODELS
(1) Oil feed in rocker box modified to increase oil supply to rocker end
of inlet valve and stop valve spring wear.
(2) New rockers for valve ends with groove in side for oil duct.
(3) High-lift cams.
(4) Larger diameter timing side shaft, with flywheel to suit.
(5) Two diameter timing side bush, steel sleeve discarded.
(6) Automatic ignition control on 500 c.c. model.
1955 MODELS
(1) New crankcase to use one small and one large driving side bearing.
(2) New driving side flywheel (keyways at 180°),
(3) Circlip fitted to exhaust valve guide,
1956 MODELS
(1) Cylinder wall oil feed discontinued.
(2) Compression ratio increased to 7.5 for 350 c.c. models, 7.3 for 500 c.c.
models.
(3) Oil tank felt filter deleted and magnetic filter fitted in crankcase.
15
www.ajs-matchless.info

FIG
1
16
www.ajs-matchless.info

FIG
2
17
www.ajs-matchless.info

LUBRICATION
Lightweight Models
This is by true dry sump system. The oil tank, or reservoir, is integral
with the crankcase. The oil pump has only one moving part, i.e., the oil
pump plunger, which rotates and reciprocates. Rotation is created by the
worm gear on the timing side flywheel axle.
Reciprocation is caused by engagement of the oil pump guide pin with
the profiled groove in the oil pump plunger. The oil pump is designed
so that the sump scavenging capacity is greater than the delivery, thus
keeping the crankcase sump free of oil during normal running conditions.
Whilst the oil reservoir is integral with the crankcase, oil is fed to the
pump by gravity, on the same principle as a machine fitted with a separate
oil tank, but without the use of external oil pipes.
Engine oil pump. If, for any reason, the crankcase is dismantled the oil
pump plunger must be removed from its housing before attempting to
separate the crankcase halves. It is also necessary to remove the small
timing pinion.
Important. Under no circumstances must either the pump plunger or
guide screw be disturbed in ordinary routine maintenance.
Engine oil circulation. Provision is made to observe the oil circulating,
which is visible after removing the oil filler cap on the right side of the
crankcase.
The oil pump forces oil through:—
(a) Passages drilled through the timing side flywheel axle, timing side
flywheel and crank pin to lubricate the timing side bearing and the
big-end bearing. The splash passes to interior of cylinder, to lubricate
the cylinder and piston, and then falls into the crankcase sump.
(b) From the front oil pump housing to the rocker box via passages in
the cylinder barrel, lubricating the rocker gear and valve stems. Oil
from the rocker gear drains by gravity via the push rod tunnels to
the timing gear case at a pre-determined level. The over-spill drains
into the crankcase sump.
(c) The oil pump extracts oil from the crankcase sump, metal impurities
are collected by a magnetic filter incorporated in the sump drain
plug. The oil is again filtered by a fabric filter located in the crank-
case, (see Fig. 3) before returning to the oil tank reservoir.
For valve guide lubrication see paragraph "Adjustment of oil feed".
The oil reservoir. The normal oil level is 1 inch below the filler cap orifice,
the oil content is 2½ pints. Run the engine for a short period to scavenge
the sump, before “topping up”.
After the first 500 miles (800 kilometres) again at 1,000 miles (l600
kilometres) and subsequently at 5,000 mile intervals (8000 kilometres) the
oil reservoir should be drained the oil filter cleaned in petrol and the
reservoir replenished with new oil. It is preferable to drain the oil after
a run and when the oil is warm. A drain plug is fitted to both the crank-
case sump also the oil reservoir. The drain plug for the reservoir is close
to the bottom front crankcase bolt.
The crankcase fabric filter. The filter is cylindrical in shape and made
18
www.ajs-matchless.info