Maico MC250, MC400, MC440, MC501 Instruction Book And Service Manual

.

Maico 72-74.5 Radial Manaual

AfAICO

MC250
MC400
MC440

MC501

'"

www.maicowerk.com

Instruction book

Service manual

From January 1974

Courtesy of [e-mail]

CONTENTS

CONTENTS

I.

Preface

Page

3

II.

Technical data

Page 3

III.

Description of the machines

Page 7

A - Motor
B - Chassis

IV.

Service instructions

Page12

A - Preparation for competition use
B - Assembly and repair instructions for engine
C - Assembly and repair instructions for chassis

INDEX OF IllUSTRATIONS

Page

1

Side View - Motorcycle

3

2

Exploded View - Engine (Drawing)

5

3

Cylinder, Piston, Cylinder Head

7

4

Crankshaft, Bearings, Seals

7

5

Primary Drive (Assembled)

8

6

Ignition Complete (Assembled)

8

7

Wiring Diagram

8

8

Small Double-Row Clutch Disassembled

8

g

Transmission with Bearings Disassembled

9

10

Carburetor, Air Cleaner Boot, Air Cleaner Assy

9

11

Frame (Bare)

10

12

Telescopie Forks (Photograph

&

Exploded Drawing)

10

13

Front Wheel (Exploded Drawing)

11

14

Rear Wheel (Exploded Drawing)

11

15

Setting Ignition Timing with Dial Indicator

12

16

Setting

&

Tuning Carburetor

12

17

Clutch Adjustement at the lever

13

18

Changing fork oil (Draining)

14

19

Filling fork oil

14

20

Chain Adjustement

15

21

Master Link

15

22

Piston Disassembly

16

23

Pulling Ignition Magnet

16

24

Clutch Disassembly

16

25

HOlding the Clutchbody with Special HOlding Tool

17

26

Removing the Sprocket on the Crankshaft

17

27

Shimming the layshaft

18

28

Shimming the Crankshaft

18

Maico 72-74.5 Radial Manaual

Preface

I.

Technical data

II.

Description of the machines

III.

A - Motor
B - Chassis

Service instructions

IV.

A - Preparation for competition use
B - Assembly and repair instructions for engine
C - Assembly and repair instructions for chassis

INDEX OF IllUSTRATIONS

Side View - Motorcycle

1

Exploded View - Engine (Drawing)

2

Cylinder, Piston, Cylinder Head

3

Crankshaft, Bearings, Seals

4

Primary Drive (Assembled)

5

Ignition Complete (Assembled)

6

Wiring Diagram

7

Small Double-Row Clutch Disassembled

8
g

Transmission with Bearings Disassembled
Carburetor, Air Cleaner Boot, Air Cleaner Assy

10

Frame (Bare)

11

Telescopie Forks (Photograph

12

Front Wheel (Exploded Drawing)

13

Rear Wheel (Exploded Drawing)

14

Setting Ignition Timing with Dial Indicator

15

&

Setting

16

Clutch Adjustement at the lever

17

Changing fork oil (Draining)

18

Filling fork oil

19

Chain Adjustement

20

Master Link

21

Piston Disassembly

22

Pulling Ignition Magnet

23

Clutch Disassembly

24

HOlding the Clutchbody with Special HOlding Tool

25

Removing the Sprocket on the Crankshaft

26

Shimming the layshaft

27

Shimming the Crankshaft

28

Tuning Carburetor

&

Exploded Drawing)

Page
Page 3
Page 7

Page12

Page

10
10
11
11
12
12
13

14

14
15
15
16
16
16
17
17
18
18

3

3
5
7
7
8
8
8

8
9
9

www.maicowerk.com

Courtesy of [e-mail]

I.

I.

PREFACE

The Maico models MC 250, 400, 450 and 501 CCM are constructed and designed especially for compe-
tition and off-road use. They are suitable for moto-cross and enduro competition, and for crossing any
difficult terrain. The moto-cross models are known for their high horse-power output, special frame
geometry and exceptional light weight. Fore these three qualities to be used fully, the machine must
always be tuned and serviced to the highest degree. These instructions, together with basic mechanical
knowledge will assure trouble free performance.

501 CCM

1

91,6 mm

76

mm

501 ccm

12 : 1

51/6900 RPM

Bing Type V 54

38mm

185

285

40

As Required

440 CCM

400 CCM

250 CCM

Air cooled, Piston Port, 2 Stroke Engine

1 1 1

67 mm 77 mm 82 mm
70 mm 83 mm 83 mm
247 ccm 386 ccm 438 ccm

12:1 12:1 12:1
33/7000 RPM 43/6700 RPM 47/6900 RPM
Bing Type V54 Bing Type V 54 Bing Type V 54

36 mm 36 mm 36 mm

175-180 185 185

280-285 285 285
35 40 40
As Required As Required As Required

1 1/2 Turns As Required

Internal Rotor Magneto Type Appt. MZ 465 With Internal Primary

and External Secondary Ignition Coiis

II. TECHNICAL DATA

Maico MC

Motor:
No. of Cylinders:

Bore:
Stroke:
Displacement

(CCl

Compression Ratio:
Brake Horse-Power (Din)
Carburetor:
Diameter:
Main Jet:
Needle Jet:
Low Speed:
Needle Position:
Idler Air Screw:
Ignition:

Maico 72-74.5 Radial Manaual

PREFACE

The Maico models MC 250, 400, 450 and 501 CCM are constructed and designed especially for compe-
tition and off-road use. They are suitable for moto-cross and enduro competition, and for crossing any
difficult terrain. The moto-cross models are known for their high horse-power output, special frame
geometry and exceptional light weight. Fore these three qualities to be used fully, the machine must
always be tuned and serviced to the highest degree. These instructions, together with basic mechanical
knowledge will assure trouble free performance.

II. TECHNICAL DATA

Maico MC

Motor:

No. of Cylinders:

Bore:
Stroke:
Displacement
Compression Ratio:
Brake Horse-Power (Din)
Carburetor:
Diameter:
Main Jet:
Needle Jet:
Low Speed:
Needle Position:
Idler Air Screw:
Ignition:

(CCl

www.maicowerk.com

250 CCM

Air cooled, Piston Port, 2 Stroke Engine

1 1 1

67 mm 77 mm 82 mm
70 mm 83 mm 83 mm
247 ccm 386 ccm 438 ccm

12:1 12:1 12:1
33/7000 RPM 43/6700 RPM 47/6900 RPM
Bing Type V54 Bing Type V 54 Bing Type V 54
36 mm 36 mm 36 mm

175-180 185 185
280-285 285 285
35 40 40

As Required As Required As Required

1 1/2 Turns As Required
Internal Rotor Magneto Type Appt. MZ 465 With Internal Primary

and External Secondary Ignition Coiis

400 CCM

440 CCM

501 CCM

1

91,6 mm

76

501 ccm

12 : 1

51/6900 RPM

Bing Type V 54

38mm

185

285

40

As Required

mm

Courtesy of [e-mail]

Spark Plug:

Spark Plug:
Type:

In Moist or Cold

Conditions:

Timing Advance:

Points Gap at Top Dead
Center:
Primary Drive:

Primary Drive Ratio:
Clutch:
Transmission:

Champion

Champion

Champion

N2 or N2G

N2 or N2G

N2 or N2G

N3 or N3G

N3 or N3G

N3 or N3G

2.8 to 3.2 mm

3.5 to 3.7 mm

35mm

BTDC

BTDC

BTDC

03mm 0.3mm 03mm
Endless Renold Chain 3/8" x 7/32", 54 Link
Double row Triple row Triple row
39/21

=

1,86 39/21=1,86 39/21=1,86
Multi Plate wet Clutch Driving the Main Shaft
Dog Shifting 4-Speed, Operated by Shift Forks
Optional Close or Wide Ratio

Champion
N2 or N2G

N3 or N3G
3mm
BTDC

0.3mm

Triple row
39/21=1,86

GS

278

179

1.29

1.0

Summer - SAE 90 Or Bel

Gear Ratio:

1. Gear

2. Gear

3. Gear

4. Gear

Gear Oil:

Final Drive:

Frame:

Main Measurements:

Overall length
Overall Heigth

Overall Width
Wheelbase
Steering Head Angle

(Rake)
Trial
Ground Clearance

Front Suspension:
Rear Suspension:

WHEELS:

Front:
Rear:

TIRES:

Front:
Rear

Tire Pressure:

Front Brake:
Rear Brake:
Fuel Tank:
Petcocks:

Air Filter:

MC

199
152
123
10

1 Liter gear oil (1 quart) Winter - SAE 50
Ray Racing Gear Oil (MC5)
Continuous chain 5/8" x 1/4" 120 links

Sprockets: Rear wheel - 59 (521.

Drive shaft - 11, 12, 13 or 14 Tooth as required.

Double-Downtube Lightweight Frame Made of Chrome-Moly Tubing.

2120 mm

1150 mm

850 mm

1400 mm

60 degrees

140 mm

210 mm

Hydraulic dampened telescopie forks with 180 mm travel

Swinging arm with hydraulic shock absorbers.

1.60 x 21" Steel-chromed or aluminum alloy rim.

1.85 x 18" Steel-chromed rim

2.15 x 18" Aluminum alloy rim

3 :00x21"

4 : 00 - 4 :50 x 18"
As required (7 to 12 lbs. per sq. in. I
Drum brake 136 mm diameter
Drum brake 160 mm diameter
Fiberglass or aluninum alloy tank with 5.5 or 8.5 liter capacity.
Two - 3 position petcocks with large flow capacity and built in screen

filter.

Large volume foam air filter in fiberglass air cleaner box.

Maico 72-74.5 Radial Manaual

Type:

In Moist or Cold

Conditions:

Timing Advance:

Points Gap at Top Dead
Center:
Primary Drive:

Primary Drive Ratio:
Clutch:
Transmission:

Gear Ratio:

1. Gear

2. Gear

3. Gear

4. Gear

Gear Oil:

Final Drive:

Frame:
Main Measurements:

Overall length
Overall Heigth
Overall Width

Wheelbase

Steering Head Angle

(Rake)

Trial

Ground Clearance
Front Suspension:
Rear Suspension:

WHEELS:

Front:
Rear:

TIRES:

Front:
Rear

Tire Pressure:

Front Brake:

Rear Brake:
Fuel Tank:
Petcocks:

Air Filter:

www.maicowerk.com

Champion
N2 or N2G

N3 or N3G

2.8 to 3.2 mm
BTDC

03mm 0.3mm 03mm
Endless Renold Chain 3/8" x 7/32", 54 Link
Double row Triple row Triple row
39/21
Multi Plate wet Clutch Driving the Main Shaft
Dog Shifting 4-Speed, Operated by Shift Forks

Optional Close or Wide Ratio

1 Liter gear oil (1 quart) Winter - SAE 50
Ray Racing Gear Oil (MC5)
Continuous chain 5/8" x 1/4" 120 links
Sprockets: Rear wheel - 59 (521.

Double-Downtube Lightweight Frame Made of Chrome-Moly Tubing.

=

1,86 39/21=1,86 39/21=1,86

Drive shaft - 11, 12, 13 or 14 Tooth as required.

Champion
N2 or N2G

N3 or N3G

3.5 to 3.7 mm
BTDC

2120 mm

1150 mm

850 mm

1400 mm

60 degrees

140 mm

210 mm

Hydraulic dampened telescopie forks with 180 mm travel

Swinging arm with hydraulic shock absorbers.

1.60 x 21" Steel-chromed or aluminum alloy rim.

1.85 x 18" Steel-chromed rim

2.15 x 18" Aluminum alloy rim

Champion
N2 or N2G

N3 or N3G
35mm
BTDC

MC

199
152
123
10

Summer - SAE 90 Or Bel

Champion
N2 or N2G

N3 or N3G
3mm
BTDC

0.3mm

Triple row
39/21=1,86

GS

278

179

1.29

1.0

3 :00x21"

4 : 00 - 4 :50 x 18"
As required (7 to 12 lbs. per sq. in. I
Drum brake 136 mm diameter
Drum brake 160 mm diameter
Fiberglass or aluninum alloy tank with 5.5 or 8.5 liter capacity.
Two - 3 position petcocks with large flow capacity and built in screen

filter.

