EY08 - Jacks Small Engines

ROBIN 

ROBIN AMERICA, INC. 

ROBIN TO WISCONSIN ROBIN 

ENGINE MODEL CROSS REFERENCE LIST 

EY08 

EY15 

EY 15V 

EY20 

EY2OV 

EY23 

EY28 

EY3 5 

EY40 - 

EY45V 

EY2 1 

EY44 

EY 18-3 

EY25 

EY27 

EH11 

EH12 

EH15 

EH17 

EH21 

EH25 

EH30 

EH30V 

EH34 

EH34V 

EH43V 

EC13V 

DY23 

DY27 

DY30 

DY3 5 

DY4 1 

SIDE VALVE 

OVERHEAD VALVE 

TWO CYCLE 

DIESEL 

WISCONSIN ROBIN 

W 1-080 

W1-145 

W1-145V 

W1-185 

W1-185V 

W1-230 

W 1-280 

W 1-340 

W 1-390 

Wl-45OV 

EY21W 

EY44W 

EY18-3W 

EY25W 

EY27W 

WO1-115 

wo1-120 

WO1-150 

WO1-170 

wo1-210 

WOl-250 

WO 1-300 

WO1-300V 

WO1-340 

WO 1 -340V 

WO 1-43 OV 

WT1-125V 

WRD 1-230 

WRD 1-270 

-1-300 

WRD1-350 

WRD1-410 

0 

0 

0

CONTENTS 

Section Title Page 

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

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

2-1 Maximum Output .......................................... 2 

2-2 Continuous Rated Output .................................... 2 

2-3 Maximum Torque and Fuel Consumption Ratio at Maximum Output ........ 2 

3 . FEATURES .................................................. 3 

4 . GENERAL DESCRIPTION of ENGINE CONSTRUCTION ................... 4 

4-1 

4-2 

4-3 

4-4 

4-5 

4-6 

4-7 

4-8 

4-9 

4-10 

4-1 1 

4-12 

4-13 

4-14 

Cylinder. Crankcase ........................................ 4 

Main Bearing Cover ......................................... 4 

Crankshaft .............................................. 4 

Connecting Rod and Piston ................................... 5 

Camshaft ............................................... 5 

Valve Arrangement ......................................... 5 

Cylinder Head ............................................ 6 

Governor ............................................... 6 

Cooling ................................................. 6 

Lubrication .............................................. 6 

Ignition ................................................ 7 

Carburetor .............................................. 7 

Air Cleaner .............................................. 7 

Sectional View of Engine ..................................... 8 

5 . DISASSEMBLY and REASSEMBLY .................................. 10 

5- 1 Preparation and Suggestion .................................... 10 

5-2 Special Tools ............................................. 10 

5-3 How To Disassemble ........................................ 12 

5-4 How To Reassemble ........................................ 16 

6 . MAGNETO ................................................... 24 

6-1 Magneto ................................................ 24 

6-2 Magneto Trouble Shooting .................................... 24 

7 . GOVERNOR ADJUSTMENT ....................................... 25 

8 . CARBURETOR ................................................ 26 

8-1 Operation and Construction ................................... 26 

8-2 Disassembly and Reassembly .................................. 27

Section Title Page 

9 . BREAK-IN OPERATION Of REASSEMBLED ENGINE ..................... 28 

10 . ROBIN SOLID STATE IGNITION ENGINE (U.T.C.I.) ..................... 29 

10-1 Features ................................................ 29 

10-2 Basic Principle of U.T.C. I ..................................... 29 

I1 . ROBIN OIL SENSOR SYSTEM (FLOAT SYSTEM) ....................... 30 

11-1 Features ................................................ 30 

11 -2 Basic Principle ............................................ 30 

11 -3 Checking Procedures ........................................ 32 

11 -4 Precautions .............................................. 33 

11-5 Wiring ................................................. 33 

12 . TROUBLE SHOOTING ........................................... 34 

12- 1 Starting Difficulties ......................................... 34 

12-2 Engine Misfires ............................................ 35 

12-3 Enginestops ............................................. 35 

12-4 Engine Overheat ........................................... 35 

12-5 Engine Knocks ............................................ 36 

12-6 Engine Backfires through Carburetor ............................. 36 

13 . INSTALLATION ............................................... 37 

13-1 Installing ................................................ 37 

13-2 Ventilation .............................................. 37 

13-3 Exhaust Gas Discharge ....................................... 37 

13-4 Power Transmission to Driven Machines ........................... 37 

13-5 Wiring ................................................. 38 

14 . CHECKS and CORRECTIONS ...................................... 39 

15 . TABLE of CORRECTION STANDARDS ............................... 40 

16 . MAINTENANCE and STORING ..................................... 45 

16-1 Daily Checks and Maintenance ................................. 45 

16-2 Every 20 Hours Checks and Maintenance .......................... 45 

16-3 Every 50 Hours (IO days) Checks and Maintenance .................... 45 

16-4 Every 100 . 200 Hours (Monthly) Checks and Maintenance . ............. 45 

16-5 Every 500 . 600 Hours (Semiannual) Checks and Maintenance . ........... 46 

16-6 Every 1000 Hours (Yearly) Checks and Maintenance ................... 46 

16-7 Preparation for Long Abeyance ................................. 46

1. SPEC1 FICATIOMS 

Bore x Stroke (in) 

Piston Displacement (cu. in) 

Model EY08D 

EY08BN 

Air-Cooled, 4-Cycle, Vertical, Single Cylinder Gasoline Engine 

51 mm 'x 38 mm (2.01" x 1.50") 

77.6 cc (4.74 cu. in) 

Compression Ratio 6.5 

Continuous Rated Output (HP/rpm) 

Max. Output (HP/rpm) 

Max. Torque (kg-m/rpm) 

1.0/3000 

1.4/3600 

2.0/4200 

0.36/3200 

1 .O? 1 500 

1.4/1800 

2.0/2 1 00 

0.72/1600 

Direction of Rotation 1 Counterclockwise Facing to P.T.O. Shaft Clockwise Facing to P.T.O. Shaft 

Cooling System I Forced Air Cooling 

~~ 

~ 

Lubrication Splashing Type 

Lubricant Automobile Oil Class SC 

Carburetor Horizontal Draft, Float Type 

Fuel 

Fuel Consumption Ratio (gr/Hp-h) 

~~ 

Non-leaded Automobile Gasoline 

320 at continuous rated output operation 

Fuel Feed I Gravity Type 

Fuel Tank Capacity I Approx. 1.5 liter (0.40 U.S. gal.) 

Reduction Ratio I - 1 /2 

Speed Governor 

Spark Plug 

Lighting Capacity (V-W) 

Starting System 

Dry Weight (Ibs.) 

Dimensions 

System 

Length (in) 

Width (in) 

Height (in) 

Flywheel Magneto Type (Solid State Ignition) Ignition 

8 kg (17.6 Ibs.) 

-1 - 

Centrifugal Flyweight Type 

NGK-BM4A (S.T.D.) 

- 

Recoil Starter 

252 mrn (9.92") 

264 mm (10.39") 

326 mm (12.83") 

8.5 kg (18.7 Ibs.)

2. PERFORMANCE 

2-1 MAXIMUM OUTPUT 

The maximum output of an engine is such standard power as developed by the engine, after its initial break-in 

period with all the moving parts properly worn in, when operating with a fully open throttle valve, Therefore, 

a new engine may not develop the maximum output in the beginning because the moving parts are not in a 

properly worn-in condition. 

2-2 CONTINUOUS RATED OUTPUT 

The continuous rated output of an engine is such power as developed by that engine when running continuously 

at an optimum speed, and most favorable from the viewpoint of engine life and fuel consumption ratio, 

with the governor in operation. It is suggested, therefore, that when designing a driving system for any mechanism, 

with this engine as prime mover, the continuous power requirement of that mechanism be kept below 

the continuous rated output specified. 

2-3 MAXIMUM TORQUE and FUEL CONSUMPTION RATIO at MAXIMUM OUTPUT 

These mean the maximum torque of the output shaft and fuel consumption ratio at the maxiumum output 

of an engine. 

L 

W 

0 

a 

HP 

3’ 

L 

0 

I 

2.5 

2.0 

1.5 

1 .o 

0.5 

PERFORMANCE CURVE 

MODEL EY08D 

( ) for BN type 

0.45 (0.9) kg-rn 

2000 3000 4000 

(1 000) (1 500) 

- 

(2000) 

Revolution 

r.p.m. 

