EY35, EY40 - Small Engine Discount

- 

ROBIN AMERICA, INC. 

ROBIN TO WISCONSIN ROBIN 

ENGINE MODEL CROSS REFERENCE LIST 

WISCONSIN ROBIN 

Wf-080 

ROBIN 

EY08 

EY15 

EY 15V 

EY20 

EY20V 

EY23 

EY28 

EY35 


EY45V 

EY2 1 

EY44 

EY 1 8-3 

EY25 

EY 27 

W1-145 

W1-145V 

W1-185 

W1-185V 

W 1-230 

W 1-280 

W 1-340 

W1-390 

W 1 -450V 

EY21W 

EY44W 

- 

EY 18-3 W 

EY25W 

EY27W 

EHll 

EH12 

EH15 

EH17 

EH21 

EH25 

EH3 0 

EH3 OV 

EH34 

EH3 4V 

EH43V 

wo1-115 

wo1-120 

WO1-150 

WO1-170 

wo1-210 

wo1-250 

WO 1-300 

WO 1 -300v 

WO 1 -340 

WO 1 -340V 

WQ 1 -430V 

TWO CYCLE 

EC13V 

WT1-125V 

DlESEL 

DY23 

DY27 

DY30 

DY3 5 

DY4 1 

WRD1-230 

WRD 1 -270 

WRD 1-300 

WRD1-350 

WRD1-410 

1

. 

CONTENTS 

See tion 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 Max . Output ....... 2 

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

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 

4 . 1.5 

4-16 

4-17 

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

Main Bearing Cover ..................................... 5 

Crankshaft .......................................... 5 

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

Camshaft ........................................... 6 

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

Valve Arrangement ..................................... 6 

Governor ........................................... 7 

Balancer ............................................ 7 

Decompression Device ................................... 7 

Cooling Device ........................................ 8 

Lubrication ........................................... 8 

Ignition Device ........................................ 8 

Carburetor .......................................... 9 

Air Cleaner .......................................... 9 

Diode Rectifier ....................................... 9 

Sectional View of Engine ................................. 10 

5 . DISASSEMBLY and REASSEMBLY .............................. 12 

5-1 Preparations and Suggestion ............................... 12 

5-2 Special Tools ......................................... 12 

5-3 How to Disassemble .................................... 13 

5-4 How to Reassemble ..................................... 18 

Tappet Clearance Adjustment .............................. 22 

Ignition Timing Adjustment ............................... 23 

Governor Setting Method ................................. 25

See rion Title Page 

6 . CARBURETOR ............................................ 26 

6-1 Operation and Construction ............................... 26 

6-2 Disassembly and Reassembly .............................. 27 

7 . BREAK-IN OPERATION of REASSEMBLED ENGINE ................. 28 

8 . ROBIN SOLID STATE IGNITION ENGINE (OPTION) ................. 29 

8-1 Features ............................................ 29 

8-2 Basic Circuit and Operating Theory of S.S. I . System ............... 29 

8-3 Checking S.S.I. Unit with Tester ............ : ............... 29 

8-4 Measuring Resistances of Exciter Coil and Pulser Coil .............. 29 

9 . TROUBLE SHOOTING. ...................................... 30 

9-1 Starting Difficulties ..................................... 30 

9-2 Engine Misfires ........................................ 31 

9-3 Enginestops ......................................... 31 

9-4 Engine Overheat ....................................... 31 

9-5 Engine Knocks ........................................ 32 

9-6 Engine Backfires through Carburetor ......................... 32 

10 . INSTALLATION ........................................... 33 

10-1 Installing ............................................ 33 

10-2 Ventilation .......................................... 33 

10-3 Exhaust Gas Discharge ................................... 33 

10-4 Fuelsystem ......................................... 33 

10-5 Power Transmission to Driven Machines ....................... 34 

10-6 Wiring ............................................. 34 

11 . CHECKS and CORRECTIONS .................................. 37 

12 . TABLE of CORRECTION STANDARDS ........................... 38 

13 . MAINTENANCE and STORING ................................. 43 

13-1 Daily and Maintenance .................................. 43 

13-2 Every 20 Hours Checks and Maintenance ...................... 43 

13-3 Every 50 Hours (10 days) Checks and Maintenance ................ 43 

13-4 Every 100 - 200 Hours (Monthly) Checks and Maintenance .......... 43 

13-5 Everv 500- 600 Hours (Semiannual)ChecksandMaintenance ........ 44 

13-6 Every 1000 Hours (Yearly) Checks and Maintenance ............... 44 

13-7 Preparation for Long Abeyance ............................. 44

1. SPECIFICATIONS 

w 

i 

-1-

2. PERFORMANCE 

2-1 MAXIMUM OUTPUT 

The maximum ouput of an engine is such standard power as developed by the engine, after its initial break in period with all 

the m,oving 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- 

- rpm

PERFORMANCE CURVE 

MODEL EY40D 

10 

9 

2.2 (4.4) 

2.1 (4.2) 

t 

kg-m 

8 

7 

I 

HP 

6 

5 

4 

3 

2 

1 

0 

-3-

3. FEATURES 

Small in size, light in weight 

The cylinder and crankcase are of a one-piece aluminum diecast structure, which is light in weight. The dimensions are 

reduced as much as possible for easy mounting. 

Quiet operation with low level of vibration 

Intake and exhaust noises are reduced by use of a newly designed muffler having glass wool and a cyclone cleaner. Ma- 

chine noise is reduced by selection of a suitable cam shaft profile and optimum clearances for inner parts. All ths adds 

up to a quiet engine. Vibration is also reduced to a low level by weight reduction of reciprocating parts, and selection 

of a timing balancer and optimum balance factor. 

Easy to start 

These engines can easily be started because they employ an automatic decompression device and a newly designed re- 

coil starter. 

Wide range of adaptability 

These models are available in various types of output shafts and also a type (Type B) with a built-in 1 /2 reduction gear 

for application to various kinds of machines. The engines have two oil drain ports, and theirecoil starter can be pulled 

in any desired direction. Various optional parts are also available. All these combine to increase adaptability to machines. 

Durable, reliable and safe 

A liner of special cast iron, hard-chrome-plate piston rings, forged rod, etc. are used to make these engines as reliable 

and durable as the preceding models of the EY Series. Safety devices are also incorporated to assured added safety. 

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 aluminum casting. The intake and exhaust ports are 

located on one side of the cylinder, and are also inserted in- 

to the casing. 

The crankcase is separable on the output shaft side, where 

the main bearing cover is attached to it. (See Fig. 1 .) 

Fig. 1 

-4-

4-2 MAIN BEARING COVER 

B 

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 .) 

RING for CENTERING 

OIL GAUGE 

Fig. 2 Fig. 3 

4-3 CRANKSHAFT 

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.) 