Large volume foam air filter in fiberglass air cleaner box.

Courtesy of [e-mail]

••

••

...

"'--

"
"

,,---

35----

"

"

••

53

15 ~

::

.

\

~\

.'D

20

'"
'"

"

••

"

••

Maico 72-74.5 Radial Manaual

••

••

...

"'--

"
"

,,---

35----

15 ~

::

.

\

"

"

••

53

~\

.'D

20

'"
'"

www.maicowerk.com

"

••

••

"

Courtesy of [e-mail]

III. DESCRIPTION OF THE MACHINES

III. DESCRIPTION OF THE MACHINES

The Maico MC 250, 400, 440 and 501 ccm Motorcycles are very high performance competition motor-
cycles which are designed for off-road use in difficult terrain or on a moto-cross race track.

A. MOTOR

1. CYLINDER

The cyl inder is a special moto-cross cyl inder con-
structed of a light alloy material with a shrunken
cylinoer sleeve. The cooling fins are arranged
radially for better cooling even at low speeds. The
cylinder is fastened to the crank casesby four
8 x 28 mm studs. Between the cylinder and main
casesis a paper gasket 0.3 mm thick.

2. CYLINDER HEAD

Is also constructed of a light alloy material. The
cooling fins are again arranged radially with five-
8 mm or 10 mm studs mounting it to the cylin-
der. The cylinder head gasket is made of soft cop-
per (0.6 mm thick).

3. Cylinder piston, Cylinder head

3. THE PISTON

440 CC
8195

82.10
8225

to 83.00

400 CC
7695

77.10

77.25

t078.00

250 CC

66.95

67.10

67.25

to 68.00

The MAHLE piston is forged of a special piston alloy containing a large amount of silicon. With "L"

shaped piston ring in the 250, 440 and 501. An "L" shaped and a rectangular piston ring is used in the

400. The piston clearance in the cylinder measures 0.05 to 0.07 mm. The piston oversizes are available
in approximately 0.15 mm intervals .

Example:

Std.

1st over

2nd over

Pistons other than MAH LE are not recommended.

4. CRANKSHAFT AND CONNECTING ROD

The crankshaft halves are turned on a lathe from

rough forgings. After careful machine finishing,

they are heat treated for better case hardening

(they are also tempered after being heat treated).

The right half or magneto half is tapered. The
left half has a key way or splines to attach the
primary drive sprocket. The connecting rod is
forged aswell. The journal for the needle bea.
rings is caged. The radial play of the big end
bearing is 0.03 mm to 0.04 mm. The play of the

wrist pin to the wrist pin bearing is 0.002 to

0.005 mm.

4. Crankshaft, Bearings, Seals

Maico 72-74.5 Radial Manaual

The Maico MC 250, 400, 440 and 501 ccm Motorcycles are very high performance competition motor-

cycles which are designed for off-road use in difficult terrain or on a moto-cross race track.

A. MOTOR

1. CYLINDER

The cyl inder is a special moto-cross cyl inder con-
structed of a light alloy material with a shrunken
cylinoer sleeve. The cooling fins are arranged

radially for better cooling even at low speeds. The
cylinder is fastened to the crank casesby four
8 x 28 mm studs. Between the cylinder and main
casesis a paper gasket 0.3 mm thick.

2. CYLINDER HEAD

Is also constructed of a light alloy material. The

cooling fins are again arranged radially with five-

8 mm or 10 mm studs mounting it to the cylin-
der. The cylinder head gasket is made of soft cop-

per (0.6 mm thick).

3. Cylinder piston, Cylinder head

3. THE PISTON

The MAHLE piston is forged of a special piston alloy containing a large amount of silicon. With "L"
shaped piston ring in the 250, 440 and 501. An "L" shaped and a rectangular piston ring is used in the

400. The piston clearance in the cylinder measures 0.05 to 0.07 mm. The piston oversizes are available

in approximately 0.15 mm intervals .

Example:
Std.

1st over
2nd over

Pistons other than MAH LE are not recommended.

4. CRANKSHAFT AND CONNECTING ROD

The crankshaft halves are turned on a lathe from
rough forgings. After careful machine finishing,
they are heat treated for better case hardening

(they are also tempered after being heat treated).
The right half or magneto half is tapered. The
left half has a key way or splines to attach the
primary drive sprocket. The connecting rod is
forged aswell. The journal for the needle bea.
rings is caged. The radial play of the big end
bearing is 0.03 mm to 0.04 mm. The play of the

wrist pin to the wrist pin bearing is 0.002 to

0.005 mm.

250 CC

66.95

67.10

67.25

to 68.00

www.maicowerk.com

400 CC
7695

77.10

77.25

t078.00

4. Crankshaft, Bearings, Seals

440 CC
8195

82.10
8225

to 83.00

Courtesy of [e-mail]

5. PRIMARY DRIVE

Maico 72-74.5 Radial Manaual

The primary drive from the crankshaft to the
clutch is by means of a double-row chain 3/8" x

7/32"

x
an endless type and has 54 links. The manufac-
ture is RENOLD. Other brand chains are not
recommended.

7/32"

in the MC

in the

250

and a triple-row chain

400, 440

n

•

and

501.

The chain is

3/8"

6. MAGNETO. IGNITION COILS

The Magneto. an APPT MZ 65 rotates in the
same direction as the motor cycle moves. It is
attached to the right crankshaft on a tapered
outer journal. A 4 mm screw determines the

proper position of the magnet. The primary
coil, condensor and contact breaker are moun-
ted on the stator. The main coil is mounted
under the fuel tank and fastened to the frame.
The manufacturer is PRUFEX
BOSCH

#

PA

0221500800.

#

BZ

140/1,

or

5. Primary drive

7. CLUTCH

The clutch is attached to the transmission main

shaft. It is an oilbath clutch which is built in three
different models. The MC

is used in conjunction with the double row prima-

ry chain. It has six toothed outer clutch plates

which are 99 mm in diameter and the final outer

clutch plate which has a cork facing. Eighten
stacked saucer type springs are used with the

and

440.

There is a choice of two different clut-

ches. The smaller unit with 99 mm diameter

plates and a triple link chain, or the unit with

119 mm diameter plates, also triple link chain.

The MC 501 comes with the larger diameter unit
only.

Small Diameter Clutch:
Six outer toothed plates and six inside toothed
plates without any facing and one outside plate
with a cork facing and one pressure plate locked
with 2 rings. Twenty saucer type springs stacked
in series of 2.

Large Diameter Clutch:
Six outer toothed plates with a cork facing and
five inner toothed plates without facing. Twenty
saucer type springs stacked singly. () ()

250

has a clutch which

400

6. Ignition compl.

7. Wiring Diagram

00

8. Small Duplex clutch Disassercbled

www.maicowerk.com

Courtesy of [e-mail]

8.

GEARBOX

The gearbox is a dog shifting type 4 speed with 2 shift forks and a shifting cam. It is available in two
different ratios, the wide ratio, which is used mainly for Enduro type competition and the close ratio,
which is used for moto-cross competition. On the output drive shaft is the primary final drive sprocket.

It is available in sizes that range from 11 to 14 teeth, for 5/8" x 1/4" chain.

9.

SHIFT LINKAGE

The shifting of the transmission is by a foot ope.

rated shift lever, moving a shift shaft (In the

left side primary cover). The function of the re-
maining components (Pull rod, hook ratchet,
and shift cam) results in selecting the various
gearswith 2 shift forks. These shift forks are
produced of the highest qual ity steel.

9. Transmission with Bearings Disassembled

10. CARBURETOR. AIR CLEANER

The carburetor is a concentric type V 54 36 iZ>or
38 iZ>m m (On the 501 ) wh ich is attached to the
cylinder with a flexible rubber hose. The only
difference in carburetors is the setting. The air
filter is a micro filter available either in paper

(KNECHT NO: E 426/1) or foam replacement
(FI LTRON) which is located in a air box under

the seat.

10. Carburetor, Air Cleaner
Boot, Air Cleaner Assy

11. EXHAUST SYSTEM

The exhaust systems are specially designed, and

when changed or altered, there will most likely

be a decrease in horse-power and performance.
There are 2 different types of systems available
for each model.
A. Unmuffled - Moto-cross - Competition
B. Muffled . App. 94 Decibel muffled

(For export to USA)

There is a considerable difference between the
MC 250 exhaust system and the 400, 450 and
501 exhaust system.

8.

GEARBOX

The gearbox is a dog shifting type 4 speed with 2 shift forks and a shifting cam. It is available in two
different ratios, the wide ratio, which is used mainly for Enduro type competition and the close ratio,
which is used for moto-cross competition. On the output drive shaft is the primary final drive sprocket.

It is available in sizes that range from 11 to 14 teeth, for 5/8" x 1/4" chain.

9.

SHIFT LINKAGE

The shifting of the transmission is by a foot ope.

rated shift lever, moving a shift shaft (In the

left side primary cover). The function of the re-
maining components (Pull rod, hook ratchet,
and shift cam) results in selecting the various
gearswith 2 shift forks. These shift forks are
produced of the highest qual ity steel.

9. Transmission with Bearings Disassembled

10. CARBURETOR. AIR CLEANER

The carburetor is a concentric type V 54 36 iZ>or
38 iZ>m m (On the 501 ) wh ich is attached to the
cylinder with a flexible rubber hose. The only
difference in carburetors is the setting. The air
filter is a micro filter available either in paper

(KNECHT NO: E 426/1) or foam replacement
(FI LTRON) which is located in a air box under

the seat.

10. Carburetor, Air Cleaner
Boot, Air Cleaner Assy

11. EXHAUST SYSTEM

The exhaust systems are specially designed, and

when changed or altered, there will most likely

be a decrease in horse-power and performance.
There are 2 different types of systems available
for each model.
A. Unmuffled - Moto-cross - Competition
B. Muffled . App. 94 Decibel muffled

(For export to USA)

There is a considerable difference between the
MC 250 exhaust system and the 400, 450 and
501 exhaust system.

Maico 72-74.5 Radial Manaual

www.maicowerk.com

Courtesy of [e-mail]

B. CHASSIS

B. CHASSIS

1. FRAME

The double-down tube frame is made of high

quality chrome moly tubing. The welds are par-

tially welded with the heli-arc principle and par-
tially welded with acetylene and oxygen. Espe-
cially on areas subjected to high stress often
found in moto-cross competition.

2. TELESCOPIE FRONT FORKS

The telescopie forks with hydraulic dampening
have 180 mm of travel. The springs are mounted
externally on the fork tubes and are covered with
rubber fork boots. The hydraulic shocks are moun-
ted in the fork sliders. and have optimal dampe-
ning characteristics:

Each fork tube is filled with 230 cc (7.2 fl. oz.)
of fork oil. The fork tubes are sealed on top with
plugs containing air escape valves. whose proper
functioning is essential.

3. SWINGING ARM - REAR SUSPENSION

The swing arm has a very wide bushing surface

with two rubber-metal bushings. Either Girling
or Koni springs and shocks are available. The

shocks dampening characteristics are especially

developed for Maico.

4. SEAT

The seat is a one-man seat specially fitted and

developed after years of moto-cross sport. Spe-
cial care was taken selecting the composition of
the foam rubber in the seat for maximum com-
fort.

5. FUEL TANK

The fuel tank (fiberglass or aluminium alloy) is
shock-mounted on the frame with soft rubber
bushings. Two petcocks provide a large volume
of fuel flow.

6. FOOT PEGS

The foot pegs are short, spring loaded folding
moto-cross foot pegs without rubber covers.

11. Frame (Bare)

12. Telescopie Fork

7.

HANDLE BARS AND CONTROL LEVERS

The handle bar is made of high quality 22 mm (7/8") diameter chromed tubing, strengthened with a

cross bar. The control levers and twist grip are made by Magura. The clutch and brake lever are made
of cast aluminium alloy with a ball on the ends for safety. The twist grip, also made by Magura, is made
of plastic with 80 degress of turning movement with the 36 mm carbo All cables are coated with Teflon
for minimum friction.