-2- 

0.40 

0.35 

0.30

3. FEATURES 

1. Compact, lightweight, durable, powerful 4cycle air cooled engine embodying ingenious design techniques 

and skilful workmanship. 

2. Simple construction, smart appearance, maximum easiness of start owing to automatic decompression 

device 

3. Pointless Solid State ignition system is newldy adopted for preventing poor igniting. 

4. Reliable prime mover for varietyof purposes with smooth speed controlrby a governor under varying load 

conditions. 

5. Economical because fuel consumption is very low 

-3-

4. GENERAL DESCRIPTION of ENGINE CONSTRUCTION 

4-1 CYLINDER, CRANKCASE 

The cylinder and crankcase are single piece aluminum 

die casting. The cylinder liner, made of special 

cast iron, is built into the alminum casting. The intake 

and exhaust ports are located on one side of 

the cylinder, and are also inserted into the casting. 

The crankcase is separable on the output shaft side, 

where the main bearing cover is attached to it. 

(See Fig. 1 .) 

4-2 MAIN BEARING COVER 

Fig. 1 

The main bearing cover made of aluminum die casting is built onto the output shaft side of the crankcase so 

that the inside of the engine can readily be checked by simply removing the cover. It is provided with a flange 

and boss for directly mounting machines, such as generators and pumps. 

Two oil gauges also serving as oil filler caps can be mounted. (See Fig. 2 and Fig. 3.) 

Oi I 

4-3 CRANKSHAFT 

Fig. 2 

Ring for Centering 

!ID Oil Gauge 

The crankshaft is forged of carbon steel, and the 

crankpin is induction-hardened. It has a crank gear 

pressure-fitted on the output end. (See Fig. 4.) 

-4- 

Induction Hardening 

(Portion of Crankpin) 

\ 

~~ 

Fig. 3 

Crank Gear (Pressure-fit) 

Fig. 4

4-4 CONNECTING ROD and PISTON 

The connecting rod is made of aluminum die casting, 

which itself serves as bearings at both the large and 

small ends. The large end cap and the oil scraper are 

moulded in a unit for splashing the lubricating oil. 

The piston is cast of aluminum alloy, and has grooves 

for receiving two compression rings and one oil ring. 

(See Fig. 5.) 

4-5 CAMSHAFT 

In the EY08D engine, the camshaft is integrally built 

with a cam gear of special cast iron, and has intake 

and exhaust cams. Also the camshaft has aluminum 

plain bearings attached to both ends. (No ball bearing 

is used.) (See Fig. 6.) 

In the EY08BN engine, the camshaft is forged of carbon 

steel and is provided with a force-fit cam gear. 

@ It serves also as the driving shaft, being driven at half 

the crankshaft speed, and a ball bearing is used at 

the P.T.O. shaft side. 

4-6 VALVE ARRANGEMENT 

The intake valve is located upstream of the cooling 

air with the result that the carburetor is intensively 

cooled. (See Fig. 7.) 

-5- 

L 

\I 

Fig. 5 

:Fig. 6 

Fig. 7 

Top Ring 

Second Ring 

Oil Ring 

Connecting Rod 

Oil Scraper 

Direction of 

Cooling Wind

4-7 CYLINDER HEAD 

The cylinder head is an aluminum die casting, and 

forms a Ricardo type combustion chamber with 

ample area for high combustion efficiency. 

(See Fig. 8.) 

4-8 GOVERNOR 

The governor is a centrifugal flyweight type which 

permits constant operation- at the selected speed 

against load variations. Govrnor gear is installed on 

the bearing cover without fail, and it engages with 

the cam gear after reassembling. (See Fig. 9.) 

4-9 COOLING 

I 

Main Be 

Fig. 8 

Spacer 

- 

Governor Gear Complete 

Q 

Fig. 9 

!mor Sleeve 

The cooling fan serving also as a flywheel cools the cylinder and the cylinder head by forced air cooling. Cyl- 

inder baffles and head cover are provided for guiding the cooling air. 

4-10 LUBRICATION 

The rotating and sliding parts are being lubricated 

by scooping and splashing the oil in the crankcase 

with the oil scraper. (See Fig. 10.) 

-6- 

Fig. 10

4-11 IGNITION 

The ignition system is a flywheel magneto type with 

ignition timing set at 25" before TDC. The magneto 

is composed of a flywheel and ignition coil. The flywheel 

serving also as a fan is mounted directly on the 

crankshaft, and the ignition coil in the crankcase. 

(For further details, refer to Section on the Magneto.) 

(See Fig. 1 1 .) 

4-12 CARBURETOR 

A horizontal draft carburetor is employed. It has 

been carefully set after thorough tests to assure satisfactory 

start up, acceleration, fuel consumption, output 

performance, etc. 

For construction and order details, refer to the Section 

on Carburetor Construction, Disassembly and 

@ Reassembly. (See Fig. 12.) 

4-13 AIR CLEANER 

The air cleaner of the standard ty :ngine is an 0 b- 

long type using a sponge element. (A cyclone type 

semi-wet double element air cleaner is optionally 

available.) (See Fig. 13.) 

-7- 

I Ignition Coil 

Air Cieaner for 

Standard Type 

Fig. 1 1 

Fig. 12 

Fig. 13 

Cyclone Type 

(Option)

4-14 SECTIONAL VIEW of ENGINE 


-8-

Stop Button 

Connecting Rod 

Crankcase 


-9- 

Air Cleaner 

Carburetor 

Intake and 

Exhaust Valve 

Tappet 

Camshaft 

Governor Shaft

5. DISASSEMBLY and REASSEMBLY 

5-1 PREPARATIONS and SUGGESTIONS 

1) When disassembling the engine, remember well the locations of individual parts so that they can be reas- 

sembed correctly. If you are uncertain of identifying some parts, it is suggested that tags be attached to 

them. 

2) Have boxes ready to keep disassembed parts by group. 

3) To prevent missing and misplacing, temporarily assemble each group of disassembed parts. 

4) Carefully handle disassembed parts, and clean them with washing oil. 

5) Use the correct tools in the correct way. 

5-2 SPECIAL TOOLS 

For your reference, the following shows special tools of Robin Engine for Disassembly, Measuring and Inspec- 

tion Instruments. 

Part No. 

2099500407 

2309500107 

2079500307 

2309500207 

2059500107 

Tool 

Flywheel Puller 

(with bolt) 

Valve Spring 

Retainer 

Valve Guide 

Puller 

Use 

For pulling off 

Flywheel 

For mounting and 

dismounting Valve 

Spring Retainer 

and Retainer Lock 


Valve guide 

Applicalbe 

Model 


EY10, 13, 14 

EY 15,18, 20 

EY23, 25, 27, 

EY33 

EY35,40,44 

EC05.07, 10 

EC17,25.37 


EY10,13, 14 

EY 15, 18,20 

EY23 

EY25.27, 33 

EY35,40,44 


EY10 

EY13, 14 

-10- 

Shape

Part No. 

2069500107 

2279500107 

207 95001 07 

“20248 

Tool 

Valve Guide 

Puller 

Timing Tester 

Use 


Valve guide 

For adjusting 

timing 

Applicalbe 

Model 

EY18.23 

EY 15,ZO 

EY25, 27 

EY10, 13, 14 

EY 15, 18,20 

EY25,27,33 

EY35,40,44 

EC03,04,05 

EC07,10, 17 

EC25,37 

- 11 - 

Shape

5-3 HOW TO DISASSEMBLE 

Order 

5 

I tern 

Fuel tank 

Recoil starter 

Tank bracket 

Head cover 

Fan cover 

Muffler cover 

Muffler 

Air cleaner 

L 

*Length of the bolt indicates the length from the bolt head bottom surface to the threaded end. 

Procedures 

(1) Close the fuel cock. 

(2) Disconnect the fuel pipe between the fuel 

strainer and carburetor at the carburetor 

side. 

(3) Remove the fuel tank from the tank bracket. 

M6 x 14 mm bolt : 3 pcs. 

(1) Remove the recoil starter. 


(1) Remove the tank bracket, the head cover, 

and the fan cover from the crankcase and 

the cylinder head. 