INDUCTION HARDENING 

(PORTION of CRANKPIN) 

CRANK GEAR (PRESSURE-FIT) 

Fig. 4 

4-4 CONNECTING ROD and PISTON 

The connecting rod is forged of aluminum alloy, which itself 

serves as bearings at both the large and small ends. The 

large end has a built-in oil scraper for splashng 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.) 

SECOND RING 

Fig. 5 

-5-

4-5 CAMSHAFT 

Models EY3S-B, 3S-BS, EY40-B and 40-BS have intake and 

exhaust cams of forged carbon steel, which are fitted with a 

cam gear under pressure. The assembly serves as output shaft 

that is driven at one half the speed of the crankshaft. The 

cam gear has a governor fitted to it. 

Model EY35-D, 35-DS, EY40-D and 40-DS have a camshaft 

of special cast iron, which is integrally assembled with a cam 

gear. The two ends of the shaft serve as plain bearings so no 

ball bearings are used. 

(See Fig. 6.) 

Fig. 6 

0 

4-6 CYLINDER HEAD 

The cylinder head is an aluminum die casting, and forms a 

Ricardo type combustion chamber with ample area for high 

combustion effeciency. The spark plug is tilted for easy 

mounting of the fuel tank. 

(See Fig. 7.) 

Fig. 7 

4-7 VALVE ARRANGEMENT 

The exhaust valve is located upstream of the cooling air with 

the result that the exhaust valve is intensively cooled for 

improved engine durability. The inner side of the valve head 

is reinforced with hard alloy fused to it for added durability. 

(See Fig. 8.) 

. " 

. ". .._ _. 

Fig. 8 

-6-

4-8 GOVERNOR 

The governor is a centrifugal flyweight type which permits 

constant operation at the selected speed against load variations. 

(See Fig. 9.) 

4-9 BALANCER 

Fig. 9 

The balancer is assembled with the main bearing cover. Unbalanced 

moments of inertia generated in vertical and horizontal 

directions by the crankshaft, piston and connecting 

rod are balanced by the balancer whxh rotates at the same 

rate as the crankshaft in opposite direction thereto, thus reducing 

vibration due to unbalanced moments of inertia. 

(See Fig. 10.) 

4-10 DECOMPRESSION DEVICE 

Fig. 10 

The intake cam has a special profile and the intake valve is sligh .tly raised during the compression stroke to let a slight amou 

of compressed air out to make starting easy. (See Fig. 11 .) 

EXHAUST TAPPET IN TAPPET 

IN TAPPET 

'.O. SHAFT 

SIDE 

EXHAUST-CAM 

IN CAM 

DECOMP LIFT 

Fig. I 1 

-7-

4-11 COOLING DEVICE 

The cooling fan serving also as flywheel cools the cylinder and cylinder head by forced air cooling. An air guide plate and 

head cover are used to let the cooling air go through. 

The cooling fan employs curved blades so Types B and D have cooling fan parts special to their own. 

4-12 LUBRICATION 

". . 

The rotating and sliding parts are being lubricated by scooping 

and splashing the oil in the crankcase with the oil scraper 

attached to the connecting rod. 


OIL SCRAPER 

Fig. 72 

4-13 IGNITION DEVICE 

Models EY35 and EY40 have a flywheel magneto type ignition system (Fig. 13) with an ignition timing of 23" before TDC 

(Top Dead Center). The flywheel (also serving as fan) is fitted onto the crankshaft; and the 

ignition coil, contact breaker, 

and charging coil are directly assembled with the crankcase. An S.S.I. electronic system (Fig. 14) is also available in types, 

including a 1 SO-watt load type. 

The S.S.I. system, except the 150-watt type, electrically advances the ignition timing. The ignition timing after this advance 

is 23" before TDC. (See Figs. 13 and 14.) 

FLYWHEEL 

POINT COVER 

IGNITI~N COIL 

Fig. 13 

Fig. 14

4-14 CARBURETOR 

A horizontal draft carburetor is employed. It has been care- 

fully set after thorough tests to assure satisfactory start up, 

acceleration, fuel consumption, output performance etc. 

For construction and other details, refer to the Section 6. 

CARBURETOR (Construction, Disassembly 

blY 1. 


and Reassem- 

L , 

Fig. 15 

4-15 AIR CLEANER 

Cyclone type semi-wet double element air cleaner is used. 


Fig. 16 

4-16 DIODE RECTIFIER 

The engines with an electric starter have a diode rectifier 

which converts the alternating current generated by the 

charging coil into a direct current and charges the battery. 


Fig. 17 

-9-

4-17 SECTIONAL VIEW OF ENGINE 

/ 

RECOIL STARTER - I 

(OPTION) 

CRANKCASE 

BALANCER 

MODEL EY35D. 40D 

- 10 -

FUEL TANK CAP 

INTAKE & EXHAUST VALVE 

FUEL COCK 

BALANCER 

MODEL EY35D, 40D 

- 11 -

~ 

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 reassembled 

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

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

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

4) Carefully handle disassembled 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 Inspection Instruments. 

Part No. 

Tool 

Wse 

Applicable 

Model 

Shape 

EY10,13,14 

EY15,18,20 

2099500407 

Flywheel Puller 

(with bolt) 

For pulling off 

Flywheel 

EY25,27,33 

EY35,40,44 

EC05,07, 10 

ECf 7,25,37 

EYIQ, 13.14 

2079500307 

Valve Spring 

Retainer 

For mounting and 

dismounting Valve 

Spring Retainer 

and Retainer Lock 

EY15,18,20 

EY25,27,33 


EYlO, 13,14 

EY15,18,20 

EY25,27,33 

"20248 

riming Tester 

For adjusting 

timing 


EC03,04,05 

EC07,10,17 

EC25,37 

,"- 

- 12 -

5-3 HOW TO DISASSEMBLE 

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

Order 

Item 

Procedures 

Remarks 

Bolts, nuts, etc. used 

1 

Engine 

Drain engine oil. 

Drain plugs on both sides of the 

case 

Be careful not to lose the 

the gasket. 

Flange bolt 

2 

Fuel tank 

(1) Close the strainer cock. 

(2) Move the fuel pipe clamp (on 

strainer side) downward. 

(3) Remove the tank from tank 

bracket. 

8 mm (No.2) nut . . . 4 pcs. 

SpI-ing washer . . .4 pcs. 

3 

Tank bracket 

Remove tank bracket. 

10 mm flange nut . . . 4 pcs. 

(tightened together with 

cylinder head) 

4 

Air cleaner 

(1) Remove air cleaner cover and 

element. 

(2) Remove choke knob. 

(3) Remove the bottom plate of 

air cleaner. 