Maico 72-74.5 Radial Manaual

1. FRAME

The double-down tube frame is made of high
quality chrome moly tubing. The welds are par-
tially welded with the heli-arc principle and par-
tially welded with acetylene and oxygen. Espe-

cially on areas subjected to high stress often

found in moto-cross competition.

2. TELESCOPIE FRONT FORKS

The telescopie forks with hydraulic dampening
have 180 mm of travel. The springs are mounted
externally on the fork tubes and are covered with
rubber fork boots. The hydraulic shocks are moun-
ted in the fork sliders. and have optimal dampe-
ning characteristics:

Each fork tube is filled with 230 cc (7.2 fl. oz.)
of fork oil. The fork tubes are sealed on top with
plugs containing air escape valves. whose proper
functioning is essential.

3. SWINGING ARM - REAR SUSPENSION

The swing arm has a very wide bushing surface
with two rubber-metal bushings. Either Girling
or Koni springs and shocks are available. The

shocks dampening characteristics are especially
developed for Maico.

4. SEAT

The seat is a one-man seat specially fitted and
developed after years of moto-cross sport. Spe-
cial care was taken selecting the composition of
the foam rubber in the seat for maximum com-
fort.

5. FUEL TANK

The fuel tank (fiberglass or aluminium alloy) is
shock-mounted on the frame with soft rubber
bushings. Two petcocks provide a large volume
of fuel flow.

6. FOOT PEGS

The foot pegs are short, spring loaded folding
moto-cross foot pegs without rubber covers.

11. Frame (Bare)

12. Telescopie Fork

7.

www.maicowerk.com

HANDLE BARS AND CONTROL LEVERS

The handle bar is made of high quality 22 mm (7/8") diameter chromed tubing, strengthened with a
cross bar. The control levers and twist grip are made by Magura. The clutch and brake lever are made
of cast aluminium alloy with a ball on the ends for safety. The twist grip, also made by Magura, is made
of plastic with 80 degress of turning movement with the 36 mm carbo All cables are coated with Teflon

for minimum friction.

Courtesy of [e-mail]

8. FENDERS

8. FENDERS

The front fender is rubber-mounted on the lower triple clamp. The rear fender is also rubber-mounted
under the seat and on the rear frame member. Both fenders are made from vibration resistant fiberglass.

9. FRONT WHEEL

The rim is available in either chromed steel or
aluminium alloy. The measurements are 1.60 x
21 ". The tire is 3.00 x 21" - mota cross with a
rim lock to keep the tire from spinning on the

rim. The front hub (drum brake) is made of cast
aluminium alloy. with a cast-in steel brake drum
ring. The brake diameter is

1360mm 18 spokes M 4 x 243 mm

18 spokes M 4 x 230 mm
On the small end of the hub is a reinforcing ring
made of aluminium alloy for strength.

13. F rant Wheel

10. REAR WHEEL

This rim is also available in chromed steel. size

1.85 x 18". or aluminium alloy. size 2.15 x 18".
The tire is either a 4.00 or 4.50 x 18" - mota
cross type with one rim lock to secure the tire
to the rim. The rear hub is steel made with a

cast-in brake drum, 160 mm diameter with a large

recession for heavy duty bearings especially for
mota cross. The brake shoes are forged of mag-

nesium with epoxied brake linings.

18 spokes M 4 x 143 mm
18 spokes M 4 x 208 mm

The rear brake is operated with the right foot by
a forged aluminium alloy foot lever connected
with a steel brake rod.

14. Rear Wheel

Maico 72-74.5 Radial Manaual

The front fender is rubber-mounted on the lower triple clamp. The rear fender is also rubber-mounted
under the seat and on the rear frame member. Both fenders are made from vibration resistant fiberglass.

9. FRONT WHEEL

The rim is available in either chromed steel or
aluminium alloy. The measurements are 1.60 x
21 ". The tire is 3.00 x 21" - mota cross with a
rim lock to keep the tire from spinning on the

rim. The front hub (drum brake) is made of cast
aluminium alloy. with a cast-in steel brake drum
ring. The brake diameter is

1360mm 18 spokes M 4 x 243 mm

18 spokes M 4 x 230 mm
On the small end of the hub is a reinforcing ring
made of aluminium alloy for strength.

13. F rant Wheel

10. REAR WHEEL

This rim is also available in chromed steel. size

1.85 x 18". or aluminium alloy. size 2.15 x 18".
The tire is either a 4.00 or 4.50 x 18" - mota
cross type with one rim lock to secure the tire
to the rim. The rear hub is steel made with a

cast-in brake drum, 160 mm diameter with a large

recession for heavy duty bearings especially for
mota cross. The brake shoes are forged of mag-

nesium with epoxied brake linings.

18 spokes M 4 x 143 mm
18 spokes M 4 x 208 mm

The rear brake is operated with the right foot by
a forged aluminium alloy foot lever connected
with a steel brake rod.

14. Rear Wheel

www.maicowerk.com

Courtesy of [e-mail]

IV. SERVICE INSTRUCTIONS

15. Setting Ignition Timing with Dial
Indicator

IV. SERVICE INSTRUCTIONS

A. PREPARATION FOR COMPETITION USE

1. TIMING

Tools needed for setting the timing are a dial indicator, feeler gauge, and a buzz box or circuit breaker

light. The dial indicator is either screwed into the vertical spark plug hole or mounted to one of the

cylinder head studs with a special fastening plate, if the head is removed. The points gap should be set
at .3 mm at top dead center, measured with the feeler gauge.

Next, the crank shaft is rotated approximately
45° counter clockwise. The crank shaft is then
slowly rotated clockwise until the dial shows

2.8 - 3.2 mm before top dead center for the MC
250 or 501, or 3.5 - 3.7 mm for the MC 400 and

440. The ignition points should just open at these
settings. If this is not the case, then the three
screws holding the stator plate in place should be

loosened and the stator plate should be rotated
until the ignition points open at the above settings
This should be checked with the buzz box or cir-

cuit breaker light. One lead is grounded and the

other lead is connected to the ignition points.
The stator plate is then rotated counter clockwise
to achieve more spark advance and it is turned
clockwise to achieve lessspark advance. When the

proper amount of advance is found and the igni-
tion points break the circuit at the previously
mentioned settings, then the screws holding the
stator plate in position should be re-tightened

evenly to prevent the timing from slipping while

tightening the screws. The spark advance should
be double-checked after screws are tightened to

assure proper timing.

2. ADJUSTMENT OF CARBURETOR

The basic adjustmnet jetting of the carburetor is
shown in the technical data. Idle adjustment is
performed while engine is warm with twist grip
closed. It is regulated by moving the carb-slide
while throttle is closed with the larger screw on
the left side of the carbo The farther it is turned
in (clockwise), the higher the idle. The mixture
at idling R.P.M. is regulated with the air adjust-
ment screw which is located directly behind the
idle adjustment screw. The more this screw is
turned in (clockwise), the richer the mixture.
The basic setting should be 1ito 2 turns out
(counter clockwise) from the point where the
screw is bottomed out. Each engine must be indi-
vidually jetted and adjusted.
Other factors to be considered when jetting car-
buretors are humidity, altitude, type of fuel and

mixture ratio. etc. Jetting should always start
with the larger jet sizes and then work down from
there to prevent seizure. With proper jetting, the
spark plug should have a tobacco brown color.

(The spark plug MUST be the proper heat rangel)

16. Setting

U.

Tuning Carburetor

Maico 72-74.5 Radial Manaual

A. PREPARATION FOR COMPETITION USE

1. TIMING

Tools needed for setting the timing are a dial indicator, feeler gauge, and a buzz box or circuit breaker
light. The dial indicator is either screwed into the vertical spark plug hole or mounted to one of the
cylinder head studs with a special fastening plate, if the head is removed. The points gap should be set
at .3 mm at top dead center, measured with the feeler gauge.
Next, the crank shaft is rotated approximately
45° counter clockwise. The crank shaft is then
slowly rotated clockwise until the dial shows

2.8 - 3.2 mm before top dead center for the MC
250 or 501, or 3.5 - 3.7 mm for the MC 400 and

440. The ignition points should just open at these
settings. If this is not the case, then the three
screws holding the stator plate in place should be
loosened and the stator plate should be rotated
until the ignition points open at the above settings
This should be checked with the buzz box or cir-
cuit breaker light. One lead is grounded and the
other lead is connected to the ignition points.
The stator plate is then rotated counter clockwise
to achieve more spark advance and it is turned
clockwise to achieve lessspark advance. When the
proper amount of advance is found and the igni-
tion points break the circuit at the previously
mentioned settings, then the screws holding the
stator plate in position should be re-tightened
evenly to prevent the timing from slipping while
tightening the screws. The spark advance should
be double-checked after screws are tightened to
assure proper timing.

15. Setting Ignition Timing with Dial
Indicator

2. ADJUSTMENT OF CARBURETOR

The basic adjustmnet jetting of the carburetor is

shown in the technical data. Idle adjustment is

performed while engine is warm with twist grip

closed. It is regulated by moving the carb-slide

while throttle is closed with the larger screw on

the left side of the carbo The farther it is turned

in (clockwise), the higher the idle. The mixture

at idling R.P.M. is regulated with the air adjust-

ment screw which is located directly behind the
idle adjustment screw. The more this screw is
turned in (clockwise), the richer the mixture.
The basic setting should be 1ito 2 turns out

(counter clockwise) from the point where the
screw is bottomed out. Each engine must be indi-

vidually jetted and adjusted.

Other factors to be considered when jetting car-
buretors are humidity, altitude, type of fuel and
mixture ratio. etc. Jetting should always start

with the larger jet sizes and then work down from
there to prevent seizure. With proper jetting, the
spark plug should have a tobacco brown color.

(The spark plug MUST be the proper heat rangel)

16. Setting

U.

Tuning Carburetor

www.maicowerk.com

Courtesy of [e-mail]

Petcocks

In the two petcocks are screens to prevent dirt from entering the float bowl. These screensmust be

cleaned regularly. Caution - Only large volume petcocks can be used for adequate fuel flow.

3. AIR FILTER

Before each race the air filter should be checked and cleaned. A paper filter should be cleaned from the

inside out, using compressed air. The foam filter is washed in gasoline or solvent. Then, the foam filter
should be penetrated thoroughly with motor oil (SAE 201, and both ends of either filter smeared with
grease for sealing. Before re-installation of the filter, the inside of the air cleaner box should also be
cleaned. The rubber boot leading to the carburetor should be checked to seethat it is sealed properly.

4. CLUTCH, PRIMARY CHAIN - GEAR BOX

The clutch is checked by actual operation. The
springs will eventually have to be replaced or the
clutch plates will be replaced if there is excessive

slippage. The clutch handlebar lever is adjusted
so that there is 2 to 3 mm play in it. (.080" to
.120"). The primary chain is checked for excess
play. The magnetic drain plug is cleaned every
time the oil is changed to see if any broken rol-
lers from the chain are attached. Replace any de-
fective parts immediately.

17. Clutch adjustment at the lever

5. CYLINDER AND PISTON

The play between piston and cylinder wall should be checked with a feeler gauge. The same should be

done to the piston ring end gap to assuregood compression. A softened head gasket should be installed
and the cylinder head bolts tightened to 18 foot pounds.

6, CRANK SHAFT

While the cylinder is not on the crankcases the play in the lower connecting rod bearing should be
checked.

7. FRAME

The frames are free of maintenance. The steering head welds should be checked for cracks. If a crack is

discovered, the frame should be welded by a qualified welder. The steering head bearing races should be

inspected regularly for signs of rust or abrasions.

8. TELESCOP FORKS - STEERING

Changing fork oil - The upper triple clamp pinch bolts (8 mm Allen) must be loosened, also remove the
air escape caps (36 mm). Next, the caps (27 mm) at the very bottom of the forks are loosened to remove
fork oil. After a thorough flushing of the forks with

solvent or gas the bottom caps (the threads should be
oiledl are re-tightened and 230 cc (7.2 fl. oz.) of fork oil is poured into each fork tube. The upper caps
are then re-installed and the upper pinch bolts are re-tightened. Much care shou ld be given to the forks,
for if the forks don't work properly, the rider cannot perform to the best of his ability.
Service - Front forks - After loosening the pinch bolts, both fork tubes should be taken out of the
triple clamps. The play in the steering head bearings should then be checked and adjusted. The individual
tubes are checked to seeif they are bent. The fork slider is slid up and down on the fork tube in an up

and down motion to see if there is any binding on either the tube or the slider The fork tubes must also

be checked visually for scars and scratches. The fork sealsshould be replaced if there is any leakage.