M6 x 10 rnm bolt : 2 pcs. 

M6 x 12 bolt : 1 pce. 

M6 nut : 2 pcs. 

(1) Remove the muffler cover 1 from the 

muffler. 


(2) Remove the muffler from the cylinder 

portion of the crankcase. 

M6 x 28 mrn bolt : 1 pce. 

M6 x 50 mm bolt : 1 pce. 

(1) Remove the air cleaner cover and the 

element. 

(2) Remove the air cleaner case from the 

carburetor. 

M6 nut : 2 pcs. 

(3) Disconnect the breather pipe. 

Governor Lever 

Governor Spring 

Lock Bolt 

Governor Shaft 

Sems bolt 

Remarks 

Fastened together 

Remove the primary 

wire of the stop but- 

ton. 

Air cleaner is fasten- 

ed together with the 

carburetor. 

{--) ,Governor Rod Spring 

Fig. 14 

- 12 - 

Governor Rod 

Lever 

' High Speed Set Screw 

Tool 

10 mm box spanner 

IO mm box spanner 

10 m box spanner 

Ir 10 mm spanner 


x 10 mm spanner 

10 mm box spanner

Order Itern Procedures I Remarks I Too I 

6 Governor lever 

and the relative 

parts 

Carburetor 

Starting pulley 

Flywheel 

(1) Remove the governor Iever from the governor 

shaft. 

M6 x 25 mm bolt : 1 pce. 

(2) Remove the governor rod and rod spring 

from the carburetor. 

(3) Remove the carburetor from the 

cylinder portion of the crankcase. 

Just loosen the bolt, 

unnecessary to take 

out the bolt. 

(1) Remove the starting pulley from the fly- Be careful not to 

wheel. damage the blades of 

M12 nut : 1 pce. the flywheel with a 

Fit a box or socket wrench over the fly- driver and a like. 

wheel nut, and strike it hard with a ham- Strlke counterclockmer 

to remove the nut and spring washer. wise with a hammer. 

(See Fig. 15) 

(1) Remove the flywheel from the crankshaft. Fit the flywheel 

puller as shown in 

Fig. 16, turn the 

center bolt clock- 

wise and pull out 

the flywheel. 

Fig. 15 

~ ~~~~~~~~~~~ ~ ~~ 

Order I tern Procedures 

9 Ignition coil (1) Remove the plug terminal from the spark 

plug and remove the ignition coil from the 

crankcase. 


10 (1) Remove the spark plug from the cylinder 

Spark plug 

he ad 

- 13 - 

Fig. 16 

Remarks 


or 10 mm spanner 


or socket wrench 

Sems bolt 710 mm box spanner 

I19 mm box spanner

Order I Item 

\ (-) Driver 

11 Cylinder head 

I 

l2 I 

Intake and 

exhaust valve 

13 I Main bearing 

cover 

\ 

Procedures 

(1) Remove the M6 bolts and remove the cylinder 

head from the crankcase 



(2) Remove the cylinder head gasket from the 

crankcase. 

(1) Remove the inner and outer tappet covers 

from the crankcase. 


(2) Pull out the intake and exhaust valve. 

(3) Remove the valve spring and the valve 

spring retainer. 

(1) From the crankcase remove the bolt fastening 

the main bearing cover. 


(2) Remove the cover, lightly tapping the cover 

evenly with a plastic hammer. 

Fig. 17 

- 14 - 

Remarks 

M6 x 40 mm bolt is 

special bolt. 

Put the notch on the 

outer circumference 

of the spring retainer 

on this side. 

Hook the medium 

size (-) driver at the 

dent (lower side) of 

the spring retainer 

and pull out the 

valves, while pulling 

the spring retainer 

toward you. 

(See Fig. 17.) 

Sems bolt 

I Plastic Hammer 

Be careful not to 

damage the oil seal. 


Fig. 18 

Tool 


The front is this sidf 

(-) driver 


Main/Bearing Cover

15 Tappet 

Order 

16 

17 

18 

Procedures I Remarks I Too I 

(1) Remove the camshaft from the crankcase. To prevent the tappets 

from falling or 

damaging, place the 

crankcase on the 

side. (See Fig. 19 .) 