Swivel 

6 x 12 mm flange bolt 

. . . 2 pcs. 

5 

Muffler cover 

Remove muffler cover. 

6 x 8 (5T) Flange bolt 

* . . 4 pcs. 

6 

Muffler 

(1) Remove the flange portion 

of the muffler. 

(2) Remove the muffler bracket. 

8 mm brass nut . . . 2 pcs. 

8 x 16 (ST) Bolt & washer 

. . . 2 pcs., Washer . . . 1 pce 

7 

Carburetor 

Remove the carburetor. 

Be careful of the packing 

etc. 

Joint sheet, insulator, and 

then paper packing, in ths 

order from the engine side 

6 mm nut . . . 2 pcs. 

Spring washer . . . 2 pcs. 

Washer . . . 2 pcs. 

8 

Governor 

lever 

Remove the governor lever. 

Be careful of the position 

of the governor spring. 

6 mm special nut. . , 1 pce. 

Washer . . . 1 pce. 

6 x 25 (7T) bolt . . . 1 pce. 

Fig. 18 

- 13 -

I I I I I 

Order 

Item 

Procedures 

Remarks 


9 

Speed control 

Disassemble. 

Remember the assembling 

order of component parts. 


Circle clip ... 1 pce. 

8 mm butterfly nut. . . 1 pce. 

h 

- 

Order 

Item 

Fig. 19 

Remarks 


10 

Operation 

case 

(1) Disconnect the high voltage 

wire connecting the electric 

starter to the magnetic switch 

on the side of the switch. 

(2) Remove the bolts. (3 pcs.) 


Two of the three 6 x 8 (5T) 

flange bolts tighten the 

cylinder buffle and fan cover 

together. 

11 

Electric 

starter 

Remove electric starter. 

8 x 30 reamer bolt . . . 2 pcs. 

Spring washer . . . 2 pcs. 

Washer . . . 2 pcs. 

Fig. 20 

- 14-

Order 

- 

12 Fan cover 

- 

13 

14 

Item I Procedures I Remarks I Bolts, nuts, etc. used 

Starting pulley 

(1) Remove the fan cover. Removable by loosening 6 x 8 flange bolt ... 6 pcs. 

bolts 

(2) Remove the head cover. 

(3) Remove the cylinder buffle. 6 x 8 flange bolt ... 1 pce. 

Remove starting pulley. 

(See Fig. 21 .) 

8 x 12 (ST) bolt . . . 3 pcs. 

I Flywheel Remove flywheel. Be sure to use the fly- 18 mm nut . . . 1 pce. 

wheel puller. Do not Spring washer . .. 1 pce. 

- 

crankshaft. 

Fig. 21 Fig. 22 

b 

-- 15 -

Order 

15 

- 

16 

17 

Item 

Electric 

devices 

Cylinder head 

Tappet cover 

(breather 

plate) 

Procedures 

(1) Remove point cover. 

(2) Remove contact breaker. 

(3) Remove ignition coil and condenser. 

(1) Remove spark plug. 

(2) Remove cylinder head. 

Remove Tappet cover. 

Remarks 

Be careful of the primary 

lead connecting direction. 

Remove the lighting coil 

before disassembly. 


4 x 12 screw and washer 

. . . 2 pcs. 


. . . 1 pce. 


. . . 2 pcs. 

10 mm flange nut . . .8 pcs. 1 

Be Of the breather I 6 x 

valve mounting position 

14 flange bolt . . . 2 pcs. 

and the order of assembl- I 

ing packings. 


I 

I 

Intake and 

exhaust valves 

(1) Remove intake valve. 

(2) Remove exhaust valve. 

Intake and exhaust valve 

springs, retainers and retainer 

locks are common; 

but be sure to set up them 

on the original valves. 


Use valve spring retainers. 