Petcocks

In the two petcocks are screens to prevent dirt from entering the float bowl. These screensmust be

cleaned regularly. Caution - Only large volume petcocks can be used for adequate fuel flow.

3. AIR FILTER

Before each race the air filter should be checked and cleaned. A paper filter should be cleaned from the
inside out, using compressed air. The foam filter is washed in gasoline or solvent. Then, the foam filter

should be penetrated thoroughly with motor oil (SAE 201, and both ends of either filter smeared with

grease for sealing. Before re-installation of the filter, the inside of the air cleaner box should also be

cleaned. The rubber boot leading to the carburetor should be checked to seethat it is sealed properly.

4. CLUTCH, PRIMARY CHAIN - GEAR BOX

The clutch is checked by actual operation. The
springs will eventually have to be replaced or the
clutch plates will be replaced if there is excessive
slippage. The clutch handlebar lever is adjusted
so that there is 2 to 3 mm play in it. (.080" to
.120"). The primary chain is checked for excess
play. The magnetic drain plug is cleaned every
time the oil is changed to see if any broken rol-
lers from the chain are attached. Replace any de-
fective parts immediately.

17. Clutch adjustment at the lever

5. CYLINDER AND PISTON

The play between piston and cylinder wall should be checked with a feeler gauge. The same should be
done to the piston ring end gap to assuregood compression. A softened head gasket should be installed

and the cylinder head bolts tightened to 18 foot pounds.

6, CRANK SHAFT

While the cylinder is not on the crankcases the play in the lower connecting rod bearing should be
checked.

7. FRAME

The frames are free of maintenance. The steering head welds should be checked for cracks. If a crack is

discovered, the frame should be welded by a qualified welder. The steering head bearing races should be

inspected regularly for signs of rust or abrasions.

8. TELESCOP FORKS - STEERING

Changing fork oil - The upper triple clamp pinch bolts (8 mm Allen) must be loosened, also remove the
air escape caps (36 mm). Next, the caps (27 mm) at the very bottom of the forks are loosened to remove
fork oil. After a thorough flushing of the forks with

solvent or gas the bottom caps (the threads should be
oiledl are re-tightened and 230 cc (7.2 fl. oz.) of fork oil is poured into each fork tube. The upper caps
are then re-installed and the upper pinch bolts are re-tightened. Much care shou ld be given to the forks,
for if the forks don't work properly, the rider cannot perform to the best of his ability.
Service - Front forks - After loosening the pinch bolts, both fork tubes should be taken out of the
triple clamps. The play in the steering head bearings should then be checked and adjusted. The individual
tubes are checked to seeif they are bent. The fork slider is slid up and down on the fork tube in an up

and down motion to see if there is any binding on either the tube or the slider The fork tubes must also

be checked visually for scars and scratches. The fork sealsshould be replaced if there is any leakage.

Maico 72-74.5 Radial Manaual

www.maicowerk.com

Courtesy of [e-mail]

Next, the air release valves, located in the top oil filler caps, should be checked by compressing forks and
observing air pressure release. The fork should return to its original position. If this is not the case, one
must countersink the seating of the ball (for the air release valve) lightly, (app. 150°- 160°). The surface
should have no grooves. Otherwise the ball should be tapped into the seat lightly. During re-assembly of

the forks, care must be taken that there is no pressure on the fork tubes or sliders after re-tightening the
fork pinch bolts and the front axle.

18. Changing Fork oil (Draining)

19. Filling Fork oil

9. REAR WHEEL SUSPENSION

The rear wheel suspension is produced by a swinging arm which is attached to the frame with rubber
bushings and either Girling or Koni shocks. A properly functioning rear suspension gives maximum perfor-
mance in difficult terrain. It is important to have both shock absorbers adjusted to produce the same dam-
pening. The bushings of the swing arms should be checked for play. (Worn bushings MUST be replaced).
A I ight yellow or brown color on the dampening rods of the shocks is proof of too much load on the
shock absorbers. The swingarm bushings should be replaced if necessary. Also, a warped or bent swing-

arm should be replaced.

Mounting of Koni shock absorbers

1. The retainin9 clips and springs on original shocks must be removed.

2. The bottom spring retainer is put on its lowest setting (Three different adjustments are possible.)

3. The shock rod is extended completely and the original spring is slipped over the shock body oil reser-

voir.

4. The spring is compressed and the retaining clips are slipped into position.

5. The top and bottom shock eyes are al igned by rotation of the top eye

Dampening Adjustment of Koni Shocks

In all Koni ("0" series) shocks the dampening is adjustable. When they are obtained from the Koni fac-

tory they are set on the lowest adjustment, and can be mounted immediately. I f stronger dampening

is desired, the shocks dampening can be adjusted. The spring preload can also be adjusted to a stronger

setting. The adjustment of the shock from extremely soft to extremely hard is in 6 different steps, as

follows:

1. Remove the complete shock and remove the spring and clips.

2. Extend the shock rod

completely and push the rubber bumper to the bottom. If the bumper sticks,

pry it loose with a screwdriver. The retainer nut (19 mm) is then loosened by securing the top shock

eye with a screwdriver or in a vice. The eye, retainer nut, and rubber bumper are then removed. Also

remove the alurnlnum spacer and do not rB-lnstall it. This will result in 1/.3

me",?

shock travel.

Next, the air release valves, located in the top oil filler caps, should be checked by compressing forks and

observing air pressure release. The fork should return to its original position. If this is not the case, one

must countersink the seating of the ball (for the air release valve) lightly, (app. 150°- 160°). The surface
should have no grooves. Otherwise the ball should be tapped into the seat lightly. During re-assembly of
the forks, care must be taken that there is no pressure on the fork tubes or sliders after re-tightening the

fork pinch bolts and the front axle.

18. Changing Fork oil (Draining)

19. Filling Fork oil

9. REAR WHEEL SUSPENSION

The rear wheel suspension is produced by a swinging arm which is attached to the frame with rubber
bushings and either Girling or Koni shocks. A properly functioning rear suspension gives maximum perfor-
mance in difficult terrain. It is important to have both shock absorbers adjusted to produce the same dam-

pening. The bushings of the swing arms should be checked for play. (Worn bushings MUST be replaced).
A I ight yellow or brown color on the dampening rods of the shocks is proof of too much load on the
shock absorbers. The swingarm bushings should be replaced if necessary. Also, a warped or bent swing-

arm should be replaced.

Mounting of Koni shock absorbers

1. The retainin9 clips and springs on original shocks must be removed.

2. The bottom spring retainer is put on its lowest setting (Three different adjustments are possible.)

3. The shock rod is extended completely and the original spring is slipped over the shock body oil reser-

voir.

4. The spring is compressed and the retaining clips are slipped into position.

5. The top and bottom shock eyes are al igned by rotation of the top eye

Dampening Adjustment of Koni Shocks

In all Koni ("0" series) shocks the dampening is adjustable. When they are obtained from the Koni fac-

tory they are set on the lowest adjustment, and can be mounted immediately. I f stronger dampening

is desired, the shocks dampening can be adjusted. The spring preload can also be adjusted to a stronger

setting. The adjustment of the shock from extremely soft to extremely hard is in 6 different steps, as

follows:

1. Remove the complete shock and remove the spring and clips.

2. Extend the shock rod

completely and push the rubber bumper to the bottom. If the bumper sticks,

pry it loose with a screwdriver. The retainer nut (19 mm) is then loosened by securing the top shock

eye with a screwdriver or in a vice. The eye, retainer nut, and rubber bumper are then removed. Also

remove the alurnlnum spacer and do not rB-lnstall it. This will result in 1/.3

me",?

shock travel.

Maico 72-74.5 Radial Manaual

www.maicowerk.com

Courtesy of [e-mail]

3. The retainer nut and eye are replaced and re-tightened. The shock rod is pushed all the way to the

3. The retainer nut and eye are replaced and re-tightened. The shock rod is pushed all the way to the
bottom and rotated clockwise until it engages and drops into the shock adjustment slots. When the
rod is rotated to the extreme counter-clockwise position, the shock is on the lightest setting.

4. There are five, half-revolution adjustments possible for dampening. We suggest for the first adjust-
ment, 2 to 3 half turns clockwise is ample. This is achieved by rotating the shock rod clockwise while

engaged in the adjustment slots.

5. The shock rod must then be pulled out without rotating it, to release it from the adjustment mecha-

nism.

6. The shock can then be re-assembled in reverse order. Be sure to re-install the rubber bumper. Failing

to do so can seriously damage the shock under use. Pay special attention that the right and left shock

are adjusted equally. This will result in maximum performance of the Koni shocks.

10, WHEELS

The wheels must be centered carefully and exactly. All spokes must be free of damage and adjusted equally
very often. The wheel bearings are checked for play and being sealed from outside elements. The brake
drum should be cleaned of rust with emery cloth.

11, CHAIN

It is important to use only good quality chain 5i8" x 1/4" - Regina - CZ - Diamond, etc., and to service

it regularly by washing it in solvent and then lubricating it.

20. Chain Adjustment

21. Master link

Maico 72-74.5 Radial Manaual

bottom and rotated clockwise until it engages and drops into the shock adjustment slots. When the
rod is rotated to the extreme counter-clockwise position, the shock is on the lightest setting.

4. There are five, half-revolution adjustments possible for dampening. We suggest for the first adjust-
ment, 2 to 3 half turns clockwise is ample. This is achieved by rotating the shock rod clockwise while

engaged in the adjustment slots.

5. The shock rod must then be pulled out without rotating it, to release it from the adjustment mecha-

nism.

6. The shock can then be re-assembled in reverse order. Be sure to re-install the rubber bumper. Failing
to do so can seriously damage the shock under use. Pay special attention that the right and left shock

are adjusted equally. This will result in maximum performance of the Koni shocks.

10, WHEELS

The wheels must be centered carefully and exactly. All spokes must be free of damage and adjusted equally
very often. The wheel bearings are checked for play and being sealed from outside elements. The brake
drum should be cleaned of rust with emery cloth.

11, CHAIN

It is important to use only good quality chain 5i8" x 1/4" - Regina - CZ - Diamond, etc., and to service
it regularly by washing it in solvent and then lubricating it.

20. Chain Adjustment

www.maicowerk.com

21. Master link

Courtesy of [e-mail]

B. ASSEMBLY AND REPAIR

INSTRUCTIONS FOR ENGINE

1. Removal from Frame

1.1 Remove the tank

1.2 Remove the exhaust

1.3 Remove the carburetor

1.4 Remove the cylinder head and top engine
brace

1.5 Remove the ignition wire

1.6 Remove the 10 mm x 1 engine mount bolts

front and rear

1.7 Disconnect the chain

1.8 Loosen the 8 mm bolt on bottom of engine

1.9 Remove the clutch cable

1.10 Remove the engine 22. Piston Disassembly

2. Disassembly of Engine

We suggest using the original MAl CO engine stand.

2.1 Drain gear oil - one (SW 17mm) drain plug
on lower left side.

2.2 Remove the cylinder by loosening the four
8 mm nuts (SW 13mm) at the base of the
cyl inder. The paper base gasket is removed
taking care not to tear it. Make sure no dirt
enters the crank case.

2.3 Remove the piston - the circlips on both
sides of the piston are removed with needle
nose pliers. An aluminium pin is used to re-
move the piston pin by tapping the pin
lightly. Use caution not to apply any pres-

sure to the side of the connecting rod.

2.4 Lay engine on primary case side and remove

timing cover.

2.5 Remove stator by loosening and removing 23. Pulling Ignition Magnet
3 - 6 mm screws. Push rubber plug out with

screw driver.

