Robin EH72 Service Manual

SERVICE
MANUAL

Model

EH72
ENGINES

PUB-ES1545
Rev. 09/03

940 Lively Blvd. • Wood Dale, IL 60191 • Phone: [phone] • Fax: [phone]

e-mail: [e-mail] • www.robinamerica.com

© Copyright 2003 Robin America, Inc.

CONTENTS

Section Title Page

1. SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2. PERFORMANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3. FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4. GENERAL DESCRIPTION OF ENGINE COMPONENTS . . . . . . . . . . . . . . . . . . . . 5

5. DISASSEMBLY AND REASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

5-1 PREPARATIONS AND SUGGESTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

5-2 SPECIAL TOOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

5-3 DISASSEMBLY PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5-4 REASSEMBLY PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

5-5 BREAK-IN OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

6. MAGNETO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

7. LUBRICATION SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

8. CARBURETOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

9. ELECTRIC STARTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

10. TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

10-1 NO ENGINE OPERATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

10-2 STARTING DIFFICULTIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

10-3 INSUFFICIENT OUTPUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

10-4 OVERHEAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

10-5 ROUGH IDLING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

10-6 HIGH ENGINE OIL CONSUMPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

10-7 HIGH FUEL CONSUMPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

10-8 DETONATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

10-9 ENGINE MISFIRE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

11. INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

12. SERVICE DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

12-1 STANDARD DIMENSIONS AND SERVICE LIMITS . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

12-2 TIGHTENING TORQUE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

12-3 OIL GRADE CHART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

13. MAINTENANCE AND STORAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

13-1 DAILY MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

13-2 PERIODIC MAINTENANCE SCHEDULE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

13-3 ENGINE STORAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

– 1 –

1. SPECIFICATIONS

Model EH72D

Type

Air-Cooled, 4-Stroke, V-Twin Cylinder,

Horizontal P.T.O. shaft, OHV Gasoline Engine
Bore×stroke mm (in.) 2 - 84 x 65 (3.31 x 2.56)
Displacement cm3(cu. in.) 720 (43.9)
Compression Ratio 8.1
Continuous Output kW (HP) / r.p.m. 13.4 (18.0) / 3600
Maximum Output kW (HP) / r.p.m. 18.6 (25.0) / 3600

Maximum Torque N•m / r.p.m.

(kgf•m / r.p.m.)
(ft•lb. / r.p.m.)

53.6 / 2500

(5.5 / 2500)

(39.78 / 2500)

Direction of Rotation Counterclockwise as viewed from P.T.O. shaft side
Cooling System Forced Air Cooling
Valve Arrangements Overhead Valve (OHV)
Lubrication Full pressure type with oil Cooler

Lubricant Automotive Engine Oil SAE #20, #30 or 10W-30; Class SE or higher
Capacity of Lubricant L (U.S. gal.) 1.55 (0.41)

Carburetor Down Draft, Float Type (With Accel Pump)
Fuel Automotive Unleaded Gasoline
Fuel Feed System Diaphragm Pump (Pulse type)
Ignition System Flywheel Magneto (Solid State)
Spark Plug NGK-BPR6ES
Charging Capacity V - A 12 - 15 or 12 - 30
Starting System Electric Starter
Governor System Centrifugal Flyweight Type
Air Cleaner Double Element Type
Dry Weight kg (lb.) 46 (101.3)
Dimension (L×W×H)

mm (in.)

317 × 477 × 475 (12.5 × 18.8 × 18.7)

＊ Specifications are subject to change without notice.

– 2 –

2. PERFORMANCE

2-1 MAXIMUM OUTPUT

The maximum output is the output of an engine with its throttle valve fully opened under the condition that all
the moving parts are properly worn in after the initial break-in period.
A new engine may not produce full maximum output while its moving parts are still not broken-in.

NOTE :
Power curves shown in the following charts are made in conformity to SAE internal combustion engine
standard test code J1349

2-2 CONTINUOUS RATED OUTPUT

The continuous rated output is the output of an engine at optimum governed speed which is most favorable
from the view point of engine's life and fuel consumption.
When the engine is installed on a certain equipment, it is recommended that the continuous output required
from the engine be kept below this continuous rated output.

2-3 MAXIMUM TORQUE

The maximum torque is the torque at the output shaft when the engine is producing maximum output at
certain revolution.