Fig. 23 

Fig. 24 

- 16-

~ 

~~~ ~ ~ ~~~~~ 

~~ 

.2 

Irder I 

Item 

Procedures 

r 

Remarks I Bolts, nuts, etc. used 

19 Main bearing 

cover 

20 Camshaft 

I 

(1) Set the piston to the TDC, remove 

blind plug in the lower 

part of the front side of bearing 

cover, and insert the 4 mm 

stick. 

(2) Remove bolts. 

(3) Strike the side of main bearing 

cover with a plastic hammer 

or the like to remove the 

cover from crankcase. 

Remove camshaft. 


In case of Type B, be careful 

not to remove camshaft 

together. 

*Crankshaft and camshaft 

have adjusting shims. 

(TY Pe B) 

Camshaft can easily be 

pulled by hand. Be careful 

not to let the tappets 

drop. 1 

6 x 8 flange bolt . . . 1 pce. 

Gasket (aluminium) . . . 1 pce. 

8 x 35 (7T) set bolt . . . 8 pcs. 

Fig. 25 Fig. 26 

Order 

Item 

Procedures 

Remarks 


2 1 

Intake/exhaust 

tappets 

22 Connecting 

rod and piston 

23 Crankshaft 

~ ~~ 

Remove intake/exhaust tappets. 

(1) Return the lock washer. 

(2) Remove bolts. 

(3) Push the piston up out of 

the top of cylinder. 

Intake and exhaust tappets 

are the same, but be 

sure to intall them in their 

original positions because 

1 of the valve clearance. 

Hold crankshaft with hand. and I Be careful of oil seal on I 

gently tap the flywheel end. the 

crankcase magneto 

side. 

8 x 46 reamer bolt . ~ 

pcs. 

- 17 -

5-4 HOW TO REASSEMBLE 

5-4-1 PRECAUTION IN REASSEMBLY 

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 at- 

tention to the frictional noise and resistance. 

r' 

5-4-2 MEASURING CRANKCASE and CRANKSHAFT 

Bore the cylinder or take other steps as necessary to meet 

the following specifications before reassembling. 


E Y40 

29 +0.1 

I W (Crankshaft Pin Width) I 0 

Bore 

Piston Outside Diameter (In Skirt Thrust Direction) 

78 dia. 

40.019 

I 

84 dia. , +0.022 

I Piston to Cylinder at Piston Skirt Thrust Face I 

0.049L - 0.1 08L 1 0.049L - 0.1 11 L 

Piston Ring Gap (Top Ring - Second Ring) 

Piston Ring Side Clearance in Grooves 

(Top Ring - Second Ring) 

I 

0.1 L - 0.3L 

0.05 - 0.09 

Clearance between Connecting 

Rod Large End and Piston Pin 

Clearance between Connection 

Rod Small End and Piston Pin 

Clearance between Inside 

and Outside Diameter 

Side Clearance 

0.070 - 0.102L 

0.020L - 0.042L 

0.1 L - 0.4L 

Clearance between Piston Pin and Pinston Pin Hole 

0.1 1T - 0.01 1 L 

Fig. 27 

L: LOOSE 

- 18 -

5-4-3 ASSEMBLING ORDER and PRECAUTIONS 

1) Place the tappets into the crankcase. 

NOTE: The intake and exhaust tappets are the same, 

but mark them differently when disassembling 

because of different valve clearances; and 

fit them into their origianl place. Apply oil to 

the tappets beforehand. 

Assemble the crankshaft and camshaft at the same 

time. 

NOTE: The same timing mark as on the crankshaft 

side is punched on the crankshaft gear inward 

of the balancer gear as shown in Fig. 28. So, 

match these timing marks on the crankshaft 

and camshaft sides before installing these 

. . 

TIMING MARK ON CAMSHAFT SIDE 

(Punch 2 pcskl 

TIMING MARK ON CRANKSHA?? 

(Punch 1 pce.) 

Fig. 28 

shafts in the crankcase. 

3) Assemble the connecting rod with the piston. 

NOTE: The piston is not offset so a new piston does not require to be installed in a specific direction, but a used piston 

must be marked with a sign indicating its direction when disassembling so that it can be assembled again in the 

direction indicated. 

CAUTION: When inserting the piston pin and fitting the clip on, be careful not to damage the piston surface. 

4) Fit the piston rings on the piston. THRUST SIDE 

NOTE: Each piston ring must be installed upside up, 

that is, the puched mark at the open ends up. 

NOTE: The oil ring consists of three parts, that is, a 

spacer, lower rail, and upper rail. Fit them on UPPER RAIL LOWER RAIL 

in this order. The open ends of each ring must 

be as shown in Fig. 29. 

Fig. 29 

Fig. 30 Fig. 3 1 

ASSEMBLY TYPE OIL RING 

- 19-

~ MATCH 

5) Assemble the piston and connecting rod that were 

readied in Steps 3) and 4). 

NOTE: The symbol @FAN mark on the connecting 

rod must be on the magneto side. 

NOTE: Be careful of the match mark on the cap. If 

the match mark is at the correct position, the 

oil scraper should be on the main bearing cover 

side. 

NOTE: Tightening bolt . . . . . . . 8 x 46 (special) 

Tightening torque . . . 250 - 300 kg-cm 

Use new lock washers,and bend their edges 

securely. 

u__ 

Fig. 32 

Install the main bearing cover. 

NOTE: If the oil seal is damaged when the governor 

CRANKSHAFT SPACER 

\ 

yoke is installed, replace it with a new one. 

NOTE: Adjust the side clearance to anywhere between 

0.05 and 0.2 mm.Thesideclearance 

can be measured by measuring sizes A and B 

as shown in Fig. 33, and assume that the thickness 

of packing C is 0.25 mm when tightened. 

MAIN BEARING 

* The side clearance can also be measured as 

BALANCER 

shown in photos below. (Figs. 34 and 35) 

Fig. 33 

Fig. 34 

Fig. 35 

- 20 -

~~~~ ~ ~ 

NOTE: Check the main bearing cover joint for flaw, 

and correct if necessary. 

Fit the governor sleeve into the cam gear 

with new packing. 

* Move the piston up to TDC, insert the 4 mm 

stick into the main bearing cover, and fast- 

en the balancer as shown in Fig. 36. 

Tightening bolt . . . . . . . 8 x 35 (7T) 

Tightening torque . . .170 - 190 kg-cm 

* Insert the blind plug (6 x 8 flange bolt) into 

the balancer fixing hole with the aluminum 

gasket, and check if the crankshaft srnooth- 

ly runs. 

Fig. 36 

7) Install the intake and exhaust valves. 

* Intake and exhaust valve specifications are as follows: 

4O 

A.4 IF 

GUIDE 

VALVE and VALVE GUIDE CLEARANCE 

A-VALVE FACE ANGLE 

6-SEAT ANGLE 


E Y40 

C-GUIDE INSIDE DIA. 

D-VALVE STEM OUTSIDE DIA. 

MAXIMUM ALLOWABLE 

CLEARANCE 8ETWEEN C and D 

INTAKE 

INTAKE 

8dia. +0.036 

dia. -0.070 

-0.090 

0.030L - 0.091 L 

0.070L - 0.1 26L 

Fig. 37 

-21 -

.TAPPET CLEARANCE ADJUSTMENT 

Move the piston up to compression TDC, and adjust 

the tappet clearance as follows, using a grinder or the 

like. 

Clearance (Models EY35, EY40 intake and exhaust): 

0.13 - 0.17 mm when cold 

Fig. 38 

* Intake and exhaust valve installation 

Apply oil to the valve stems, and install the valves 

securely by using the special tool, valve spring retainer 

and pliers. (See Fig. 39.) 

After their installation, check the tappet clearance 

again. 

Fig. 39 

8) Install the breather plate and tappet cover. 

NOTE: Be careful of the gasket installing order (See 

Fig. 40.) and breather valve position. 

The breather valve must be on the intake valve 

side. 

6 x 14 flange bolt .......... 2 pcs. 

Fig. 40 

9) Install the cylinder head. 

NOTE: Replace the head gasket with a new one, and tighten the nuts uniformly with the specified torque. 

10 mm flange nut ........... 8 pa. 

Tightening torque ... 340 - 390 kg-cm 

- 22 -

10) Electrical installation 

* Install the ignition coil and capacitor. 

Screws: 6 x 25 screw and washer . . 2 pcs. each 

* Temporarily install the contact breaker. 

Screw: 4 x 8 screw and washer ... 1 pce. each 

CAUTION: Be careful of the location of the cord. 

rKER 

*IGNITION TIMING ADJUSTMENT 

Ignition timing ............ 23" before TDC 

Point gap ............... .0.35 k0.05 mm 

Adjusting method 

If the point surfaces are rough, smoothen them. Hold 

the top of the point cam on the crankshaft in contact 

with the heel of the contact breaker, and move the 

contact breaker itself until the correct point gap is ob- 

tained. The ignition timing of the engine depends on 

the point gap. If the gap is correctly adjusted, the igni- 

tion timing will be 23" before TDC. 

.IGNITION TIMING CHECK 

Use a timing tester, Part N0.M-20248 

Checking method 

As shown in Fig. 43, connect one of the 

other lead to the crankcase, switch the timing tester on, and hold the earphone 

Fig. 4 1 

Fig. 42 

leads of the timing tester to the primary wire of the ignition coil, and the 

close to the ear. Slowly turn the fly- 

wheel in normal direction (clockwise for Type D, or counterclockwise for Type B), and if the mark on the flywheel 

matches the M mark on the case when the buzzer sounds, it is the correct ignition timing. If the two marks do not 

agree, repeat the above mentioned adjustment. 