2.6 Remove the 8 mm hex bolt from the center
of the rotor magnet and remove the nut

which keeps the magnet in position on the
crank shaft. A pin, available through your
dealer 60 mm long, is inserted in the middle
of the magnet and the 8 mm bolt is re-inser-
ted and tightened while crank shaft is held
stationary by a wooden fork arou nd the
connecting rod after piston pin is re-inserted,

widging against the wooden fork. The bolt

is tightened until the magnet pops off.

2.7 The engine is turned around with the prima-
ry case facing up. The kickstarter lever is
removed and the 7 case screws. The cover

can then be lifted off.

2.8 Disassembly of the clutch is done with the

help of a two-prong puller. By compressing
the clutch on the clutch push pin with the
puller, the two keeper rings are removed 24. Clutch Disassembly

Maico 72-74.5 Radial Manaual

www.maicowerk.com

Courtesy of [e-mail]

with a screw driver. The puller is then remo-
ved and the clutch plates and springs are lif.
ted out. On the small clutch the clutch nut
retainer is also lifted out. The clutch body
is held stationary with a special tool (avai-
lable through the dealer I while the nut is

loosened and removed. The clutch body,
clutch housing, primary chain, and kickstar.
ter shaft can now be removed.

25. Holding The Clutchbody With
Special Holding Tool

2.9 Removal of the drive sprocket on the
crank shaft - The crank shaft must be

held stationary by the same means as
mentioned before for removal of rotor
magnet.

26. Removing the sprocket on the crankshaft

2.10 Splitting the crank cases - The pull spring of the hook ratchet is removed with pliers after the pull
rod retainer, pull rod, and the eight 6 mm case screws are removed. Light pressure is applied to the

crank shaft journal and main gear shaft.

2.11 Removal of transmission - The shift fork shaft is pulled out, then the main shaft. with slider gears

and eventually the lay shaft. The spacer ring and three needle bearings are then lifted out of the
hole in the final drive gear. The 32 mm nut on the outside of the primary sprocket is removed by
blocking the primary sprocket. The primary sprocket and primary drive gear are then removed by
tapping lightly on it.

2.12 The shift cam and pawl can now be removed.

2.13 The crank shaft can be Iifted out of the right side.

2.14 Removing the bearings requires heating the cases to 120°C (240°FI and a press.

3, Assembly of the engine - Shimming of individual parts

3.1 The installation of the bearings is done by heating the cases to 120°C and a press. Seals must be

coated with locktite on the outer surface and smeared with a grease on the inner surface. Then they
are also installed with a press.

3.2 The right case half is set on the mounting stand.

3.3 The crank shaft is inserted in the right case half.

3.4 The shift cam and pawl with springs are inserted.

with a screw driver. The puller is then remo-
ved and the clutch plates and springs are lif.
ted out. On the small clutch the clutch nut
retainer is also lifted out. The clutch body
is held stationary with a special tool (avai-
lable through the dealer I while the nut is

loosened and removed. The clutch body,
clutch housing, primary chain, and kickstar.
ter shaft can now be removed.

25. Holding The Clutchbody With
Special Holding Tool

2.9 Removal of the drive sprocket on the
crank shaft - The crank shaft must be

held stationary by the same means as
mentioned before for removal of rotor
magnet.

26. Removing the sprocket on the crankshaft

2.10 Splitting the crank cases - The pull spring of the hook ratchet is removed with pliers after the pull
rod retainer, pull rod, and the eight 6 mm case screws are removed. Light pressure is applied to the

crank shaft journal and main gear shaft.

2.11 Removal of transmission - The shift fork shaft is pulled out, then the main shaft. with slider gears

and eventually the lay shaft. The spacer ring and three needle bearings are then lifted out of the

hole in the final drive gear. The 32 mm nut on the outside of the primary sprocket is removed by
blocking the primary sprocket. The primary sprocket and primary drive gear are then removed by

tapping lightly on it.

2.12 The shift cam and pawl can now be removed.

2.13 The crank shaft can be Iifted out of the right side.

2.14 Removing the bearings requires heating the cases to 120°C (240°FI and a press.

3, Assembly of the engine - Shimming of individual parts

3.1 The installation of the bearings is done by heating the cases to 120°C and a press. Seals must be

coated with locktite on the outer surface and smeared with a grease on the inner surface. Then they
are also installed with a press.

3.2 The right case half is set on the mounting stand.

3.3 The crank shaft is inserted in the right case half.

3.4 The shift cam and pawl with springs are inserted.

Maico 72-74.5 Radial Manaual

www.maicowerk.com

Courtesy of [e-mail]

3.5 The final drive gear, spacer ring and three needle bearings, main shaft with sliders, lay shaft with

3.5 The final drive gear, spacer ring and three needle bearings, main shaft with sliders, lay shaft with
sliders, and shift forks are re-fitted. The shift fork shaft can then be re-Iocated.

3.6 A new greased center case gasket is fitted on the caseand the left case half is re-fitted with the eight

6 mm case screws.

3.7 The shimming of the crank shaft and transmission is done with the help of the sketch provided.

27. Shimming the layshaft

28. Shimming the crankshaft

3.8 The transmission is tested in the individual gears to see if the shift forks have sufficient play. If
this is not the case, the problem must be remedied.

3.9 The kickstarter shaft and coil spring are re-inserted and rotated clockwise until there is sufficient
tension. This is usually 1.!..revolutions. The hook ratched and pull rod are re-inserted and the pull
spring re-Iocated on the

2hook ratchet.

3.10 The clutch is inserted next with the main drive sprocket and the primary chain. (Be careful not to

forget the washer between mainshaft bearing and the clutch housing and body). Check to see if
plates are warped or the teeth on the plates are worn. Replace worn out parts.

3.11 Never use more than 20 clutch springs (MC250 - 18 double (0) and MC 400, 440, 501 - large tri-

plex clutch, 20 single ( ) (

l.)

3.12 The primary casecover is re-installed. Be sure the hole in the shift shaft is in line with the pin on

the pull rod.

3.13 The piston is heated lightly and with the help of an aluminium pin, the piston pin is re-installed.
The two piston pin circlips are inserted. Be sure they fit in the grooves completely.

3.14 A basegasket is re-fitted and the cylinder re-mounted.

3.15 The cylinder head is then re-mounted only securing it with the three front bolts, not torquing them
down until the engine is back in the frame, and a softened head gasket is fitted. (This is achieved
by heating the gasket to red-hot and then placing it in cold water!. The head nuts are torqued to

1B foot pounds.

3.16 Gear box is filled with 1 liter gear oil (oil filler screw SW 19).

Maico 72-74.5 Radial Manaual

sliders, and shift forks are re-fitted. The shift fork shaft can then be re-Iocated.

3.6 A new greased center case gasket is fitted on the caseand the left case half is re-fitted with the eight
6 mm case screws.

3.7 The shimming of the crank shaft and transmission is done with the help of the sketch provided.

27. Shimming the layshaft

28. Shimming the crankshaft

3.8 The transmission is tested in the individual gears to see if the shift forks have sufficient play. If
this is not the case, the problem must be remedied.

3.9 The kickstarter shaft and coil spring are re-inserted and rotated clockwise until there is sufficient
tension. This is usually 1.!..revolutions. The hook ratched and pull rod are re-inserted and the pull
spring re-Iocated on the

2hook ratchet.

3.10 The clutch is inserted next with the main drive sprocket and the primary chain. (Be careful not to

forget the washer between mainshaft bearing and the clutch housing and body). Check to see if
plates are warped or the teeth on the plates are worn. Replace worn out parts.

3.11 Never use more than 20 clutch springs (MC250 - 18 double (0) and MC 400, 440, 501 - large tri-

3.12 The primary casecover is re-installed. Be sure the hole in the shift shaft is in line with the pin on

the pull rod.

3.13 The piston is heated lightly and with the help of an aluminium pin, the piston pin is re-installed.
The two piston pin circlips are inserted. Be sure they fit in the grooves completely.

3.14 A basegasket is re-fitted and the cylinder re-mounted.

3.15 The cylinder head is then re-mounted only securing it with the three front bolts, not torquing them
down until the engine is back in the frame, and a softened head gasket is fitted. (This is achieved
by heating the gasket to red-hot and then placing it in cold water!. The head nuts are torqued to

1B foot pounds.

3.16 Gear box is filled with 1 liter gear oil (oil filler screw SW 19).

plex clutch, 20 single ( ) (

l.)

www.maicowerk.com

Courtesy of [e-mail]

C.

ASSEMBLY AND REPAIR INSTRUCTIONS FOR CHASSIS

1. Disassembly of Forks

1.1 Remove front wheel

1.2 Remove handlebars and bar clamps

1.3 Loosen both top 10 mm pinch bolts and remove both fork caps.

1.4 Loosen both bottom pinch bolts and pull both fork tubes out of triple clamps.

1.5 Drain fork oil

1.6 Unscrew bottom fork caps and remove snap rings. Then pull complete dampening units out of the
tubes.

1.7 Pull sliders from fork tubes.

2. Assembly of forks

2.1 The following items must be checked:
The hard chromed surface of the fork tubes, as well as the straightness. The inside surface of the

fork sliders must be without ridges or scratches. The seals must be checked for leakage. Pistons,
valves must be checked for leakage.

2.2 Slide the slider onto the fork tube.

2.3 The complete dampening unit is inserted in the bottom of the fork tube. The snap ring is re-Iocated
and the bottom cap threads are oiled and re-tightened with a 27 mm wrench.

2.4 The fork spring iswell greasedand installed on the fork tube. The rubber fork boots are mounted
over the spring.

2.5 The individual fork tubes are inserted in the triple clamps and the bottom pinch bolts are tightened.

2.6 The top plugs are mounted (making sure the air release valves are functioning properly) and the top
pinch bolts are tightened.

2.7 Handlebars and front wheel are mounted.

3. Swing-Arm - Rear suspension disassembly

3.1 The rear wheel is removed by removing brake rod, chain, and chain guide. The rear axle nut is re-

moved (SW 24mml and then the axle is pulled out

32 The shocks are removed (SW 13mm)

3.3 The swing arm pivot axle nut is removed with SW 19 mm socket

Assembly

3.4 The shocks are tested under use I t is important to have the shock damping adjusted the same.
(Adjustment, see Section IV - 9).

3.5 The swing arm should be checked for straightness and if need be, the swing arm bushings should

be replaced.

3.6 In mounting shocks, caution must be taken not to have any side pressure on them.

4. Disassembly and re-assembly of front wheel

4.1 Remove front brake cable

4.2 Remove 8 mm (SW 13) bolt from brake anchor rod.

4.3 Loosen both 8 mm (SW 13) pinch nuts on the fork sliders.

4.4 Unscrew axle nut (SW 22)and pull

axle by inserting a rod or screwdriver in the hole provided in the

axle.

4.5 The assembly is performed in reverse order.

5. Disassembly and re-assembly of rear wheel

5.1 Remove the master link from chain.

5.2 Remove brake rod.

5.3 Remove chain guide (SW 13) from backing plate.

5.4 Remove rear axle nut with 24 mm wrench. Then pull rear axle

5.5 Remove rear wheel along with brake backing plate.

5.6 The assembly of the rear wheel is performed in reverse order.

C.

ASSEMBLY AND REPAIR INSTRUCTIONS FOR CHASSIS

1. Disassembly of Forks

1.1 Remove front wheel

1.2 Remove handlebars and bar clamps

1.3 Loosen both top 10 mm pinch bolts and remove both fork caps.

1.4 Loosen both bottom pinch bolts and pull both fork tubes out of triple clamps.

1.5 Drain fork oil

1.6 Unscrew bottom fork caps and remove snap rings. Then pull complete dampening units out of the
tubes.

1.7 Pull sliders from fork tubes.

2. Assembly of forks

2.1 The following items must be checked:
The hard chromed surface of the fork tubes, as well as the straightness. The inside surface of the

fork sliders must be without ridges or scratches. The seals must be checked for leakage. Pistons,
valves must be checked for leakage.

2.2 Slide the slider onto the fork tube.

2.3 The complete dampening unit is inserted in the bottom of the fork tube. The snap ring is re-Iocated
and the bottom cap threads are oiled and re-tightened with a 27 mm wrench.