– 3 –

2-4 PERFORMANCE CURVES

EH72D

55 (5.61

N-m

(

)

kgf-m

)

20

(

26.8

kW

(HP)

15

(20.1)

HORSEPOWER

45 (4.59

MAXIMUM TORQUE

)

MAXIMUM HORSEPOWER

CONTINUOUS
RATED HP

)

TORQUE

10

(13.4)

5

(

)

6.7

2000 2400 2800 3200 3600

REVOLUTION r.p.m

RECOMMENDED
HORSEPOWER RANGE

– 4 –

3. FEATURES

Highly rigid structure

●

High-carbon steel, forged crank shaft

●

Light-weight , tough alminum forged connectiong rod

●

Ball-bearing

●

Special cast iron cylinder liner

Long-lasting structure

●

Forced pressure lubrication of crankshaft by directly connected trochoid pump

●

Standard equipped oil cooler ensures a good lubrication environment

●

Ball bearing installed in the throttle bearing of the carbureter

Reliability

●

Unusually high dust proofing by a double compartment air cleaner and inner vent type carbureter

●

Carbureter equipped with acceleration pump, and receives excellent throttle response.

●

A fine distribution suction pipe and effective combustion chamber shape provide greater cubustion
stability and reduced gas emissions

Compact

●

Center height 133.3mm and 25HP

●

90°V2 cylinder built in crankcase

– 5 –

Fig. 4-1

Fig. 4-2

Fig. 4-3

4. GENERAL DESCRIPTION OF ENGINE COMPONENTS

ROBIN EH72D engine is air-cooled, 4-stroke, twin-cylinder, OHV arrangement gasoline engine. The twin­cylinder is located in the angle of 90 degree; #1 cylinder is in the RH side and #2 cylinder in LH side as
viewed from flywheel (cooling fan) side.

4-1 CYLINDER AND CRANKCASE

The twin-cylinder and crankcase is single piece
aluminum die-casting.
The cylinder liner, made of special cast iron, is
molded into the aluminum casting.
The crankcase has a mounting surface on the output
shaft side, where the main bearing cover is attached.

4-2 MAIN BEARING COVER

The main bearing cover is an aluminum die-casting,
which is mounted on the output shaft side of the
crankcase.
Pilots and bosses are machined on the cover for
direct mounting of the engine onto such machines as
generators and pumps.
It is easy to inspect inside of the engine, after
removing the main bearing cover.

4-3 CRANKSHAFT

The crankshaft is forged carbon steel, and the crank
pin is induction-hardened.
The output end of the shaft has a crankshaft gear
pressed into position.
Engine oil passages are provided onto the journal
and pin portions of crankshaft for lubrication.

4-4 CONNECTING ROD AND PISTON

The connecting rod is forged aluminum alloy, and its
large and small ends function as bearings.
The piston is an aluminum alloy casting, and carries
two compression rings and one oil ring.

– 6 –

Fig. 4-4

4-5 PISTON RINGS

The piston rings are made of special cast iron.
The profile of the top ring is barrel face and the second ring has a tapered face.
The oil ring is designed for better sealing and less oil consumption, in combination with 3 pieces.

4-6 CAMSHAFT

The camshaft is made of special cast iron and
camshaft gears are casted together in one piece.
Each 2 cam robs are provided for intake and
exhaust valves correspondingly.
Both sides of the shaft fit into the plane bearings on
the crankcase and main bearing cover.

Fig. 4-5

Fig. 4-6

1

2

3

1

2

3

TOP
RING

SECOND
RING

OIL
RING

BARREL

TAPER

COMBINATION
RING

– 7 –

4-7 CYLINDER HEAD

The cylinder head is an aluminum die-casting which
utilizes semi-spherical type combustion chamber for
the high combustion efficiency.

Fig. 4-7

4-8 VALVE ARRANGEMENT

The intake valve is located on flywheel side of the
cylinder head.
The cooling fins and passages design lead cooling
air to the exhaust valve area for the optimum
cooling.
Hard alloy valve seats are molded in the cylinder
head.

Fig. 4-8

4-9 GOVERNOR SYSTEM

The governor is a centrifugal flyweight type which
ensures constant operation at the selected speed
against load variations.
The governor gear with governor weights is installed
inside of main bearing cover and driven by the
crankshaft.

Fig. 4-9

INTAKE VALVEEXHAUST VALVE

GOVERNOR
GEAR

– 8 –

4-10 COOLING SYSTEM

The large fins on the flywheel provide sufficient
cooling air capacity for cylinder and cylinder head.
The cylinder baffle helps the cooling air flow
efficiently.