---" 

FLYWHEEL 

Fig. 43 Fig. 44 

- 23 -

*SPARK CHECK 

* Clean the point surfaces of oil with paper or the like, and temporarily install the flywheel. 

* Hold the high-voltage wire with hand so its end is about 5 mm away from the case, and turn the flywheel in normal 

direction. 

* Check that a spark is generated when the M mark on the flywheel passes the M mark on the case. 

* Install the point cover. 

4 x 12 screw and washer ...... 2 PCS. 

11) Install the flywheel. 

NOTE: Before installing the flywheef, clean the crankshaft and the tapered part of the flywheel of oil. 

16mmnut ................ 1 pce. 

Spring washer .............. 1 pce. 

Washer. .................. 1 pce. 

Tightening torque .. .800 - 1000 kg-cm 

12) Install the starter pulley. 

8 x 12 bolt (ST) ............ 3 pcs. 

13) Install the fan cover and head cover cylinder buffle. 

NOTE: Before installing the fan cover, first install the head cover on the cylinder head. Also install the muffler brack- 

et in place at the same time. 

6 x 8 flange bolt ............ 7 pcs.' 

14) Install the recoil starter 

NOTE: Pulling direction may vary with machine make. 

15) Install the carburetor. 

6 x 8 flange bolt ............ 4 pcs. 

NOTE: Install the carburetor with the joint sheet, insulator, and paper packing in this order. 

6 mm nut ................. 2 pcs. 

Spring washer .............. 2 pcs. 

Washer. .................. 2 pcs. 

16) Install the speed control and governor lever according 

to the arrangement of parts shown in Fig. 47. Hook 

the governor spring at the proper hole. 

8 mm wing nut ............. 1 pce. 

Clip.. ................... 1 pce. 

0 

Fig. 45 

- 24 -

.GOVERNOR SETTING METHOD 

* Set the speed control lever to the high-speed posi- 

tion, and fasten it there with the 

wing nut. (The 

governor spring is in.) 

* Check that the carburetor and throttle valve are 

fully open. 

* Turn the governor shaft counterclockwise, and 

fasten the governor lever. (See Fig. 46.) 

Install the starter motor. 

8 x 30 reamer bolt ........... 2 pcs. 

Spring washer .............. 2 PcS. 

Washer. .................. 2 pes. 

Install the operation case. (with the electric starter) 

Fig. 46 

6 x 8 flange bolt (5T) ......... 3 pcs. 

* Two of the three flange bolts tighten the case together with the cylinder buffle and fan cover. 

* Properly wire as shown in the wiring diagrams (Pages 34 and 35). 

Install the muffler. 

NOTE: The muffler gasket must be placed in 'the correct direction. (Non-symmetric direction) 

8m brass nut ............... 2 pcs. 

8 x 16 bolt (for bracket) ....... 2 pcs. 

Washer. .................. 1 pce. 

Install the muffler cover. 

6 x 8 flange bolt (5T) ......... 4 pcs. 

Install the air cleaner. 

NOTE: Make sure that the tip of the breather pipe out of the tappet cover is clear off the element retainer. 

6 x 12 flange bolt ........... 2 pcs. 

After mounting the cleaner bottom plate, install the choke knob, element retainer, element and cover in ths order. 

Install the tank bracket. 

10 mm flange nut ........... 4 pcs. 

(also for cylinder head) 

Install the fuel tank. 

8 mm No.2 nut ............. 4 pcs. 

Spring washer .............. 4 pcs. 

Connect the fuel pipe. 

Clamp the pipe securely. 

Supply 1.2 liter engine oil. 

-25 -

6, CARBURETOR 

SPECIFICATION 

I 


I 

E Y40 

Model 

Part No. 

Main Jet 

Main Air Jet 

Pilot Jet 

6 -1 OPERATION and CONSTRUCTION 

#107.5 

BV26-20 BV26-19 

2246230100 2236230100 

#112.5 

$1.2 $1.5 

#57.5 #55 

Throttle Valve #135 #150 

Pilot Screw 

1 I 1 turn 

(Return) 

A 

PI LOT 

FUEL 

NEEDLE VALVE 

FLOAT 

FLOAT CHAMBER 

W 

Fig. 48 

- 26 -

6-1 -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. 

6-1 -2 PI LOT 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 outllet and the by-pass. 

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

6-1-3 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. 

6-1 -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 pres- 

sure applied to the main nozzle increases and draws much fuel accordingly; thus easily start up the engine. 

' 

6-2 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 ah or fuel passage in jets, or fuel level variations. In order to assure proper flow of air and fuel, the car; 

buretor must be kept clean at all times. The carburetor disassembly and reassembly procedures are as follows: (See Fig. 49.) 

6-2-1 THROTTLE SYSTEM 

1) Remove the Phdlips screw (I) and throttle valve (2), and pull out the throttle shaft (3). 

2) The spring (5) can be taken out by removing the throttle stop screw (4). 

*Be careful of the direction of the throttle valve. 

The circumference of the throttle valve is aslant. Install the valve so the punched mark on the valve can be seen on the 

left. 

6-2-2 CHOKE SYSTEM 

I) Remove the Phillips screw (6) and choke valve (7), and pull out the choke shaft (8). Stop ring (9) can not be removed. 

2) When reassembling the choke shaft, make sure that the cutout in the choke valve faces the main air jet. 

6-2-3 PILOT SYSTEM 

I) Remove the pilot jet (1 0), using correct tool to avoid damage to it. 

2) Remove pilot screw (1 1) and spring (1 2). 

3) Reassembly 

*Tighten the pilot jet securely. Otherwise, the fuel may leak, causing engine malfunction. 

*If the tapered part of the pilot screw is out of shape, replace it with a new one. 

- 27 -

~ 

1 

6-2-4 MAIN SYSTEM 

1) Remove the bolt (13) and take out float chamber 

body (15). 

2) Remove the main jet (17) and main nozzle (18), using 

correct tool to avoid damage to it, 

3) Reassembly 

Fasten the main jet securely to the body. Otherwise, 

the fuel may become too rich and cause engine malfunction. 

6-2 -5 FLOAT SYSTEM 

When removing the needle valve (21) and float (20), gently 

tap the reverse side using the rod more slender than the 

float pin (19) and remove because the float pin is calked to 

the carburetor body. 

*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. 

Fully tighten the pilot screw and then loosen it counterclockwise 

by one turn for Model EY35, or one 

turn and a half for Model EY40. When fully closing 

the pilot screw, do not tighten it too hard. Otherwise, 

the needle at the tip might become damaged. 

Turn the throttle stop screw clockwise to a normal 

idling speed of 1200 rpm. 