I (1) Remove the tappets from the crankcase. Before removing put 

a mark of intake or 

exhaust on each 

tappet. 

~~~ ~~~~ ~~~ ~~ 

I tern 

Connecting rod 

and piston 

Piston and 

piston pin 

Crankshaft 

Procedures 

Camshaft 

(1) Scrape off carbon and other foreign deposits 

from the upper parts of the cylinder and 

piston, and then straighten out the bent 

tabs of the lock washers on the connecting 

rod, and remove two pieces of the bolt. 

(2) Remove the lock washer and the connecting 

rod cap from the crankshaft. 

(3) Turn the crankshaft until the piston is raised 

up to the hghest position, push the connecting 

rod up, and remove the piston out of the 

top of the cylinder. 

(1) Remove the two clips, pull out the piston 

pin, and take the piston off from the small 

end of the connecting rod. 

(2) Spread the open ends of the piston rings 

and remove them from the piston. 

(1) Remove the woodruff key (for the mag- 

neto). 

(2) Lightly hammer the magneto end of the 

crankshaft, and pull it out of the crank- 

case. 

- 15 - 

Remarks I Tool 

Pay attention to the 

direction of the con- 

necting rod cap. 


damage the inside of 

the small end of the 

connecting rod. 


break the rings by 

spreading too much. 


damage the oil seal. 


or 8 mm spanner

5-4 HOW TO REASSEMBLE 

.Precaution in reassembling 

Every and each part should be cleaned thoroughly. Especially, pay utmost care and attention to the cleanliness 

of the piston, cylinder, crankshaft, connecting rod and bearings. 

Scrape completely off carbons from the cylinder head and the upper part of the piston; especially the 

carbon adhered in the groove of the piston ring should be carefully and completely taken out. 

Carefully check the lip portion of every oil seal. If faulty one is found, replace it without any hesitation. 

Apply enough oil to the lip portion of the oil seal when reassembling. 

Replace all the gaskets with new ones. 

Replace the key, pin, bolt, nuts, etc. with new one, if necessary. 

Whenever tightening torque is specified, conform to the specified figures. 

Apply oil to the revolutionary parts and friction surfaces, when reassembling. 

Check and adjust the clearances of various portions and then reassemble. 

When some main portions are assembled in the course of reassembling, turn or move the gadgets by hand 

and pay attention to the frictional noise and resistance. 

*Sequence and precautions in reassembling 

5-4-1 GOVERNOR SHAFT 

1) Insert the governor shaft into the crankcase. 

2) Place the clips on the governor shaft. 

5-4-2 CRANKSHAFT 

1) Inser the crankshaft into the crankcase as shown 

in Fig. 20. 

. Note: Be careful not to damage the oil seal lip. 

2) Put woodruff key (for magneto) in place. 

-16- 

Fig. 20 

Shaft

3) Dimensions of Crankshaft Pin 

D (Crankshaft Pin Dia.) 20 dia. -0.037 

- 0.050 

W (Crankshaft Pin Width) 

PISTON TO CYLINDER AT PISTON SKIRT 

THRUST FACE 

tx"--+ 

I 

TOP, SECOND 

PISTON RING GAP 

PISTON RING CLEARANCE 

IN GROOVES i 

CONNECTING ROD TO CRANK PIN 

CONNECTING ROD TO PISTON PIN 

PISTON PIN TO PISTON 

0.008L - 0.047L 

0.2 L - 0.4L 

0.05L - 0.25L (Cutter Ring) 

TOP RING 

0.09OL -0.135L 

SECOND RING 

0.060L - 0.105L 

OIL RING 

0.01OL - 0.065L (Cutter Ring) 

DIA 

0.037L - 0.063L 

0.1 L - 0.7L 

Fig. 21 

- 17- 

0.010L - 0.029L 

0.009T - 0.01OL 

L: LOOSE 

T: TIGHT

5-4-3 PISTON and PISTON RING 

1) If no ring expander is available, install the rings by placing the open ring ends over the first land of the 

piston and spreading the rings only far enough to slip them over the correct ring grooves. 

Note: Pay attention not to break the rings by twisting. Install the oil ring first followed by the second 

ring and then top ring. Meantime, the surfaces of the second ring and the top ring with carved 

carved marks are to be faced up. 

Note: When replacing the piston rings with new ones, install the rings for replacement as shown in Fig. 

22. 

I @ STD I Replacement Parts I 

Top Ring Taper Taper 

I I 

Second Ring Taper Undercut Q l 

2) Reassemble the piston and the connecting rod by 

means of the piston pin. 

Note: Apply enough oil to the small top end of 

the connecting rod. 

Be sure to place the clips on both ends of 

the piston pin. 

3) When installing the connecting rod into place, 

hold piston rings with the ring guide as shown in 

Fig. 24 (if no ring guide is available, keep pressing 

the piston rings with finger tips and gently 

strike the top of the piston with a wooden piece 

or the like to push it in), and check that the symbol 

@ or mark MA on the connecting rod is i 

the direction of the flywheel magneto. 

Note: Apply enough oil to the piston rings, connecting 

rod plain bearings and cylinder 

wall before reassembling. 

Note: The open ends of the piston rings must be 

90" apart from one another on the piston 

periphery. 

Note: The clearance between the piston and cylinder 

must be measured at the piston skirt 

thrust surface. 

a 

Oil Ring Cutter Ring 

Assembly type 

Fig. 22 

- 18 - 

Fig. 23 

Fig, 24 

Crank Case 

(Magneto Side) 

n

5-4-4 CONNECTING ROD 

# 1) Turn the crankshaft to the bottom dead center, 

lightly hammer the piston head until the connecting 

rod contacts the crankpin, and assemble. 

2) When reassembling the connecting rod cap, set it 

so that the oil scraper is in the right.bottom. 


Note: Use new lock washers, and bend the tabs 

securely, 

Note: After reassembly, confirm that the connecting 

rod moves lightly. 

Note: Connecting rod cap tightening torque: 

60 - 80 kg-cm 

Note: For the piston, piston ring and- rod clearance, 

see Fig. 2 1. 

5-4-5 TAPPET and CAMSHAFT 

Insert the tappets back into their holes first, and 

then mount the camshaft. 

Note: Align the timing mark at the root of a tooth 

of the cam gear with the one on the crank 

gear. If the valve timing is wrong, the engine 

cannot operate properly or at all. (See Fig. 

26. ) 

Note: If the intake tappet and exhaust tappet were 

assembled contrarily each other, the tappet 

clearance cannot be kept correctly. 

- 19 - 

Fig. 25 

Fig. 26

5-4-6 MAIN BEARING COVER 

Install the main bearing cover to the.crankcase. 

Note: As the'governor gear is mounted on the main 

bearing cover side, install the main bearing 

cover while checking that it meshes with the 

teeth of the cam gear. (See Fig. 27.) Meantime, 

if the oil seal need be replaced, pressure-fit a 

new oil seal before installing the main bearing 

cover. 

Note: When installing main bearing cover, apply oil 

to the bearing and oil seal lip. Fit the oil seal 

guide over the crankshaft or camshaft to pro- 

tect the oil seal lip from damage. Then place 

the main bearing cover on. 

Check the crankshaft if its side clearance is 

0 - 0.2 mm; and if not, adjust it with the ad- 

justing shim. (See Fig. 28,) 

Note: In the BN type, adjust the side clearance of 

the cam shaft with the adjust shim so that it is 

from 0 to 0.2 mm. 

Note: Main bearing cover tightening torque: 

80 - 100 kg-cm 

Note: Fig. 29 shows one of the methods measuring 

the crankshaft side clearance between the 

machined face of the crankcase and adjusting 

collar. As a paper packing is used on the ma- 

chined face of the crankcase, adjust the clear- 

ance by taking this thickness of0.22 mm into 

account. (See Fig. 29.) 

- 20 - 

-1 

Pay attention to the engagement of 

the governor ear and cam gear. 

I t 

Fig. 27 

Fig. 28 

1 (*-* Dial Indicator 

Ground Surface of 

(The surface of the crankcase is 

to be put together with the sur- 

face of the main bearing cover.) 

Fig. 29

5 -4-7 INTAKE and EXHAUST VALVES 

Remove carbon and gum deposite from the valves, valve seats, intake and exhaust ports and valve guides, 

Note: If the valve face is dinted or warped, replace the valves with new ones. 

Note: If there is an excessive clearance between the valve guide and valve stem, replace the valve guide with a 

spare. For replacing, pull out the valve guide, using the valve guide pulling base and bolts as shown in 

Fig. 30, and pressure-fit a new valve guide into place. 

Valve Face 

% Spring Retainer 

Fig. 30 

VALVE and VALVE GUIDE CLEARANCE 

I A-VALVE FACE I ANGLE 

4 5" I 

I B- SEAT ANGLE I 45" I 

C-GUIDE INSIDE DIA. 5.5 dia. +0.018 

0 

I CLEARANCE MAXIMUM ALLOWABLE 

BETWEEN C and D 

INTAKE 

EXHAUST 

Fig. 31 

- 27 - 

0.020L - 0.050L 

0.056L - 0.092 L 

L: LOOSE

5-4-8 TAPPET ADJUSTMENT 

Lower the tappet all the way down, push the valve, and insert a thickness gauge between the valve and tap- 

pet stem to measure the clearance. (See Fig. 32.) 

Note: The correct tappet clearance for both intake and exhaust valves is 0.1 mm k0.02 mm as measured 