2.4 The fork spring iswell greasedand installed on the fork tube. The rubber fork boots are mounted
over the spring.

2.5 The individual fork tubes are inserted in the triple clamps and the bottom pinch bolts are tightened.

2.6 The top plugs are mounted (making sure the air release valves are functioning properly) and the top
pinch bolts are tightened.

2.7 Handlebars and front wheel are mounted.

3. Swing-Arm - Rear suspension disassembly

3.1 The rear wheel is removed by removing brake rod, chain, and chain guide. The rear axle nut is re-

moved (SW 24mml and then the axle is pulled out

32 The shocks are removed (SW 13mm)

3.3 The swing arm pivot axle nut is removed with SW 19 mm socket

Assembly

3.4 The shocks are tested under use I t is important to have the shock damping adjusted the same.
(Adjustment, see Section IV - 9).

3.5 The swing arm should be checked for straightness and if need be, the swing arm bushings should

be replaced.

3.6 In mounting shocks, caution must be taken not to have any side pressure on them.

4. Disassembly and re-assembly of front wheel

4.1 Remove front brake cable

4.2 Remove 8 mm (SW 13) bolt from brake anchor rod.

4.3 Loosen both 8 mm (SW 13) pinch nuts on the fork sliders.

4.4 Unscrew axle nut (SW 22)and pull

axle by inserting a rod or screwdriver in the hole provided in the

axle.

4.5 The assembly is performed in reverse order.

5. Disassembly and re-assembly of rear wheel

5.1 Remove the master link from chain.

5.2 Remove brake rod.

5.3 Remove chain guide (SW 13) from backing plate.

5.4 Remove rear axle nut with 24 mm wrench. Then pull rear axle

5.5 Remove rear wheel along with brake backing plate.

5.6 The assembly of the rear wheel is performed in reverse order.

Maico 72-74.5 Radial Manaual

www.maicowerk.com

Courtesy of [e-mail]

SHOP BULLETINS

SHOP BULLETINS

AND

RACING MODIFICATIONS

Maico 72-74.5 Radial Manaual

AND

RACING MODIFICATIONS

www.maicowerk.com

Courtesy of [e-mail]

WORK SHOP BULLETIN NO.1

WORK SHOP BULLETIN NO.1

Subj.: 250, 360

&

early

400cc

clutch

If slipping or incomplete clutch release occurs correct as

follows:

1. Steel clutch
Machine .020 inch (.5mm) from the fiber clutch

plate. This machining to be done on one side

only.

2. All fiber clutch
Machine one fiber plate, one side only per

step one above.

Note: USE a total of 20 clutch springs stacked as shown.

(())

(()) (())

(()) (())

Subj.: Late 400

&

501 clutch

If the big clutch will not release, cut the clutch arm (located

on the case) approximately 3/4 inch. Bend the clutch lever out-

ward until the lever fits flat to the bar grip when pulled all

the way in.

If the clutch still will not release, check the splined steel plates

for flatness. If all of the -steel plates are flat, then machine

.010 to .020 from one side of one fiber plate. Be sure to under-

cut the unlined area at least .020 or else the clutch will slip.

Note: USE a total of 18 - 20 clutch springs stacked as shown.

()

()

()

()

() ()

()

()

()

()

Maico 72-74.5 Radial Manaual

Subj.: 250, 360

&

early

400cc

clutch

If slipping or incomplete clutch release occurs correct as

follows:

1. Steel clutch
Machine .020 inch (.5mm) from the fiber clutch

plate. This machining to be done on one side

only.

2. All fiber clutch
Machine one fiber plate, one side only per

step one above.

Note: USE a total of 20 clutch springs stacked as shown.

(())

(()) (())

(()) (())

Subj.: Late 400

&

501 clutch

If the big clutch will not release, cut the clutch arm (located
on the case) approximately 3/4 inch. Bend the clutch lever out-
ward until the lever fits flat to the bar grip when pulled all

the way in.

If the clutch still will not release, check the splined steel plates

for flatness. If all of the -steel plates are flat, then machine

.010 to .020 from one side of one fiber plate. Be sure to under-

cut the unlined area at least .020 or else the clutch will slip.

Note: USE a total of 18 - 20 clutch springs stacked as shown.

()

()

()

()

() ()

()

()

()

()

www.maicowerk.com

Courtesy of [e-mail]

SHOP BULLETIN #3

SHOP BULLETIN #3

t50LLf. TIN

Z50C-L .

/0'OOlf/l:./I T7LJ!J5

Z3m,

2 I

If!

tfl

STO

,__ 5'MM

I

I"

AIM

-

:5TA6F I

FOE MDlDCeLJ55 ~

TPAIL !CID/Nt:.,

E X/lIlOJT

POET

I~Mtv1

/I.JLFT

4

800)

T ?OIZ T

MAIt[ E

'fHIlOSr POET ~' /NtET

'pOe.T

//5

WIDF AS PlJfSII3Li?

IUI.TUf

THE STUO

HOfEJ

THfiY

ARE

VEeY

Liar:

TV

7JI{"

RJ.e:T5,

DD

Nor EmS£" De LDwm )'NV DF 7JlF

PlJI!JS.

MATUlIiCU 1)1

P!S7l)1J

TO l!i2ZTflYZT

5TAb[

J[

FOIZ

F/lfT

AfOlJLPLXJ ['

TT

.!L£I#un

7Jl1J/5PLfJ5

smt£

r

LilT

FYI/110fT I-IEA'O

R/l?

3.5

/1IU1t0. M[){j~LLW.1l

FOI?RJJAf!..DtT

UJtR.D.

ADD I.ZS-

INUf£S

TV

L£JJTR:

¥07DI.J

Ll:AJi.Tl-f.

fAlSE EXf./AtJIT POIZT HElI::.f.!T TO

36

Mill.

USE 34MM C/lR..15

oe:

st:,NN{jli!K

5T1/6FIlL

IT

5Le"UIt'&S ~ eDAD

1Z.40AJ6

t:"iC..

THIS 1\

HA&£ I ~ II 'WlJ~_

MIU H£A.D

D.050

/I.JUI£5.

LUT.

050

FEDM QU£}Jt..N AffA

DO

NOT L..HIl1J6e

7JlF LLJ.NT!JtJ~.

KETfI~ /6N/TlOJJ To

/.5

MM 13TDt....

1Z1J/5£""'

£VlAtJ5T

POET TV

.Sk

MM

l[,wnOIJ

MUST

M

MOD I FlED

ID

NUJTr

MAffi 125

PDIIJTS Oe.

MISSFI~

WILL

OLLof!.- .

t.DW~r... I~LET

ra

113

IJM

mE. [/-lAMP(Of\l

L:-li:. O~

Bl)'SLH 340

PillL:.

'S.

Maico 72-74.5 Radial Manaual

Z50C-L .

:5TA6F I

-

E X/lIlOJT

MAIt[ E

IUI.TUf

Nor EmS£" De LDwm )'NV DF 7JlF

5TAb[

'fHIlOSr POET ~' /NtET

THE STUO

J[

t50LLf. TIN

/0'OOlf/l:./I T7LJ!J5

FOE MDlDCeLJ55 ~

,__ 5'MM

I

POET

HOfEJ

FOIZ

F/lfT

I"

THfiY

AfOlJLPLXJ ['

AIM

'pOe.T

ARE

VEeY

PlJI!JS.

TT

TPAIL !CID/Nt:.,

I~Mtv1

/I.JLFT

//5

Liar:

MATUlIiCU 1)1

.!L£I#un

4

800)

WIDF AS PlJfSII3Li?

TV

T ?OIZ T

7JI{"

P!S7l)1J

7Jl1J/5PLfJ5

RJ.e:T5,

TO l!i2ZTflYZT

smt£

DD

2 I

STO

r

Z3m,

If!

tfl

LilT

ADD I.ZS-

fAlSE EXf./AtJIT POIZT HElI::.f.!T TO

USE 34MM C/lR..15

5T1/6FIlL

MIU H£A.D

DO

KETfI~ /6N/TlOJJ To

1Z1J/5£""'

l[,wnOIJ

MISSFI~

mE. [/-lAMP(Of\l

FYI/110fT I-IEA'O

INUf£S

NOT L..HIl1J6e

£VlAtJ5T

THIS 1\

D.050

MUST

WILL

t.DW~r... I~LET

IT

M

R/l?

TV

3.5

L£JJTR:

oe:

5Le"UIt'&S ~ eDAD

7JlF LLJ.NT!JtJ~.

POET TV

MOD I FlED

OLLof!.- .

ra

L:-li:. O~

HA&£ I ~ II 'WlJ~_

/I.JUI£5.

113

IJM

/1IU1t0. M[){j~LLW.1l

st:,NN{jli!K

ID

¥07DI.J

36

LUT.

/.5

MM 13TDt....

.Sk

NUJTr

Bl)'SLH 340

Ll:AJi.Tl-f.

Mill.

1Z.40AJ6

050

MM

MAffi 125

FEDM QU£}Jt..N AffA

FOI?RJJAf!..DtT

t:"iC..

PDIIJTS Oe.

PillL:.

'S.

UJtR.D.

www.maicowerk.com

Courtesy of [e-mail]

SHOP BULLETIN

Maico 72-74.5 Radial Manaual

#9

If the ~ear box is missing gears either shifting up or

shifting down, this means that the shift linkage is not in

its center location.

To position the shift linka~e into its proper location,

remove the

clutch cover

and push the shift linkage pull rod
No. 1750 forward to its maxlum travel. Mark this position of
the pin in the rod onto the

cil.

Now pull the rod all the way to the rear and mark this

case

position of the pull rod pin onto the

gasket

case

surface;

use a pen-

gasket surface.

Now divide the distance between these two marks. Mark
this center position line over the gasket surface and con-
tinue the line 1/2 inch out over the outside of the case.

Next mark tne center line of the shift shaft pin hole

(No. 1049). Draw this line over the gasket surface and con-

tinue this line onto the outer surface of the

place the cover onto the

case.

case.

Now

If the two lines are not matched, then remove the shift

spindle from the

case

lines match. Replace the spindle into the

the

center

line of the shift spindle pin hole. Reinstall the

and bend the dog leg portion until the

cover

and remark

cover onto the case and re-examine the marks. Adjust the shift

spindle once again

if

necessary.

www.maicowerk.com

Courtesy of [e-mail]

SHOP BULLETIN #11

SHOP BULLETIN #11

T T pipe for 400cc may be made by

cutting the center cylinderical section
of the exhause pipe 2.75 inches.
Widen all ports to maximum. Do not

raise or lower ports.

CAUTION:

This raises the RPM.

Reduces low speed torque.

Reduces reliability.

Increases speed " horsepower.

This is not for motocross.

Maico 72-74.5 Radial Manaual

T T pipe for 400cc may be made by

cutting the center cylinderical section
of the exhause pipe 2.75 inches.
Widen all ports to maximum. Do not

raise or lower ports.

CAUTION:

This raises the RPM.

Reduces low speed torque.

Reduces reliability.

Increases speed " horsepower.

This is not for motocross.

www.maicowerk.com

Courtesy of [e-mail]

SERVICE BULLETIN

SERVICE BULLETIN

Inepection and AdJuetment of the 250, 400, 450, and 501 Tranemieeion

Before taking the engine apart it ie recommended to clean the engine.

Try to avoid direct steel hammer hits on the parts. Split the engine carefully

and take out the tranemiseion.

Check for wear: dog pinion gear, sliding geare, shifting forks,

cam assembly, guide bush.

Check for excess eide play: between retainer ring and dog pinion

gear.

ATTENTION: Brakeage of transmiseions can be caused by improper chain alignment.

(Chain jumps out of sprocket and locks the engine.)

On 250, 400, 501 Square barrel 'T' or old tranemisslons check the mainshaft or

bronte bush and sleeve pinion for free rotation. Before assembling or in.erting

into the counterehaft it ehou1d be lubricated with anti-friction 1ub.

Cleaning the tranemiesion parts and gears is advisable for proper adjuetment ••

1. Ineert the geare and with crankcaee gasket close the engine houeings. The

layshaft clearance should be checked after fixing the engine ca.e. together

and tightened with three middle engine screws. The engine ca.es are ea.y to

work without the crankehaft. Tighten the countershaft nut. The inspection

of the tranemission gears is easier to check with the engine case. lying

clutch side up.