Make a final adjustment when the engine is in normal 

operating condition at normal temperature with the correct 

I A ‘17 

-18 

19 

Fig. 49 

air cleaner mounted. 

7. 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. 

Thl e recommended break-in schedule is shown below. 

LOAD 

EY35 EY 40 

NO LOAD 

SPEED 

2,500 rprn 

TIME 

10 minutes 

NO LOAD 

3,000 rpm 

10 minutes 

NO LOAD 

3,600 rprn 

10 minutes 

3.5 HP 

4.0 HP 

7.0 HP I 8.0 HP ~ 

3,600 rpm 

30 minutes 

3,600 rpm I 60 minutes 1 

- 28 -

8. ROBIN SOLID STATE IGNITION ENGINE (OPTION) 

8-1 FEATURES 

The S.S.I. system is free of the weak points of the conventional point type ignition system, that is, ignition failure due to a 

dirty or burnt contact point, oxidation during long storage,and mechanical wear,and featuresmaintenance-free performance, 

proper sparking, and freedom from the ill effects of water, oil dust, and moisture. 

8-2 BASIC CIRCUIT and OPERATING THEORY of 

S.S. I. SYSTEM 

1) As the flywheel and magneto rotate, a voltage is in- 

duced in the exciter coil, and flows through the pri- 

mary wire to the transistor base. A 

2) At the same time, the transistor is energized to form a 

circuit between the exciter coil and the transistor. B 

3) At the ignition time, electric power flows from the 

pulser coil to the SCR gate to energize the SCR. C 

Thus the current flowing to the transistor is cut off, 

and the exciter current suddenly rushes to the prima- 

ry side of the ignition coil. D Thus, a high voltage is 

generated on the secondary side of the ignition coil to 

produce a spark in the spark plug. E 

L 

IGNITION UNIT 

Fig. 50 

"-1 

IGNITION COIL 

8-3 CHECKING IGNITION UNIT with TESTER 

The ignition unit can be checked with an ordinary circuit 

tester. 

Checkit as shown in the table at right, and if the test results 

are as specified, the ignition unit is in normal condition. If 

any of the test results is not satisfactory, replace the whole 

ignition unit. 

NOTE: Use a circuit tester, not a megger or other 

tester that requires high ovltage. ON in the 

table indicates the forward characteristic of 

the diode, and if the tester pointer moves to 

a certain extent, it is good. 

OFF in the table indicates ma. 

8-4 MEASURING RESISTANCES of EXCITER COIL and PULSER COIL 

Connect (+) terminal of tester. 

I 

Exciter Coil 

Pulser Coil 

A - t B 

A + B 

STD 

150W 

0.97Q * 20% 

4.5R * 20% 

66Q * 20% 

t 

Fig. 51 

* Values in the table above apply where ambient temperature 20°C. is 

- 29 -

9. 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 dif- 

ficult, 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: 

9-1 STARTING DIFFICULTIES 

9-1 -1 FUEL SYSTEM 

NO gasoline in th fuel tank; or the fuel cock is closed. 

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

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

Inferior grade gasoline or poor quality gasoline is not gasfied enough to produce the correct fuel-air mixture. 

The carburetor needle 

carburetor when the engine is idling. (Overflow) 

valve is held open by dirt or gum. This trouble can be detected as the fuel flows out of the 

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

of the like. 

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 turn the starting pulley 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. 

9-1-2 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 or loose cylinder head. A similar hissing noise is produced during compression stroke. 

4) Incorrect Tappet Clearance 

If the correct compression is not obtained even after remedying the above, disassemble the engine and check further 

as follows: 

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

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. 

- 30 -

9-1-3 ELECTRICAL SYSTEM 

Check the following for lack of sparks. 

Leads of the ignition coil, spark plug or contact breaker disconnected. 

Ignition coil damaged and shorted. 

Spark plug cable wet or soaked with oil. 

Spark plug dirty or wet. 

Spark plug electrode gap incorrect. 

Spark plug electrodes in contact with each other. 

Contact breaker points pitted or fused. 

Breaker arm stuck. 

Condenser leaking or grounded. 

Incorrect spark timing. 

ENGINE MISFIRES 

0 

9-3 ENGINE STOPS 

1) 

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

Ignition cable worn and leaking. 

Sparks weak. 

Ignition wire connections loose. 

Pitted or worn breaker points. 

Water in gasoline. 

Insufficient compression. 

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

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

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

Air vent hole in the fuel tank ca plugged. 

Bearing p.arts seized due to lack of oil. 

Magneto or ignition coil faulty. 

9-4 

ENGINE OVERHEAT 

Crankcase oil level low. Add oil immediately. 

Spark timing incorrect. 

Low grade gasoline is used, or engine is overloaded. 

Cooling air circulation restricted. 

Cooling air party misdirected causes loss of cooling efficiency. 

Cylinder head cooling fins clogged up with dirt. 

Engine operated in an enclosed space without fresh supply of cooling air. 

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

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

- 31 -

ENGINE KNOCKS 

Low-quality gasoline. 

Engine operating under heavy load at low speed. 

Carbon or lead deposits in the cylinder head. 

Spark timing incorrect. 

Loose connecting rod bearing due to wear. 

Loose piston pin due to wear. 

Causes of engine overheat. 

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. 

- 32 -

10. INSTALLATION 

Engine life, ease of maintenance and inspection, frequency of checks and repairs, and operating cost all depend on the way 

in whlch the engine is installed. Carefully observe the following instructions for installing the engine. 

10-1 INSTALLING 

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

and the method 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 and breaker can easily be checked, the air cleaner can easily be serviced, and that the oil can easily be discharged. 

10-2 VENTILATION 

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

In cases 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 the 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. 

10-3 EXHAUST GAS DISCHARGE 

Exhaust gas is 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 in- 

crease in proportion to exhaust pipe length. 

* Exhaust pipe: Less than 3 m long, pipe inside diameter 30 mm, 

Less than 5 m long, pipe inside diameter 33 mm. 

* Put safety covers over the exhaust pipe, muffler, etc. 

10-4 FUEL STSTEM 

If the fuel tank is removed from the engine in mounting the engine in a machine, install the fuel tank back so its bottom is 

5 cm to 50 cm above the fuel joint of the carburetor. If the fuel tank is installed too low, the fuel will not be supplied. If 

the fuel tank is too high, on the other hand, it can cause the carburetor to overflow. 

Be careful of heat conduction, pipe size, bends, and leaks from the joints in piping and make the fuel pipe as short as possible 

to prevent air and vapor from being trapped. The standard fuel pipe diameter is 4 to 5 mm. 

10-5 POWER TRANSMISSION to DRIVEN MACHINES 

10-5-1 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 the like. 

- 33 -

10-5-2 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. 