when the engine is cold. 

Fig. 32 

Thickness Gauge 

I Valve 

Valve Spring 

Valve Spring Retainer 

fig. 33 

- Note: If the clearance is smaller than specified, slightly grind the top of the valve stem, and measure it again. 

On the contrary, if the clearance is too large, replace the valve with new one, and polish its contact 

surface with a compound to obtain a good fit. Then adjust the clearance. 

Note: After the tappet clearance adjustment, install the valve springs and the valve spring retainers, and turn 

the crankshaft, and measure the tappet clearance once again if it is correct. 

Note: INSTAL LA TION of SPRING RETAINERS 

Place the notch on the outer circumference of 

the retainer toward this side and insert the re- 

tainer, like pushing in, using a special tool. lf 

a driver is used, insertion may be easier. 

Front should be this side. 

5-4-9 CYLINDER HEAD 

\-I Driver 

‘ \ 

Fig. 34 

Valve Spl k g 

l Retainer 

Remove carbon from the cylinder head, particularly its combustion chamber, and make clean the cooling 

fins. Also check the head for distortion. 

Note: Replace the cylinder head gasket with a new one. 

Note: Cylinder head tightening torque: 90 - 110 kg-cm 

- 22 - 

n 

/”-.

- 

5-4-10 SPARK PLUG 

Tightening torque of the spark plug: 230 - 250 kg-cm. 

Note: If the spark plug is new, tighten the spark plug at 120 - 150 kg-cm torque. 

5-4- 11 IGNITION COIL, FLYWHEEL and STARTER PULLEY 

1) Temporarily fasten the ignition coil to the crankcase, and install the flywheel to the crankshaft. Starting 

pulley is fastened together with the flywheel. 

Note: Before installing, wipe out oil from the crankshaft and the tapered portion of the flywheel. 

Note: Before installing the starting pulley, check if the woodruff key is correctly inserted. 

Note: Flywheel tightening torque: 450 - 500 kg-cm. 

2) After measuring the air gap between the ignition 

coil and flywheel, retighten the ignition coil. 


Air gap: 0.3 - 0.5 mm 

5 -4- 12 CARBURETOR 

I 

Fig. 35 

To the cylinder portion of the crankcase install in the order of the gasket, insulator, gasket and carburetor, 

and then mount the air cleaner case and fasten with two pieces of M6 nut. 

5 -4- 13 GOVERNOR LEVER 

When reassemblying, refer to the 7. GOVERNOR ADJUSTMENT. 

5-4-14 MUFFLER and MUFFLER COVER 

Install the muffler cover 2 to the muffler and fasten the muffler to the crankcase and then install the muffler 

cover 1. 

Note: Muffler tightening torque: 100 - 720 kg-cm 

Note: Clamp the muffler and tighten the bolts after engine the has been fully cooled. 

5-4-15 HEAD COVER, FUEL TANK, FUEL TANK BRACKET and FAN COVER 

Install in the order of the head cover, fan cover, fuel tank bracket and fuel tank. 

Note: Install the grommet of the ignition coil to the head cover before installing the fan cover. 

5-4- 16 RECOIL STARTER 

- With 3 pieces of M6 x 8 mm bolt fasten the recoild starter. 

Note: It is feared that the bolt longer than 8 mm may damage the blade. 

- 23 -

6. MAGNETO 

6-1 MAGNETO 

The spark for ignition is furnished by the magneto assembly. The magneto consists of the flywheel and the 

ignition coil of which flywheel is mounted on crankshaft and ignition coil is mounted in crankcase directly. 

6-2 MAGNETO TROUBLE SHOOTING 

When the engine does not start or starts with difficulty, or when its operation is unstable, the following tests 

will clarify if they are caused by a defect in the magneto. 

1) Check ignition cable for possible corrosion, broken, worm insulator or lose connection. 

2) Check the sparking as described later in this section. 

3) If no spark takes place, replace ignition coil. 

*SPARK TESTING 

Remove the spark plug from the cylinder head and place it on the cylinder head, with the ignition cable 

connected to it. 

Crank the engine several times by recoil starter and observe the spark in the spark gap of spark plug. If 

the spark is strong, the ignition system can be eliminated as the source of trouble. (Remove the primary 

wire from the connector.) 

If the spark is weak or there is no spark at all, repeat the checks. 

The correct electrode gap is 0.6 - 0.7 mm. (Refer to section “14. CHECKS and CORRECTIONS.”) 

Flywheel 

I 

Fig. 36 

- 24 - 

/- 

/“

7. GOVERNOR ADJUSTMENT 

Model EY08 emploies a centrifugal flyweight type governor. The governor is mounted on the govenor gear 

- and the throttle valve of the carburetor is automatically regulated by a lever which is connected to the gover- 

nor in order to maintain constant engine speed against load variations. 

The adjustment procedure of the governor is as follows (See Figs. 37 - 39.): 

1) Connect the carburetor throttle lever to the governor lever with the governor rod and the rod spring and 

mount the governor lever onto the governor shaft. 

2) Install the speed control lever to the crankcase. 

3) Connect the governor lever to the control lever with the governor spring. 


Governor Spring 

Governor Shaft 

b 4) Turn the control lever towards high speed, and 

confirm that the carburetor throttle valve is fully 

opened. Control lever can stay wherever it is 

required. 

*Position to hang the governor spring 

The standard position is 2-A. But, in case of a 

50Hz generator, the governor should be hung at 

3-B . 

5) With a screwdriver in the groove of the governor 

shaft, turn it “clockwise” fully until the governor 

shaft no longer moves, and then look the 

governor lever to the governor shaft with the 

governor lever tightening bolt. (See Fig. 39.) 

Fig. 37 

- 25 - 

Governor Rod 

An example of the governor spring being hooked. 

Fig. 38 


Fig. 39

8. CARBURETOR 

8-1 OPERATION and CONSTRUCTION (See Fig. 40.) 

8- 1 - 1 FLOAT SYSTEM 

The float chamber is located just below the carburetor body and, with a float and a needle valve, maintains 

a constant fuel level during engine operation. 

The fuel flows from the fuel tank into the float chamber through the needle valve. When the fuel rises to a 

specific level, the float rises; and when its buoyancy and fuel pressure are balanced, the needle valve close to 

the shut off the fuel, thereby keeping the fuel at the reference level. 

Main Air Jet 

Float - 

Pilot Jet, ,,"--Pilot Air Jet 

fig. 40 

- 26 - 

r Pilot Jet 

/- 

Needle Valve 

/-

8-1 -2 PILOT SYSTEM 

The pilot system feeds the fuel to the engine during idling and low-speed operation. 

The fuel is fed through the main jet to the pilot jet, where it is metered, and mixed with the air metered by 

the pilot air jet. 

The fuel-air mixture is fed .to the engine through the pilot outlet and the by-pass. 

During engine idling, the fuel is mainly fed from the pilot outlet. 

8- 1-3 MAIN SYSTEM 

The main system feeds the fuel to the engine during medium- and high-speed operation. 

The fuel is metered by the main jet and fed to the main nozzle. The air metered by the main air jet is mixed 

with the fuel through the bleed holes in the main nozzle, and the mixture is atomized out of the main bore. 

It is mixed again with the air taken through the air cleaner into an optimum fuel-air mixture, which is 

supplied to the engine. 

8- 1 -4 CHOKE 

The choke is used for easy start in the cold season. When the recoil starter is pulled with a closed choke, the 

negative pressure applied to the main nozzle increases and draws much fuel accordingly; thus easily start up 

the engine. 

8-2 DISASSEMBLY and REASSEMBLY 

Apart from mechanical failures, most of carburetor troubles are caused by an incorrect mixing ratio, which 

may arise mainly due to a clogged up air or fuel passage in jets, or fuel level variations. In order to assure 

proper flow of air and fuel, the carburetor must be kept clean at all times. The carburetor disassembly and 

reassembly procedures are as follows: (See Fig. 41 .) 

18 

8-2- 1 THROTTLE SYSTEM 

1) Remove the Philips screw (1 8) and throttle valve 

(19), and pull out the throttle shaft (20). 

2) The spirng (21) can be taken out by removing 

the throttle stop screw (22). 

*Exercise care not to damage throttle valve ends. 

8-2-2 CHOKE SYSTEM 

1) Remove the Philips screw (14) and choke valve 

(1 S), and pull out the choke shaft (1 6). 

2) When reassembling the choke shaft, make sure 

that the cutout in the choke valve faces the main 

air jet. 

8-2-3 PILOT SYSTEM 

Remove the pilot jet (23) using correct tool to 

avoid damage to it. 

Reassembly 

Tighten the pilot jet securely. Otherwise, the fuel 

may leak, causing engine malfunction. 

- 27 - 

7 

12 A 

Fig. 4 1 

17

8-2-4 MAIN SYSTEM 

1) Remove the bolt (12) and take out float chamber body (10). 