2. Leave the gear engaged in nautra1 poeition and fix the dial indicator (.hovn

in fig. #2) on the caee. With the half of a bended hook the end .hould be

inaerted into the hole (fig. #2B), lifting the third gear in the 1ayshaft

find the L/Shaft clearance. The layshaft clearance should be 0.10

DID

(.004")

to 0.20

DID

(.008"). If it 1a lI'Drethan that, ehims ehou1d be added to

obtain the clearance.

Maico 72-74.5 Radial Manaual

Inepection and AdJuetment of the 250, 400, 450, and 501 Tranemieeion

Before taking the engine apart it ie recommended to clean the engine.

Try to avoid direct steel hammer hits on the parts. Split the engine carefully

and take out the tranemiseion.

Check for wear: dog pinion gear, sliding geare, shifting forks,

cam assembly, guide bush.

Check for excess eide play: between retainer ring and dog pinion

gear.

ATTENTION: Brakeage of transmiseions can be caused by improper chain alignment.

(Chain jumps out of sprocket and locks the engine.)

On 250, 400, 501 Square barrel 'T' or old tranemisslons check the mainshaft or

bronte bush and sleeve pinion for free rotation. Before assembling or in.erting

into the counterehaft it ehou1d be lubricated with anti-friction 1ub.

Cleaning the tranemiesion parts and gears is advisable for proper adjuetment ••

1. Ineert the geare and with crankcaee gasket close the engine houeings. The

layshaft clearance should be checked after fixing the engine ca.e. together

and tightened with three middle engine screws. The engine ca.es are ea.y to

work without the crankehaft. Tighten the countershaft nut. The inspection

of the tranemission gears is easier to check with the engine case. lying

clutch side up.

2. Leave the gear engaged in nautra1 poeition and fix the dial indicator (.hovn

in fig. #2) on the caee. With the half of a bended hook the end .hould be

inaerted into the hole (fig. #2B), lifting the third gear in the 1ayshaft

find the L/Shaft clearance. The layshaft clearance should be 0.10

to 0.20

DID

(.008"). If it 1a lI'Drethan that, ehims ehou1d be added to

obtain the clearance.

DID

(.004")

www.maicowerk.com

Courtesy of [e-mail]

3. Insert the thrust washer in the mainshaft, either by inserting the

3. Insert the thrust washer in the mainshaft, either by inserting the

clutch body, or use some bushes to pull the mainshaft all the way towards

clutch side and tighten the !Minshaft. nut. With a screwdriver turn the cam

into the neutral position. Shifting forI:. should be inspected through t.he

hole (fig. #2

A,

B) for up and down axle play.

4. Turn the cern to the first gear posit.ion and insert. the hooked "ire in hole

E (fig.

t(2)

and lift up the aecond gear Oay.haft. slider). Check the upper

shift fork axle play through the hole A.

5. l".ave the shiftinB

C~r-I

into the second gear position and hook the "ire into

the hole A (fig. 112) and the third Bear in the mainshaft should be lifted

(mainshaft slider) upwards. (You miBht not be able to find the play if you

did not pull the main9haft to"ards clutch 9ide.) Check the bottom fork play.

6. The cam is shifted to tlle third gear position and the hool:ed wire should be

inserted into the hole B (fig.

n)

and pre99 down the layshaft slider and

check the upper for!: play.

7. For fourth gear groove the gear into the fourth Bear position and ingert the

\lire in hole

t.

(fig.

;IL).

The third gear

b

the main shaft. (Mains:,aft

sliding gear) should be pressed down ,.,hile checking the bottom fork play.

For the radial crankshafts tl:e play should be cI,ecleed, if you changed the cranle,

main bearings and crankcaae:i .. :.Jith the

heIr

of

B

feeler gauge insert the feeler

gauge in between tlle crank and ~ngine cases. The cranlecase play should be

0.20"""

(.OOC") to 0.36 rrrn (0.11:"). If it i9 rrore than that, shims should be

obtained until clearance i. obtained.

Some of the reason9 for gear slipping:

The hooked rachet shou Id be inspect.ed in \,oth edges (f ig.

I!3C).

Check the pu 11rod

for bend. To avoid the over engagement "eld the hool:ed rechet as shown in

fig.

'3

B. to "btain the clearance in the C'IBes. Fig.

n

A OIl to 112

1ml)(1••

13").

There la a difference in the gear changing crank (shiftershaft) and the gear

changing pullrod between Radials (~50, 1:00, 1:50, SOl, V, Vl) and the S"uare

Barre19. The gear change return apring must be bent and adjusted so that the

gearchanging cran!: shifts in proper \lay, in accordance with the modification

to the pullrod and the crankcase (fig.

J~

area9 A&.C). The proper position

for the crank adju9ted "ith the 9ide cover scre\l hole as shown in fig.

1ft,.

S.

Illustration Fig.

ill: "

depicts the related positions for the 250,

1;00,

and 1.50

Maico 72-74.5 Radial Manaual

clutch body, or use some bushes to pull the mainshaft all the way towards

clutch side and tighten the !Minshaft. nut. With a screwdriver turn the cam

4. Turn the cern to the first gear posit.ion and insert. the hooked "ire in hole

into the neutral position. Shifting forI:. should be inspected through t.he

hole (fig. #2

E (fig.

t(2)

A,

B) for up and down axle play.

and lift up the aecond gear Oay.haft. slider). Check the upper

shift fork axle play through the hole A.

5. l".ave the shiftinB

C~r-I

into the second gear position and hook the "ire into

the hole A (fig. 112) and the third Bear in the mainshaft should be lifted

6. The cam is shifted to tlle third gear position and the hool:ed wire should be

7. For fourth gear groove the gear into the fourth Bear position and ingert the

(mainshaft slider) upwards. (You miBht not be able to find the play if you

did not pull the main9haft to"ards clutch 9ide.) Check the bottom fork play.

inserted into the hole B (fig.

n)

and pre99 down the layshaft slider and

check the upper for!: play.

\lire in hole

t.

(fig.

;IL).

The third gear

b

the main shaft. (Mains:,aft

sliding gear) should be pressed down ,.,hile checking the bottom fork play.

For the radial crankshafts tl:e play should be cI,ecleed, if you changed the cranle,

main bearings and crankcaae:i .. :.Jith the

heIr

of

B

feeler gauge insert the feeler

gauge in between tlle crank and ~ngine cases. The cranlecase play should be

0.20"""

obtained until clearance i. obtained.

(.OOC") to 0.36 rrrn (0.11:"). If it i9 rrore than that, shims should be

Some of the reason9 for gear slipping:

The hooked rachet shou Id be inspect.ed in \,oth edges (f ig.

I!3C).

Check the pu 11rod

for bend. To avoid the over engagement "eld the hool:ed rechet as shown in

fig.

There la a difference in the gear changing crank (shiftershaft) and the gear

changing pullrod between Radials (~50, 1:00, 1:50, SOl, V, Vl) and the S"uare

Barre19. The gear change return apring must be bent and adjusted so that the

gearchanging cran!: shifts in proper \lay, in accordance with the modification

to the pullrod and the crankcase (fig.

for the crank adju9ted "ith the 9ide cover scre\l hole as shown in fig.

Illustration Fig.

'3

B. to "btain the clearance in the C'IBes. Fig.

J~

area9 A&.C). The proper position

ill: "

depicts the related positions for the 250,

n

A OIl to 112

1;00,

1ml)(1••

1ft,.

S.

and 1.50

13").

www.maicowerk.com

Courtesy of [e-mail]

radial. and also the U 501. The fig.

radial. and also the U 501. The fig.

ff0

C depicts the related positions for

th~ 250, 360, ~OO .~d 501 sq~are barrels.

The crank return spring in Fig. 94 B must apply pressure to both sides of the

positioning stub (fig. 94 areas D-l and D-2) and no clearance should be present.

Service Bulletin No.1
February

n,

197~

Maico 72-74.5 Radial Manaual

th~ 250, 360, ~OO .~d 501 sq~are barrels.

The crank return spring in Fig. 94 B must apply pressure to both sides of the

positioning stub (fig. 94 areas D-l and D-2) and no clearance should be present.

Service Bulletin No.1

n,

February

197~

ff0

C depicts the related positions for

www.maicowerk.com

Courtesy of [e-mail]

)

(

~ri,,~

fT~

I~

o

5HIM

C

I~,

b'.__ "' .

M

,

."

i

J

~1

:

..

'

-~'I

, Is

L

.,,""

~ __ f

~t:!".l'{,.

! -,

I~l~

I

l

~ndQea" :

.- " -..l

I

e

f--__

3--':~~a;_~

I

i

LAY

SHAH

@

'''-:.~

,

.

,

\

FIGW~E NO:

1

.j

I

.

,.--./

.~,/"

/

..

e~II=T FOR'tC ~6NC CHECI<\N<;"

'I'; I

HAIN SHArT

tV

L.aYlOhQH

pla.y

O.ZOm.,.,

0.008 inc.l1

(Ij Chec k

+h4l

6hif+ forM. PLo.~

~-~

+'"

Gt

eo"

"----

~

Wi----lR

TRANSMISl)ION

DATE :

g

III

Jan

19~4

DE5/GNfiD :

SEI¥AIM1 •••••

nl:c,~1\oJ •.•

1"'\.

J "'.

Maico 72-74.5 Radial Manaual

~t:!".l'{,.

.,,""

L

, Is

~ __ f

19~4

Jan

III

~ri,,~

i

J

o

-~'I

I~

fT~

5HIM

:

'

~1

..

! -,

I

i

."

b'.__ "' .

I~,

C

,

M

I

I

.- " -..l

~ndQea" :

I~l~

Wi----lR

g

DATE :

TRANSMISl)ION

J "'.

SEI¥AIM1 •••••

1"'\.

nl:c,~1\oJ •.•

DE5/GNfiD :

~

"----

l

3--':~~a;_~

f--__

(

1

)

FIGW~E NO:

@

SHAH

LAY

\

,

.

,

'''-:.~

I

.j

.~,/"

,.--./

.

..

/

e

e~II=T FOR'tC ~6NC CHECI<\N<;"

'I'; I

HAIN SHArT

eo"

Gt

~-~

+'"

0.008 inc.l1

O.ZOm.,.,

6hif+ forM. PLo.~

pla.y

+h4l

L.aYlOhQH

tV

(Ij Chec k

www.maicowerk.com

Courtesy of [e-mail]

I

..

o

,

u)

cr

:>

~

u.

"\

~.

o

l-

to.

<

:t

<J)

>-

j

o

.•..

~

•••

c>

0

C

2

III

"

i

t-

...,

~

•••

4

•••

r

:A

..J

a>

u

lei

(IJ

~

-<

U

~

~

ILl

"

-

~

I-

~

<t

'U

Q

I

..

o

,

u)

cr

:>

~

u.

"\

~.

o

l-

to.

<

:t

<J)

>-

j

o

.•..

~

•••

c>

0

C

2

III

"

i

t-

...,

~

•••

4

•••

r

:A

..J

a>

u

lei

(IJ

~

-<

U

~

~

ILl

"

-

~

I-

~

<t

'U

Q

Maico 72-74.5 Radial Manaual

www.maicowerk.com

Courtesy of [e-mail]

.

----:

.

<:t

•••••

Ot

2:

Ii

ri

~

t1

H

•••

£

~

<

lU

~

~

CI

•••

:I:

CD

U

..

"l."

0

a:-

D

2:

Q

...,

2:

z

w

~

~ ~

••

-

'"

0

t-

el)

~

0

<

•••

:I:

a

0

,

,.

,

,

..'

u

----:

-

/

.----

/

I

\cn

-

~l

a

z

Maico 72-74.5 Radial Manaual

-

.----

/

<:t

•••••

Ot

2:

ri

Ii

H

~

•••

u

/

Q

w

~ ~

0

0

:I:

lU

:I:

U

"l."

a:-

£

CI

••

t-

<

a

~

~

•••

CD

D

...,

2:

-

el)

•••

0

t1

<

~

..

0

2:

z

~

'"

~

,

..'

,

,.