4-11 LUBRICATION SYSTEM

The engine is furnished with full pressure lubrication
system.
The trochoid type oil pump is driven by crankshaft
and delivers pressurized engine oil through the full­flow type oil filter to the journal and pin portions of
crankshaft and camshaft.

4-12 IGNITION SYSTEM

The ignition system is a transistor controlled
magneto ignition system which consists of a flywheel
and an ignition coil with a built-in transistor installed
onto the crankcase.

Fig. 4-10

Fig. 4-11b

Fig. 4-11a

4-13 CHARGING SYSTEM

Multipolar charging coil is provided inside of flywheel. Charging capacity is 12V-15A or 12V-30A.

(12V-15A) (12V-30A)

IGNITION COIL

FLYWHEEL

CABLE, EXTENDED

CHARGE COIL

REGULATOR

REGULATOR

CHARGE COIL

– 9 –

4-14 CARBURETOR

The engine is equipped with a down draft carburetor
that has a float controlled fuel system and a fixed
main jet.
The carburetors are calibrated carefully for the sure
starting, low fuel consumption and sufficient output.
Fuel cut solenoid valve is provided to prevent engine
running on when the key switch is turned to off.
Accelerator-pump is provided for obtaining quick and
good throttle response.

4-15 AIR CLEANER

The air-cleaner is a heavy-duty type with a dual
element system ; primary side is urethane foam
(half-wet) and secondary side is dry type.

Fig. 4-12

Fig. 4-13

4-16 FUEL PUMP

The engine is equipped with a diaphragm type fuel
pump which is operated by the crankcase inside
vacuum pressure.

Fig. 4-14

FUEL CUT
SOLENOID VALVE

ACCELERATOR-PUMP

CLEANER COVER

WING NUT

ELEMENT

URETHANE FOAM

FUEL PUMP

– 10 –

4-17 SECTIONAL VIEW OF ENGINE

Fig. 4-15

CARBURETOR

INTAKE MANIFOLD

IGNITION COIL

OIL PUMP

FLYWHEEL

P.T.O.SHAFT

MAIN BEARING COVER

OIL PUMP FILTER

– 11 –

Fig. 4-16

– 12 –

5. DISASSEMBLY AND REASSEMBLY

5-1 PREPARATIONS AND SUGGESTIONS

When disassembling the engine, memorize the locations of individual parts so that they can be reassembled
correctly. If you are uncertain of identifying some parts, it is suggested that tags be attached to them.
Have boxes ready to keep disassembled parts by group.
To prevent losing and misplacing, temporarily assemble each group of disassembled parts.
Carefully handle disassembled parts, and clean them with washing oil if necessary.
Use the correct tools in the correct way.
When disconnecting electric wirings, be sure to hold and disconnect the connector housing.

5-2 SPECIAL TOOLS

No Special Tool is needed for disassembling and reassembling the engine.
For pulling off the flywheel, universal type puller being popular in the market place as shown in the illustration
is needed.

Fig. 5-1

Tool No. Tool Use

228-95001-17

Flywheel puller with bolt

EH63,64,65,72 / DY30,35,41,42

FLYWHEEL PULLER

– 13 –

5-3 DISASSEMBLY PROCEDURES

Step Parts to remove Remarks and procedures Fasteners

1 Engine oil drain

Drain engine oil by removing plugs located on
both side of crankcase.

2 Muffler cover

M6 x 12 : 6 pcs.

3 Muffler M8 nut : 4pcs.

4 Muffler bracket

M8 x 16 bolt and
washer : 2pcs.

Fig. 5-2

OIL LEVEL GAUGE

M6 FLANGE
BOLT : 2 pcs.

STEP 2

OIL FILLER CAP

GUIDE, oil level

MUFFLER
COVER

M6 FLANGE
BOLT : 2 pcs.

MUFFLER

STEP 3

MUFFLER
BLACKET

M8 BOLT &
WASHER : 2 pcs.

M6 FLANGE
BOLT : 2 pcs.

A

STEP 4

A

GASKET

M8 SUS FLANGE
NUT : 4 pcs.

GASKET

OIL DRAIN PLUG
(

ON BOTH SIDE

STEP 1

)

– 14 –

Step Parts to remove Remarks and procedures Fasteners

5 Air cleaner cover and elements Remove breather pipe from #1 cylinder head.

6 Air cleaner base

M6 x 12 : 3 pcs.

Fig. 5-4

Fig. 5-3

BREATHER PIPE

M6 FLANGE
BOLT :

3 pcs.