2) Remove the main jet (1 3) from the body (6). 

3) Reassembly 

a) Fasten the main jet securely to the body. Otherwise the fuel may become too rich and cause engine 

malfunction. 

b) The bolt tightening torque is 70 kg-cm. 

8-2-5 FLOAT SYSTEM 

Pull out the float pin (9) and remove the float (8) and needle valve (1 7). If the needle valve need be re- 

placed, replace it with rubber needle. 

Caution: When cleaning the jets, use neither a drill nor a wire (because of possible damage of the orifice 

which will adversely affect fuel flow). Be sure to use compressed air to blow them clean. 

When removing the needle valve and floats, gently tap the reverse side using the rod more slender than 

the float pin and remove because the float pin is calked to the carburetor body. 

BREAK-IN OPERATION of REASSEMBLED ENGINE 

An overhauled engine must be operated at low speed break-in the parts. A thorough break-in is indispensable 

particularly when the cylinder, piston, piston rings or valves are replaced with new ones. 

The recommended break-in schedule is shown below. 

I 

LOAD 

NO LOAD 3,000 rpm 

NO LOAD 

0.7 PS 

SPEED 

(Crankshafr Rev.) TIME I 

2,500 rpm 

10 minutes 

3,600 rpm 

3,600 rpm 

10 minutes 

10 minutes 

30 minutes 

1.4 PS 3,600 rpm 

60 minutes 

- 28 - 

/-

10. ROBIN SOLID STATE IGNITION ENGINE' (U.T.C.I.) 

b 10-1 FEATURES 

EY08 emploies a pointless ignition system, called Solid State Ignition, which is the circuit breaker type ignition 

device, utilizing the power transistor as an element for controling electric current. This ignition system is 

called U.T.C.I. (Universal Type Transistor Controlled Ignition), and it is based on an external coil system 

in which an ignition coil is installed outside the flywheel and the unit is mounted on an iron core of the coil. 

Being different from the breaker point type ignition system, this brand-new system is completely free from 

such troubles as starting-up failure owing to dirty, burnt or oxidized point surface, lowering of ignition efficiency 

being caused by moisture, rough surface 

mechanical parts. 

to breaker point and incorrect timing resultant from worn 

10-2 BASIC PRINCIPLE OF U.T.C.!. (See Fig. 42.) 

Electricity is generated in the primary ignition coil by rotation of the flywheel, and the current a flows, 

by which the condenser is charged. 

When the flywheel goes round further, direction of the current changes, and the current b flows, causing 

the current c and the current d flow to the power transistor and the transistor for 

condenser8is charged by the current d contrarily to the case 1). 

signals for each. The 

When the flywheel goes round further more, the current generated 

and then begins decreasing. 

in the primary coil gets to its peak, 

Then, voltage between C (Collector) and E (Emitter) of the transistor for signals becomes zero, and the 

transistor is turned OFF, while the current 

thyrister (SCR), thus turning the SCR ON. 

d changes to the current e and goes into the gate of the 

When the SCR is switched ON and the current b flows into the SCR (Current f), the current c flowing 

the power transistor is interrupted abraptly, generating high voltage by the current change in the secondary 

coil, thus giving sparks to the spark plug. 

Fig. 42 

- 29 - 

ignition Coil

1.1. ROBIN OIL SENSOR SYSTEM (FLOAT SYSTEM) 

In the EYOS, an oil sensor is available as a maker option. 

11 - 1 FEATURES 

1) The engine oil sensor detects the quantity of engine oil and automatically stops the engine, if it falls 

below the specified level, to prevent the engine from burning due to oil maintenance failure or for other 

reasons. 

If the oil shortage warning lamp is connected to the connecting terminal for it. the warning lamp is lit 

when the engine stops. 

2) If the engine oilis short when the engine is started, the engine can not be started, even if the recoil starter 

is pulled. If the warning lamp is connected, the lamp is lit to indicate oil shortage. 

3) As the power generated by the igniter is used, any special power supply unit is not necessary. 

4) On-tatch stop is possible also by using the stop button, which is generally incorporated in the unit, based 

on a push button system. (Self-maintaining and automatic restoration circuits are incorporated in the 

unit.) 

5) This system features the malfunction preventing structure depending on outer magnetic field. 

11 -2 BASIC PRINCIPLE 

This oil sensor system consists 

sensor. 

of a flywheeI magneto, an igniter, an oil level controller, and an oil level 

As shown in Fig. 43, when the oil level is above the specified one, the lead switch contact is OFF, and the 

engine can run normally (sensor OFF condition). If the oil becomes short and position of the float in the /" 

sensor case goes down to the specified level shown in Fig. 44, the lead switch contact is turned ON by the 

magnetic field of the permanent magnet incorporated in the float (sensor ON condition). 

When the oil level sensor is turned ON, the current il generated by the counter-electromotive voltage VI in 

the primary ignition coil flows from the primary wire of the igniter via the delaying circuit of the oil level 

controller, both of which are shown in the block diagram. When the current iI generated by the counter 

electromotive voltage VI goes up to a certain level, the current il is loaded to the SCR gate from the delaying 

circuit via the self-maintaining circuit if V, is loaded. 

Then, the SCR is turned ON, thus starting operation of the warning lamp driving circuit, lgighting the warning 

lamp to indicate the oil shortage condition, and completely short-circuiting the regular electromotive 

voltage V, in the primary coil of the igniter for the igniter not to generate sparks. This condition is continued 

until the engine is stopped by the self-maintaining circuit. 

In normal stopping operation of the engine, the current i, generated by the regular electromotive voltage 

V, in the primary coil of the igniter is loaded, via the stop switch, to the self-maintaining circuit of the oil 

level controller. This current is loaded to the SCR gate via the self maintaining curcuit, and the SCR is turned 

ON. When the SCR is turned ON, the driving circuit of the warning lamp starts operating, thus lighting the 

warning lamp, and completely short-circuiting the regular electromotive voltage V, in the primary coil of the 

igniter for the igniter not to generate sparks. 

This condition is continued until the engine is stopped by the self-maintaining circuit. 

In restarting, the engine stopping operation 

gine can be started normally. 

is cancelled by automatically restoring mechanism, and the en- 

- 30 - 

/-

Permanent Magnet , 

Shield Case 7 

[ F d Switch 

Oil Scraper 

,!- Tightening Torque: 

80 - 90kg-cm 

Sensor OFF (Running Mode) 

Fig. 43 

Oil Level) 

.ankcase 

Fig. 45 

-31 - 

Sensor ON (Stop) 

Fig. 44

11-3 CHECKING PROCEDURE 

When the engine can not be started, supply oil up to the maximum oil level, and pull the recoil keeping the 

engine in the horizontal position. Engine oil is supplied up till the maximum level; but it doesn't start yet, 

please check the engine in the following manner. 

1) Oil Level Sensor Checking (See Fig. 46.) 

Disconnect the sensor from the controller, and check with a tester continuity between the sensor lead 

wire (yellow) and the grounding wire of the engine. 

When there is no continuity under the condition that the oil has been supplied up to the specified level 

(about 280 cc), the oil level sensor is normal. If there is continuity, replace it with a new one. 

When there is continuity under the condition that the oil level is below the specified one (200 cc), the 

sensor is normal. If not, replace the sensor with a new one. 

Fig. 46 

2) Oil Level Controller Checking (See Fig. 47) 

Disconnect the sensor from the controller (don't 

disconnect the stop button from the controller), 

and start operation of the stop switch after set- 

ting rpm of the engine at more than 1,200 rpm. 

(Don't continue depressing it, and restore it to 

the normal position soon.) 

Warning lamp is lit in a few seconds and the 

engine is stopped, the controller is normal. If 

the oil warning lamp is not lit and the engine is 

stopped, replace the warning lamp with a new 

one. If the engine does not stop in a few seconds 

(about 2 seconds), inner section of the controller 

is defected, so replace it with a new one. 

-32 - 

Controller 

Stop Switch 

Fig. 47 

111 

/-

- 11 -4 PRECAUTIONS 

- 

1) The oil level sensor used in this controlling system has a float which can automatically detect the oil level 