,

I

\cn

-

~l

a

z

www.maicowerk.com

Courtesy of [e-mail]

RADIAL.

Jon19H.

FIGURE

NO:

4-

~o.

"00.

new

501

RADIAL.

c

-----

--.......-- .. -._~ - E

G.E.AR

CfjANGINGCRMJK

OATE :

91M

Jon19H.

DESIGNED

:SILVARAJ.N.

Of.'

5IC'N

Nn' /. ~ ,

.250.4-00,

so,

SC,fUARE

BARREL

"~

0,

F

o.

A

Maico 72-74.5 Radial Manaual

91M

:SILVARAJ.N.

Nn' /. ~ ,

so,

BARREL

c

CfjANGINGCRMJK

OATE :

G.E.AR

5IC'N

Of.'

DESIGNED

.250.4-00,

SC,fUARE

--.......-- .. -._~ - E

"~

F

0,

-----

4-

501

NO:

new

www.maicowerk.com

FIGURE

"00.

~o.

A

o.

Courtesy of [e-mail]

ShU> dULLE11~ ,.

ShU> dULLE11~ ,.

4UOcc

Cooper Motors aoes not recommend Increasing tne "Vuce

engine speed through changing the ports or changing the

exhdUS'

system. Some performance can be gained by widening the Inlet
and exhaust ports as described Stage

I.

of the 250cc bulletin.
For TT performance remove 2.75 inches from the center
cylinderical section of the expansion chamber and reweld. The

main pipe mount will have to be moved the same amount.

SHOP BULLETIN #5

Rear Sprocket Bolts

We suggest that the rear sprocket bolts be secured using
Loc-tite Stud lock grade and then tightened to 10 foot pounds.
Tighten the lock nuts to 10 foot pounds also. Allow 24 hours
for the Loc-tite to harden.

SHOP BULLETIN #6

Rear Wheel S~okes

It is suggested to

~IShSSem~l~ tn.

re.r wheel flange side
spokes and install flat washers under tr,espoke heads. This
keeps the spokes from bending the flange and coming loose.-

SHOP EULLETIN #7

Rear Wheel Bearings

Metal chips left in the rear hub during fabrication will

fallout of the vent holes and cause the rear wheel bearings

to seize. It is suggested to cover over the two vent holes,

located between the wheel bearings. with duct tape.

SHOP BULLETIN #8

Leaking Forks

The front forks will
on top of the fork seal.
on top of the new seal to

leak if dirt is allowed to accumulate
It is suggested to use an old fork
prevent dirt from damaging the new seal.

Maico 72-74.5 Radial Manaual

4UOcc

Cooper Motors aoes not recommend Increasing tne "Vuce
engine speed through changing the ports or changing the
system. Some performance can be gained by widening the Inlet

I.

and exhaust ports as described Stage

of the 250cc bulletin.
For TT performance remove 2.75 inches from the center
cylinderical section of the expansion chamber and reweld. The

main pipe mount will have to be moved the same amount.

SHOP BULLETIN #5

Rear Sprocket Bolts

We suggest that the rear sprocket bolts be secured using
Loc-tite Stud lock grade and then tightened to 10 foot pounds.
Tighten the lock nuts to 10 foot pounds also. Allow 24 hours
for the Loc-tite to harden.

SHOP BULLETIN #6

exhdUS'

Rear Wheel S~okes

It is suggested to

spokes and install flat washers under tr,espoke heads. This

~IShSSem~l~ tn.

re.r wheel flange side

keeps the spokes from bending the flange and coming loose.-

SHOP EULLETIN #7

Rear Wheel Bearings

Metal chips left in the rear hub during fabrication will

fallout of the vent holes and cause the rear wheel bearings

to seize. It is suggested to cover over the two vent holes,

located between the wheel bearings. with duct tape.

SHOP BULLETIN #8

Leaking Forks

The front forks will

on top of the fork seal.

on top of the new seal to

leak if dirt is allowed to accumulate
It is suggested to use an old fork

prevent dirt from damaging the new seal.

www.maicowerk.com

Courtesy of [e-mail]

,

)

---._

..

----_._--

":::::,L\OL\C MDD\t="\UT\D~\

I. WELD 1'''-l...B NUT OWr=r TLY O'JEf:':_ ,HE

"0

If

I I\.l

~L:.~.

D~\LLlt_lt::O\..)GH

l\-\E

HOLE

IN Tf-Ir=:

NUT

WITH A.

3/'10

DE:.1U-.

~'1 TO KGEP

,~1E"

c.~

IP';. ~M 1==l:>..LL

11\

\t...

INTO

Tl-1

E ~

14DC...1C..

z.

~PeJNl..~ ....

C1{\ ITlED

~~'(l

u.A~11Y

.3 . C£A.I N "'T\-\

e:

0 IL I~

TO ().. MEA

c,lJ

f'::.1

tUb CD

Po"

TI4EF=F ~\-\Ol..'.L.D

l'O"E.

~ClT \ Y'L

OLJN(£~.

4. MI X.

~/1

0I:l/-JLE

Of: AU1DMIHlc...

~::'M'''~/ON

F="l..J.j'D

"""il:J

~I

if

DO

NLE

D ~ 2Cl

wr

MD1De:....

0 IL .

5. F\LL

U~\NL.

t...

c...LS,

3.

'N \

DIL C~N

t::.:s. ~

I=LlN N

El_ •

~\E::.DK.E

It-I

e:-

"S H D L \

c...

'S..

u

l:::.

1=""\ D P

:a

C:D '-N N

U NTI L \

'/"L

OQ~c...E"::.OF

I="LU

ID H~

"FIt I

F

D \~TO

TI-IE.

D

"-IIT

&, .

11 (,

w

n:::-

N

--n...\

E:

mL:T

:::.0

n-J

t,."T

&:::L.•

I--lEl:::.D

\"Dl.~L..\-IC=~

\l-Il::::

l'llJT r-I

\C..ML'Y.

o

\.

/

\JIEiL.Cl

"lLJr

HEEE

("E

BOT NaT

ITbl-rTF-..NE D

W8J)

Qt

r:£.A7E

,

L __..

,

)

---._

..

----_._--

":::::,L\OL\C MDD\t="\UT\D~\

I. WELD 1'''-l...B NUT OWr=r TLY O'JEf:':_ ,HE

"0

If

I I\.l

~L:.~.

D~\LLlt_lt::O\..)GH

l\-\E

HOLE

IN Tf-Ir=:

NUT

WITH A.

3/'10

DE:.1U-.

~'1 TO KGEP

,~1E"

c.~

IP';. ~M 1==l:>..LL

11\

\t...

INTO

Tl-1

E ~

14DC...1C..

z.

~PeJNl..~ ....

C1{\ ITlED

~~'(l

u.A~11Y

.3 . C£A.I N "'T\-\

e:

0 IL I~

TO ().. MEA

c,lJ

f'::.1

tUb CD

Po"

TI4EF=F ~\-\Ol..'.L.D

l'O"E.

~ClT \ Y'L

OLJN(£~.

4. MI X.

~/1

0I:l/-JLE

Of: AU1DMIHlc...

~::'M'''~/ON

F="l..J.j'D

"""il:J

~I

if

DO

NLE

D ~ 2Cl

wr

MD1De:....

0 IL .

5. F\LL

U~\NL.

t...

c...LS,

3.

'N \

DIL C~N

t::.:s. ~

I=LlN N

El_ •

~\E::.DK.E

It-I

e:-

"S H D L \

c...

'S..

u

l:::.

1=""\ D P

:a

C:D '-N N

U NTI L \

'/"L

OQ~c...E"::.OF

I="LU

ID H~

"FIt I

F

D \~TO

TI-IE.

D

"-IIT

&, .

11 (,

w

n:::-

N

--n...\

E:

mL:T

:::.0

n-J

t,."T

&:::L.•

I--lEl:::.D

\"Dl.~L..\-IC=~

\l-Il::::

l'llJT r-I

\C..ML'Y.

o

\.

/

\JIEiL.Cl

"lLJr

HEEE

("E

BOT NaT

ITbl-rTF-..NE D

W8J)

Qt

r:£.A7E

,

L __..

Maico 72-74.5 Radial Manaual

www.maicowerk.com

Courtesy of [e-mail]

SHOP BULLETIN #2

400cc

400CC

400cc

400cc

501cc

250cc

250cc

250cc

I

4

1

6DP

1

1

0

6DH

6fJ

Needle

Needle-Kotches from

2

2

2

2

2

2

5

3

lean oosition

159

159

159

1610

275-280

0-5

285- 290

280-285

109

p-o

1)-5

Needle Jet

--

5

1

2.5

1

1

3.0

2.0

1,5

Slide

-----

35

40

35

35

40

20

35

35

Pilot Jet

I

,

-

-

2.0

-

-

-

2.0

2.0

Po

ir Jet

i

1,5

I

1,5

1,5

1,5

1,5

1,5

1,5

2.0

1 1/2

Air Screw (Turns)

'-

165

170-180

210

180-190

17 5-18 5

I

420

270

310

Main Jet

Engine Timing

3.0

2.7

2.7

3.5

3.8

3.8

3.8

__ ,_,l-,~

BTDC (mm)

----"----

----------_.

30

36

34

36

36

I

36

34

36

Carburettor (mm)

Binz

Bin~

,

Mikuni

BinR

Bin:7

!

Amal

Mikuni

Mikuni

Size and Make

Champion spark

L-2G

L-2G

L-2G

N-2G

L-2G

L-2G

L-2G

L-2G

nlup-. GAP at

.022-.024

L-3

L-3G

L-3G

-

-

i

-

-

-

Hot Plug

I

This jetting was developed using a Zollner engine dynomometer at C.R. Axtell's in Glendale,

Calif. The jetting is for maximum horse power Sea level to about 3500 feet. If jetting

changes are required always chanp,e the pilot jet first, then the needle jet, then slide, then

the main jet.

for a rouf.h rule of thumb reduce the jet sizes 10% for every 5000 feet of altitude ie 40 pilot

to 35 then to

30.

NOTE: The Bing Carburettor is usuallv supplied one needle jet too rich.

Carburettor-Jettin~ for sea level

SHOP BULLETIN #2

400cc

400CC

400cc

400cc

501cc

250cc

250cc

250cc

I

4

1

6DP

1

1

0

6DH

6fJ

Needle

Needle-Kotches from

2

2

2

2

2

2

5

3

lean oosition

159

159

159

1610

275-280

0-5

285- 290

280-285

109

p-o

1)-5

Needle Jet

--

5

1

2.5

1

1

3.0

2.0

1,5

Slide

-----

35

40

35

35

40

20

35

35

Pilot Jet

I

,

-

-

2.0

-

-

-

2.0

2.0

Po

ir Jet

i

1,5

I

1,5

1,5

1,5

1,5

1,5

1,5

2.0

1 1/2

Air Screw (Turns)

'-

165

170-180

210

180-190

17 5-18 5

I

420

270

310

Main Jet

Engine Timing

3.0

2.7

2.7

3.5

3.8

3.8

3.8

__ ,_,l-,~

BTDC (mm)

----"----

----------_.

30

36

34

36

36

I

36

34

36

Carburettor (mm)

Binz

Bin~

,

Mikuni

BinR

Bin:7

!

Amal

Mikuni

Mikuni

Size and Make

Champion spark

L-2G

L-2G

L-2G

N-2G

L-2G

L-2G

L-2G

L-2G

nlup-. GAP at

.022-.024

L-3

L-3G

L-3G

-

-

i

-

-

-

Hot Plug

I

This jetting was developed using a Zollner engine dynomometer at C.R. Axtell's in Glendale,

Calif. The jetting is for maximum horse power Sea level to about 3500 feet. If jetting

changes are required always chanp,e the pilot jet first, then the needle jet, then slide, then

the main jet.

for a rouf.h rule of thumb reduce the jet sizes 10% for every 5000 feet of altitude ie 40 pilot

to 35 then to

30.

NOTE: The Bing Carburettor is usuallv supplied one needle jet too rich.

Carburettor-Jettin~ for sea level

Maico 72-74.5 Radial Manaual

www.maicowerk.com

Courtesy of [e-mail]