STEP 6

WING NUT

CLEANER

COVER

STEP 5

CLEANER
ELEMENT

CLEANER BASE

HOSE CLAMP

BREATHER PIPE

HOSE CLAMP

– 15 –

Step Parts to remove Remarks and procedures Fasteners

7 Blower housing

M6 x 12 : 2 pcs.
M6 x 14 : 6 pcs.

8 Chock control lever and link

(1) Remove the choke knob.
(2) Remove the choke contol link.

M6 bolt : 1 pc.

Fig. 5-5

LINK PIVOT

CHOKE
CONTROL ROD

RETURN
SPRING

STEP 8

CHOKE
CONTROL
LINK

WAVED
WASHER

M5 TAPPING
SCREW : 1 pc.

CLAMP

CHOKE
KNOB

BLOWER HOUSING

M6 FLANGE
BOLT : 2 pcs

STEP 7

M6 FLANGE
BOLT : 6 pcs

– 16 –

Step Parts to remove Remarks and procedures Fasteners

9

Carburetor

At first remove fuel pipe.
Take out carburetor along with governor rod
and rod spring.

M8 x 80 : 2 pcs.

Fig. 5-7

Fig. 5-6

M8 FLANGE
BOLT : 2 pcs.

STEP 9

CARBURETOR

FUEL PIPE

GASKET,
carburetor

– 17 –

Step Parts to remove Remarks and procedures Fasteners

10

Governor lever and
Speed control lever

Governor lever ;
Remove bolt and take out lever.
Speed control lever ;
(1) Governor spring
(2) Self lock nut
(3) Stop plate
(4) Spring washer
(5) Speed control lever

M6 x 12 : 3 pcs.
M6 self-lock nut

11 Speed control bracket unit

M6 x 12 : 3 pcs.

12 Starting motor

At first remove wiring. M8 x 65 : 2 pcs.

Fig. 5-8

M6 NUT : 1 pce.

M6 BOLT
AND WASHER : 1 pce.

M6 SELF LOCK
NUT : 1 pce.

ROD
SPRING

GOVERNOR
ROD

STOP PLATE
SPRING WASHER

STEP 10

FRICTION
WASHER

SPEED CONTROL
LEVER

M8 FLANGE
BOLT : 2 pcs.

STARTING MOTOR

STEP 12

SPACER

GOVERNOR
LEVER

GOVERNOR
SPRING

FRICTION
WASHER

M6 FLANGE
BOLT : 3 pcs.

STEP 11

BRACKET UNIT,
speed control

Fig. 5-9

– 18 –

Step Parts to remove Remarks and procedures Fasteners

13 Fuel pump Remove pluse pipe at first. M6 x 12 : 2 pcs.

14

Ignition coil (1) Take out plug cap.

(2) Remove ignition coil.
(3) Cut out stop wire fixing bands.
(4) Disconnect stop wires from ignition coil.

M6 x 30 bolt &
washer : 4 pcs.

Fig. 5-10

PLUG
TERMINAL

SPARK
PLUG CAP

IGNITION
COIL

TO STOP DIODE

M6 BOLT AND
WASHER ASSY : 2 pcs.

M6 BOLT
AND WASHER
ASSY : 2 pcs.

STEP 14

IGNITION
COIL

PLUG TERMINAL

SPARK PLUG CAP

IGNITION COIL

BRACKET,
fuel pump

HOSE CLAMP

PULSE PIPE

STEP 13

M6 FLANGE
BOLT : 2 pcs.

HOSE CLAMP

FUEL PIPE

M6 FLANGE
BOLT : 2 pcs.

FUEL PUMP and
FUEL FILTER ASSY

HOSE CLAMP

– 19 –

Step Parts to remove Remarks and procedures Fasteners

15 Flywheel

Remove key from crankshaft and then pull
out flywheel by using puller.

M18 nut, washer,
spring washer

16 Charge coil

M5 x 20 : 4 pcs.(15A coil)
M5 x 25 : 4 pcs.(30A coil)

Fig. 5-12

Fig. 5-14

Fig. 5-11

Fig. 5-13

M5 BOLT AND
WASHER : 4 pcs.

STEP 15

M6 BOLT AND
WASHER : 4 pcs.

M18 NUT : 1pce.

SPRING
WASHER

WASHER

CHARGE COIL

STEP 16

FLYWHEEL PULLER

COOLING FAN

FLY WHEEL

RING GEAR