according to the oil level change. However, if degraded oil, oil of improper grade, or oil with viscocity 

which is not appropriate for the periopheral temperature should 

operate normally and fails in detecting the oil level. 

be used, sometimes the float does not 

2) Don’t drop the 

pull the wire. 

oil level sensor and the oil level controller, nor add any physical impact to them. Don’t 

3) In removing the oil level sensor from or mounting it to the crankcase, be careful not to damage the 

O-ring. Don’t disassemble the oil level sensor removed. 

In cleaning the oil level sensor, use the engine oil. If cleaned with gasoline or kerosene, the O-ring may 

swell. 

4) Mount the oil level sensor under the condition that the crankcase has been fully cooled. 

spanner for tightening the bolts. Tightening torque: 80 - 90 kg-cm. (If a box spanner 

Use a 21mm 

is used, the wire 

may be damaged.) Wire connection should be done as shown in the wiring diagram. Be careful in tightening 

or wiring not to give damages to the wire. 

5) If the warning lamp is broken soon, it suggest the possibility of the warning lamp’s capacity shortage. 

Standard 

Lamp : 6V - 0.6W 

Light emitting diode: 30 mA (ID) 

11-5 WIRING 

Igniter 

- 

E 

Green r 

Oil Level 

m 

3 Controller 

a .- 

m 

Flywheel 

- - 

- 

1 

4” 

I 

+- 

.- 

- 

- m 

m Z E T m 

Oil Shortage 

Connecting Terminal 

Lamp Warning 

Yellow 

I 

I 1 

\ 

Fig. 48 

-33 - 

0 

Oil Shortage 

#e‘1ow 

Warning Lamp - 

- (Crankcase) 

Oil Level Sensor 

Oil Level 

Crankcase

12. TROUBLE SHOOTING 

The following three conditions must be satisfied for satisfactory engine start. 

1. The cylinder filled with a proper fuel-air mixture. 

2. An appropriate compression in the cylinder. 

3. Good sparks at the correct time to ignite the mixture. 

The engine cannot be started unless these three conditions are met. There are also other factors which make 

engine start difficult, e. g., a heavy load on the engine when it is about to start at low speed, and high a back 

pressure due to a long exhaust pipe, just to say a few. 

The most common causes of engine troubles are given below: 

12-1 STARTING DIFFICULTIES 

12- 1 - 1 FUEL SYSTEM 

1) No gasoline in the fuel tank; or the fuel cock is closed. 

2) The carburetor is not choked enough, particularly when the engine is cold. 

3) Water, dust or gum in the gasoline block flow of the fuel to the carburetor. 

4) Inferior grade 

mixture. 

gasoline or poor quality gasoline is not gasfied enough to 

produce 

the correct fuel-air 

5) The carburetor needle valve is held open by dirt or gum. This trouble can be detected as the fuel flows 

out of the carburetor when the engine is idling. (Overflow) 

This trouble may be remedied, depending on cases, by lightly tapping the float chamber with the grip of 

a of the like. screwdriver 

r 

6) If the carburetor overflows, excessive fuel runs into the cylinder when starting the engine, making the 

fuel-air mixture too rich to burn. If this happens, remove the spark plug, and pull the recoil starter a few 

turns in order to let the rich fuel-air mixture out of the spark plug hole into the atmosphere. Keep the 

carburetor choke open during this operation. Dry the spark plug well, screw it into place, and try to start 

again. 

12- 1 - 2 COMPRESSION SYSTEM 

If starting difficulties and loss of power are not due to the fuel system or ignition system, the following must 

be checked for possible lack of compression. 

1) Engine inside is completely dried up because of a long period of non-operation. 

2) Loose or broken spark plug. This causes a hissing noise made by mixture gas running out of cylinder in 

compression stroke during cranking. 

3) Damaged head gasket 

stroke. 

or loose cylinder head. A similar hissing noise is produced during compression 

4) In correct Tappet Clearance 

If the correct compression is not obtained even after remedying the above, 

check further as follows: 

a) Valve stuck open due to carbon or gum on the valve stem. 

disassemble the engine and 

b) If the piston rings are stuck on the piston, remove the piston and connecting rod from the engine, 

and clean, remedy or replace the parts. 

- 34 -

12- 1 - 3 ELECTRICAL SYSTEM 

Check the following for lack of sparks. 

1) Leads of the ignition coil or spark plug disconnected. 

2) Ignition coil damaged and shorted. 

3) Spark plug cable wet or soaked with oil. 

4) Spark plug dirty or wet. 

5) Spark plug electrode gap incorrect. 

6) Spark plug electrodes in contact with each other. 

7) Incorrect spark timing. (Is the flywheel set in the correct position by the key?) 

12-2 ENGINE MISFIRES 

1) Incorrect spark plug electrode gap. Adjust it to anywhere between 0.6 and 0.7 mm. 

2) Ignition cable worn and leaking. 

3) Sparks weak. 

4) Ignition wire connections loose. 

5) Water in gasoline. 

6) Insufficient compression. 

12-3 ENGINE STOPS 

1) Fuel tank empty. Water, dirt, gum, etc. in gasoline. 

2) Vapor lock, i. e., gasoline evaporating in the fuel lines due to overheat around the engine. 

- 3) Vapor lock in the fuel lines or carburetor due to the use of too volatile winter gas in the hot season. 

- 4) Air vent hole in the fuel tank cap plugged. 

5) Bearing parts seized due to lack of oil. 

6) Magneto or ignition coil faulty. 

12-4 ENGINE OVERHEAT 

1) Crankcase oil level low. Add oil immediately. 

2) Spark timing incorrect. 

3) Low grade gasoline is used, or engine is overloaded. 

4) Cooling air circulation restricted. 

5) Cooling air party misdirected causes loss of cooling efficiency. 

6) Cylinder head cooling fins clogged up with dirt. 

7) Engine operated in an ecnlosed space without fresh supply of cooling air. 

8) Exhaust gas discharge restricted, or carbon deposits in the combustion chamber. 

9) Engine running on low-octane gasoline detonates due to heavy load at low speed. 

- 35 -

12-5 ENGINE KNOCKS /- 

1) Low-quality gasoline. 

2) Engine operating under heavy load at low speed. 

3) Carbon or lead deposits in the cylinder head. 

4) Spark timing incorrect. 

5) Loose connecting rod bearing due to wear. 

6) Loose piston pin due to wear. 

7) Causes of engine overheat. 

12-6 ENGINE BACKFIRES through CARBURETOR 

1) Water or dirt in gasoline, or low-grade gasoline. 

2) Intake valve stuck. 

3) Valves overheated, or red-hot carbon particles in the combustion chamber. 

4) Engine cold. 

- 36 -

- 13. INSTALLATfON 

- Engine life, ease of maintenance and inspection, frequency of checks and repairs, and operating cost all de- 

pend on the way in which the engine is installed. Carefully observe the following instructions for installing 

the engine. 

L 

I 

B 

13-1 INSTALLING 

When mounting the engine, carefully examine its position, the method of connecting it to a load (machine), 

the foundation, and the mehtod of supporting the engine. 

When determining its mounting position, in particular, make sure that gasoline and oil can easily be supplied 

and checked, the spark plug can easily be checked, the air cleaner can easily be serviced, and that the oil can 

easily be discharges. 

13-2 VENT1 LATION 

Fresh air is necessary for cooling the engine and burning the fuel. 

In case where the engine is operated under a hood or in a small room, temperature rise in the engine room 

can cause vapor lock, oil deterioration, increased oil consumption, loss of power, piston seizure, shorter 

engine life, etc., making it impossible to operate the engine properly. It is necessary, therefore, to provide a 

duct or baffle to guide cooling air to the engine to prevent recirculation of he hot air used for engine cooling, 

and temperature rise of the load (machine). 

Take steps as necessary to keep the engine room temperature below 50°C even in the hottest period of the 

year. 

13-3 EXHAUST GAS DISCHARGE 

Exhaust gas in noxious. When operating the engine indoors, be sure to discharge the exhaust gas outdoors. If 

a long exhaust pipe is used in such a case, the internal resistance increases causing loss of engine power. Thus 

pipe inside diameter must increase in proportion to exhaust pipe length. 

Exhaust pipe: Less than 3 m long, pipe inside diameter 25 mm, 

Less than 5 m long, pipe inside diameter 30 mm. 

13-4 POWER TRANSMISSION to DRIVEN MACHINES 

13-4- 1 BELT DRIVE 

Take the following notes into consideration. 

* V-belts are preferable to flat belts. 

* The driving shaft of the engine must be parallel to the driven shaft of the load. 

* The driving pulley of the engine must be in line with the driven pulley of the load. 

* Install the engine pulley as close to the engine as possible. 