10-6 WIRING 

Models EY35 and EY40 are available in types that have the ignition and starting systems shown in the wiring diagrams 

below. 

The parts indicated by dotted lines in the diagram are not normally supplied with the engine. 

[RECOIL STARTER TYPE and LIGHTING COIL] 

Note: Standard type is not equipped 

with the lighting coil. 

MAGNETO 

STOP BUTTON 

- - - - - - - - - 1 

E 

SPARK PLUG 

Green/Yellow 

BUZZER 

Fig. 52 

[ELECTRIC STARTER TYPE] 

MAGNETO 

KEY SWITCH 

ELECTRIC STARTER MAGNETIC SWITCH 

Fig. 53 

[S.S.I. with RECOIL STARTER and LIGHTING COIL] 

MAGNETO 

1 

SPARK PL .UG 

STOP BUTTON 

BUZZER 

6V8W @* QLAMP 12V15W 

I 

J, 

Fig. 54 

- 34 -

[S.S.I. with ELECTRIC STARTER] 

KEY SWITCH 

BATTERY 

12W24AH 

[S.S.I. 15OW with ELECTRIC STARTER] 

EXCITER COIL 

RedIWhite 

CHARGING COIL 

12V24AH 

- ""_ ""-I 

[ A E 

Black/White 

Red 

LZRIC STARTER 

Fig. 56 

* The symbols shown in the wiring diagrams above signify the following. 

"""- Not mounted on the engine 

-- JIS CB104 jack 

-D JIS CA104 plug 

@ JIS LA104 or LA108 plate terminal 

* In the wiring diagram showing the circuit with a recoil, the ignition coil is optional, and therefore is not supplied on 

the standard models. 

- 35 -

10-7 VINYL-INSULATED WIRE 

Recent engine sets become complex, and an increasing number of them are remote-controlled. 

When designing or repairing such machines, special care must be taken in selecting their wire. Select the correct wire from 

the table below by considering the following. 

FACTORS TO BE CONSIDERED 

* Amperage 

* Current flowing time (continuous, intermittent) 

* Wire length 

* Mechanical strength of wire against vibration 

* Wire size versus resistance 

Size (mm2 I 

0.50 

0.85 

1.25 

2.0 

3 .O 

5 .O 

8.0 

15.0 

20.0 

30 .O 

No. of conductors/ 

conductor diameter (mml 

7r0.32 

11r0.32 

1 6r0.3 2 

2610.32 

41 10.32 

6510.32 

5010.45 

8410.45 

4 1 10.80 

70f0.80 

Resistor (Wml 2OoC Albwable curre1 

(I 

0.03250 9 

0.02050 

0.01410 

12 

1.5 

0.00867 

20 

0.00550 

27 

0.00374 

37 

0.00228 

47 

0.00136 

59 

0.00087 

84 

0.00051 

120 

* Electrical resistance increases with wire length, and decreases as conductor diameter increases. Resistance also varies 

with material even if size and length are the same. 

* Nominal size means the nominal area of steel wire expressed by 00 square (SQ). 

- 36 -

11. CHECKS and CORRECTIONS 

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

table applies whenever the engines are repaired. It is important for the servicemen to be familiar with the contents of tlus 

table. Correct maintenance is recommended by observing the correction standardspecified. 

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

1) Correction 

Repair, adjustment oreplacement of any engine parts. 

2) 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. 

3) Use Limit 

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

4) Standard Dimensions 

The design dimensions of new parts minus tolerance. 

5) Correction Tolerance 

Tolerance on the dimensions of engine parts refinished or adjusted. 

- 37 -

12. TABLES OF CORRECTION STANDARDS 

ITEM 

Flatness of cylinder 

head 

Bore 

ENGINE 

MODEL 





STANDARD 

SIZE 

S.T.D. 78 dia. 

84 dia. 

T T - 

CORRECTION 

CORRECTION 

METHOD 

USE 

TOLERANCE LIMIT LIMIT 

REMARKS TOOL 

Surface 

0.05 0.1 5 plate, Correct 

Feeler 

Dif. between 

max. & min. 

+0.019 0 

0.1 5 0.65 

Roundness 



0.01 Boring 

Cylindricity 

Valve seat contact 

width 

EY 35 




0.01 5 

- 

1.2-1.5 2.5 

Correct 

Valve guide I.D. 

EY 35 


8 dia. +0.036 0.1 5 0.1 5 

0 

At middle 

portion 

Replace 

O.D. at skirt, in 

thrust direction 

(incl. over size) 

B 0.25 

C 0.5 

Width of ring 

groove 





S.T.D. 77.951 dia. 

B 78.201 dia. 

C 73.451 dia. 0 

S.T.D.83.951 dia. -0.04 

B 84.201 dia. 

C 84.451 dia. 

+0.06 - 

Top, 2nd 2 Top +0.04 

Oil 4 

oil +0.055 - 

+0.2 

- 0.1 

- 

0.1 5 

-0.1 

0.1 5 

Micrometer 

Vernier 

caliwrs 

Replace 

Replace 

Piston pin hole 

Clearance between 

piston and cylinder 


pisition ring and 

ring groove 







20 dia. +0.002 

-0.01 1 

0.035 0.035 

0.048 - 

0.108 

0.048 - 

0.025 0.025 

0.1 11 

Top 0.05 - 

2nd 0.09 

Max. cylinder 

dia. and 

piston dia. 