* If possible, span the belt horizontally. 

* Disengage the load when starting the engine. 

If no clutch is used, use a belt tension pulley or thelike. 

13-4-2 FLEXIBLE COUPLING 

When using a flexible coupling, runout and misalignment between the driven shaft and engine shaft must be 

minimized. Runout and misalignment tolerance are specified by the coupling manufacturer. 

-37 -

13-5 WIRING 

Wire as shown in the wiring diagram below. 

u. T. c. I. 

Ignition Coil 

Fig- 49 

- 38 - 

- 

cn 

3 

n 

5 m 

P 

UJ 

/"

- 

14. CHECKS and CORRECTIONS 

After disassembling and cleaning the engine, check and repair, if necessary, according to the correction table. 

- The correction table apolies whenever the engines are repaired. It is important for the servicemen to be 

familier with the contents of this table. Correct maintenance is recommended by observing the correction 

standards specified. 

The meanings of the terms used in the correction table are as follows: 

Correction 

Repair, adjustment or replacement of any engine parts. 

Correction Limit 

The limit on wear, damage or functional deterioration of engine parts beyond which normal engine performance 

cannot be expected without repairing such parts. 

Use Limit 

The limit beyond which parts can no longer be used in respect of performance or strength. 

Standard Dimensions 

The design dimensions of new parts minum tolerance. 

Correction Tolerance 

Tolerance on the dimensions of engine parts refinished or adjusted. 

- 39 -

ITEM 1 STANDARD 

SIZE 

Piston pin O.D. 11 dia. 

Large end I.D. 20 dia. 

Clearance between 

rod large end I.D. 

and crankpin 

Small end I.D. 11 dia. 


small end I.D. 

and pinston pin 

Large end side 

clearance 

Parallelism between 

large end and 

small end bores 

Distance between 

large end and 

small end bores 

66 

Crankpin O.D. 20 dia. 

Crankpin 0. D. 

roundness 

Crankpin O.D. 

cylindricity 

Crankpin O.D. 

parallelism 

Crankshaft 

journal O.D. 

Drive S. 20 dia. 

Mag. S. 17 dia. 

Drive S. 

Mag. S 

Cam lobe height I 18.4 

Journal O.D. 

I 

Drive S. 

dia, 

Mag. S. 

Mag. S. 10 dia. 

CORRECTION 

TOLERANCE 

0 

-0.008 

+0.013 

0 

0.037-0.063 

+0.021 

+0.010 

0.010-0.029 

0.1 - 0.7 

0.05 

2 0.1 

-0.037 

-0.050 

Less than 0.005 



- 0.003 

- 0.01 2 

io.1 

-0.01 3 

-0.028 

-0.003--0.012 

-0.01 3--0.028 

-IMIT 

USE 

LIMIT 

- 0.04 - 0.04 

+0.1 

0.2 

+0.1 

0.2 

REMARKS TOOL 

Micro- 

meter 

Cylinder 

gauge. 

Micrometer 

CORRECTION 

METHOD 

Replace 

Replace 

Replace 

Cylinder 

+0.08 +0.08 Replace 

gauge 

0.1 2 

1 .o 

0.1 

0.1 2 

1 .o 

0.1 

k0.15 

-0.1 5 -0.1 5 

- 0.05 -0.05 

for D 

17 dia. for BN 

-41 - 

Cylinder 

gauge, 

Micrometer 

Test bar 

and Dial 

gauge 

Micro. 

meter 

Micro- 

meter 

Micro- 

meter 

Dial 

gauge 

Micro- 

meter 

Replace 

Re-machine 

or Replace 

Re-machine 

or Replace 

Re-machine 

or Replace 

Replace 

Micro- 

-0.25 -0.25 Replace 

meter 

-0.05 -0.05 

for D 

for BN 

Micro- 

meter 

Replace

~ 

ITEM 

Valve stem O.D. 


stem and guide + 

Tappet clearance 


groove and retainer 

STANDARD CORRECTION USE 

SIZE TOLERANCE I LIMIT LlMlT 

l z l 

REMARKS 

1-1 

-0.020- -0.032 

5 

Exhaust -0.056 - -0.092 : 

5.5 dia. -0.1 

Intake 0.020 - 0.050 

0.3 0.3 At middle 

Exhaust 0.056 - 0.092 

below 1 

0.1 0 +0.02 above When cold 

0.25 

0.1 - 1 0.3 0.5 0.5 

Stem end length 

' Intake 

3.5 

Exhaust 

-1 .o -1.0 

Total length 20.8 I +0.06 - 0 1 1 -0.5 -0.5 


stem and guide 

Spark plug 

Spark gap 

Spark timing 

NGK BM4A 

25" before 

T.D.C. 

-42 - 

I 

TOOL I 

Vernier 

calipers 

1 1 

CORRECTlOh 

METHOD 

Replace 

Square Replace 

Micro- 

meter 

Cylinder 

gauge 

Feeler 

gauge 

Vernier 

calipers 

Replace 

Replace 

Replace 

Replace 

Vernier 

calipers Replace 

Feeler Adjust or 

gauge replace

ITEM REMARKS CORRECTION LIMIT 

HPIrpm 

2.014200 

Max. Output Below 110% of rated output 

00 

Continuous Rated 

Output 

1.4/3600 

for D 

for BN 2.0121 

for D 

1.411 800 for BN 

ITEM liter/hr CORRECTION PRECISENESS CORRECTION PROCEDURE 

Fuel Consumption I 0.65 I 135% of the standard value and up I 3600 rpm at continuous rated output. 

ITEM I cc/hr I USE LIMIT cc/hr REMARKS 

Lubricant Consumption 10 

50 

ITEM B 

REMARKS 

Fixed Quantity 

of Lubricant 1 0.4 

*Use the SC or higher grade engine oil. 

T 

Comparison between oil viscosity and temparature 

Single 

grade 

Multi- 

grade 

I I I I ' I 

- 

1 OW-30 

ZEEEuLL 

1 -10 0 10 20 30 4OoC 

* If quality and quantity of the engine oil become lower or less, burning might be caused. 

-43 - 

1 

r 

R EMAR KS 

When the peripheral temparature is 

below -2OoC, use the oil of viscosity 

and quality fitted to the local conditions. 

When the peripheral temparature is more 

than 4OoC, use the oil of viscosity and 

quality fitted to the local conditions. 

The oil consumption is apt to increase, 

when used under high peripheral tempa- 

rature, so it is necessary to check every 

day.

al 

3 

0 

t- 

.- 

C 

0, 

Oil Change 

ITEM FREQUENCY OF OIL CHANGE I 

First time: Change oil after 20 hours operation. 

Second Time and Thereafter: Change oil every 50 hours operation. 

ITEM kg/cm2 /rpm 

LIMIT 

REMARKS TOOL CORRECTION 

Cylinder pressure 

ITEM 

Min. accelerating 

revolution 

(S.T.D. Engine) 

ITEM 

Cylinder head bolts 

Connecting rod bolts 

Magneto clamp nuts 

+- 

L Main bearing cover bolts 

cn 

.- 

I- 

Spark plug 

70% of normal value and down 

rPm 

1800 

kg-cm 

900 

90- 110 

60 - 80 

450 - 500 

80 - 100 

ft-lb 

- 44 - 

TOOL 

Tachometer 

TOOL 

Torque wrench 

Torque wrench 

Torque wrench 

Torque wrench 

Torque wrench 

Pressure gauge 

for D 

for BN 

Reference value 

REAM R KS 

REMARKS 

Figures in the parenthesis 

are for mounting a new plug.

- 

- 

16. MAINTENANCE and STORING 

The following maintenance jobs apply when the engine is operated correctly under normal conditions. The 

indicated maintenance intervals are by no means guarantees for maintenance free operations during these 

intervals. 

For example, if the engine is operated in extremely dusty conditions, the air cleaner should be cleaned every 

day instead of every 50 hours. 

16- 1 DAILY CHECKS and MAINTENANCE 

Checks and maintenance Reasons for requiring them 

Remove dust from whatever parts which 

accumulated dust. 

~ ~~ ~ ~~ 

Check external fuel leakage. If any, retighten 

or replace. 

Check screw tightening. If any loose one is 

found, re-tighten. 

Check oil level in crankcase and add up as 

necessary. 

L 16-2 EVERY 20 HOURS CHECKS and MAINTENANCE 

I 


The governor linkage is especially susceptible to 

dust. 

Not only wasteful but also dangerous 

Loose screws and nuts will result in vibration 

accidents. 

If the engine is operated without sufficient oil, 

it will fail. 

Change crankcase oil. To remove run-in wear particles 

16-3 EVERY 50 HOURS (10 DAYS) CHECKS and MAINTENANCE 

I 

I 

Checks and maintenance 

~ ~~ 

Change crankcase oil. 

Clean air cleaner. 

I 

1 

Reasons for 

Contaminated oil accerates wear. 

Clogged air cleaner harms 

requiring I 

I 

engine 

Check spark plug. If contaminated, wash in 

gasoline or polish with emery paper. 

Output power is reduced and starting is made 

difficult. 

16-4 EVERY 100 - 200 HOURS (MONTHLY) CHECKS and MAINTENANCE 


Clean fuel filter and fuel tank. The engine will be out of order. 

-45 - 

1 

I

16- 5 EVERY 500 - 600 HOURS (SEMIANNUAL) CHECKS and MAINTENANCE 

I Checks and maintenance I Reasons for requiring them I 

r 

Remove cylinder head and remove carbon 

deposit. 

Disassemble and clean carburetor. 

The engine will be out of order. 

16-6 EVERY 1000 HOURS (YEARLY) CHECKS and MAINTENANCE 

Checks and maintenance 

Reasons for requiring them 

clean, correct or replace parts. The engine output drops and become out of order. Perform 

1 Change rings. piston 

I I 

Replace fuel pipe once a year. To prevent from danger caused by the fuel 

leakage. 

16-7 PREPARATION for LONG ABEYANCE 

1) Perform the above 16-1 and 16-2 maintenance jobs. 

2) Drain fuel from the fuel tank and carburetor float chamber. 

3) To prevent rust in the cylinder bore, apply oil through the spark plug hole and turn the crankshaft several 

turns by hand. Reinstall the plug. 

4) Turn the starting pulley by hand and leave it where the resistance is the heaviest. 

5) Clean the engine outside with oiled cloth. 

6) Put a vinyl or other cover over the engine and store the engine in dry place. 

- 46 - 

- 

," 

/-

Industrial 

Engines

EY08 - Jacks Small Engines

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