at skert in 

thrust direction 

Cylinder 

gauge, 

Micrometer 

Replace 

0.1 5 0.1 5 Replace 

Fit between piston 

and piston pin 



0.011 T 

0.011 L 

Cylinder 

gauge, 

Micrometer 

Ring gap 



TOP 

0.1 - 0.3 

2nd 

Oil 0.2 - 0.9 

1.5 

- 

1.5 

Replace 

Ring width 



Top.2nd 2 

Oil 4 

TOP -0.01 

2nd -0.03 

- 0.1 

-0.1 

Mircrometer 

- 

- 38 -

~~~~ ~ 

I."&, 

ITEM 

1 ENGINE1 STANDARD 1 CORRECTION 

Piston pin 0. D. 

Large end I. D 

rod large end I.D. 

and crankpin 

Small end I.D. 

a :L."-- 

V 

E 

b 

1 

parallelism 

Large end side 

clearance 

Parallelism between 

large end and 

Distance between 

large end and 

small end bores 

Crankpin O.D. 

Crankpin O.D. 

roundness 

cylindricity 

Crankpin O.D. 

Crankpin O.D. 

USE 1 REMARKS 

1 

MODEL SIZE 

LIMIT TOLERANCE 

LIMIT 

t 

+ 

Micro- 

-0.03 I 

meter 

1 

Cylinder 


34 dia. +0.016 - 0 0.1 


gauge 

Oql I 

Cylinder 

0.2 

gauge, 

EY35 EY40 I 1 

Micro- 

I 1 

meter 

EY15 +0.033 

Cylinder 

20 dia. +o.02 0.08 0.08 

gauge 

I 

I 

Cylinder 

EY15 0.02 - 0.042 0.12 

gauge, 

0.12 

EY20 

Micro- 

1 

meter 

Feeler 

0.1 - 0.4 1.0 

gauge 

Test bar 

0.1 

gauge 

1 

I 



1 EY15 

EY20 

EY15 

EY20 

I 

EY 20 

EY15 

Drive 5. 25 dia. 

I 

-0.070 - -0.080 0.1 5 

Less than 0.005 



0'15 I 

0.5 I 

Test bar 

and Micrometer 

Micrometer 

Micrometer 

Micrometer 

Dial 

gauge 

METHOD 

CORRECTION 

Replace 

Replace 

Replace 

Replace 

Replace 

Re-machine 

or Replace 

Re-machine 

or Replace 

Replace 

Re-machine 

or Replace 

Re-machine 

or Replace 

Re-machine 

or Replace 

Re-machine 

or Replace 

I 

Crankshaft 

journal O.D. 

Cam lobe height 


Mag. s. 25 dia. 

-0.003 

Drive,s. 25 dia. -0.014 

Mag. s. 25 dia. 

Intake 36 

Exhaust 35.5 

to.1 -0.25 

Micrometer 

I 

Micrometer 

-0.25 

Replace 

Replace 

EY35B 

EY35D 

Drive S. 35 dia. 

-0.003 

-0.014 

-0.003 

Mag. S. 25 dia. -0.012 

-0.01 

,. 

- 0.05 

n. P 


6 

0.05 

-0.027 

Mag. S. 17 dia. -0.016 

-0.01 7 

0.05 

Micrometer 

Replace 

- 39 -

ITEM 

1 

4- 

.4- 

5 Journal OD. 

Valve stem O.D. 

EY4OB 

EY40D 



1 

1 EY35 


TOOL 

CORRECTIOP 

LIMIT 1 REMARKS 1 METHOD 

i 

-0.003 


-0.014 

-0.003 

Mag. S. 25 dia. 

-0.01 2 


-0.016 

-0.027 

Micro- 

0.05 0.05 

Replace 

Meter 

-0.027 

Vernier 

46 -1.5 -1.5 

Replace 

calipers 

Exhaust 8 dia. 

- 0.030 

-0.055 

-0.070 

-0.15 

!Square 

feeler 

I 

Qawe 

Micro. 

meter 

Replace 

Replace 


EY35 Intake 0.030-0.091 

EY40 Exhaust 0.070-0.126 

0.3 

0.3 At middle 

Replace 

w 


4 

= I 

I 

groove and retainer 

Stem end length 

Total length 

1 1 EY35 


E 1-Clearance between EY35 1 

I stem and guide 


5.3 

Pilot screw 

unscrew EY40 I 1% 

7 


EY40 1 

Spark plug 

I 

Point opening 


0.04-0.1 5 

-0.5 

-L 

0.025-0.062 0.2 

Vernier 

-0.5 I 

EY35 I 1 I I 

I( 

+1/4 

I 

B-6HS 

I 



0.6 - 0.7 I 1.0 

EY35 i 3O f 5" 

23'before T.D.C. . 


EY35 0.35 f 0.05 f 0.1 

calipers 

Vernier 

calipers 

Cylinder 

gauge & 

Micrometer 

Timing 

tester 

Correct 

Replace 

Replace 

Replace 

Replace 

Adjust or 

replace 

Adjust 

Adjust 

-40 -

~~~ 

ITEM 

MODEL 

Max. Output 



8.514000 

1 0.0/3,600 

Below 1 10% of rated output 

Continuous Rated 

output 



7.013600 

8.013600 

I 

ITEM 

MODEL 

literlhr 

CORRECTION PRECISENESS 

REMARKS 

Fuel Consumption 

EY35 2.9 

Up 135% of standard consumption 

EY40 3.5 

At continuous rated output 

1 I I 1 

ITEM 

MODEL 

cc/hr 

USE LIMIT cc/hr 

REMARKS 

Lubricant 

Consumption 

EY35 25 - 30 

60 

EY40 30 - 40 

80 

- 

ITEM 

MODEL 

liter 

REMARKS 

Fixed quantity 

of Lubricant 



1.2 

ITEM 

MODEL 

liter 

REMARKS 

Use the class SC or higher grade Engine Oil 

Winter (lower than 0°C) SAE 1 OW-30 

Spring and Autumn SAE #20 

Summer SAE #30 

I I I 

1 

ITEM FREQUENCY 

OF OIL CHANGE MODEL 

Oil Change 



First time: Change oil after 20 hours operation. 

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

ITEM 

I 

MODEL 


I 

kg/cm'/rpm 

CORRECTION LIMIT 

TOOL 

REMARKS 

I I 

I 

1 

- 41 -

- 

ITEM 

MODEL 

rpm 

TOOL 

REMARKS 

,- 

Min. accelerating 

revolution 

Crankshaft 

- 

r 

ITEM I MODEL I kgcm 

Cylinder head 

clamp nuts 



340- 390 

T 

ft-lb 

TOOL 

REMARKS 

24.6-28.3 Torque wrench 

Connecting rod 

bolts 



250 - 300 

18-21.7 Torque wrench 

Magneto 

nuts 

1 

clamp EY35 

EY40 1 

800-1000 


Main bearing cover 

bolts 


170-190 


Spark plug 

EY 35 


260 - 290 

18.8-21 Torque wrench 

-42 -

13. 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. 

13-1 DAILY CHECKS and MAINTENANCE 

Checks and maintenance I 

Reasons for requiring them 

Remove dust from whatever parts which 

accumulated dust. 

Check external fuel leakage. If any, retighten or 

replace. 

The governor linkage is especially susceptible to dust. 

Not only wasteful but also dangerous 

Check screw tightening. If any loose one is found, 

I re-tighten. 1 accidents. 

Check oil level in crankcase and add up as necessary. 

I fail. 

Loose screws and nuts will result in vibration 

If the engine is operated without sufficient oil, it will 

13-2 EVERY 20 HOURS CHECKS and MAINTENANCE 

Checks and maintenance Reasons for requiring them 1 

I Change crankcase oil. 1 TO remove run-in wear particles I 

13-3 EVERY 50 HOURS (10 DAYS) CHECK and MAINTENANCE 

Checks and maintenance Reasons 

for requiring them 

Change crankcase oil. 

I 

Contaminated oil accelerates wear. 

~____ 

Clogged air cleaner harms engine operation. 

1 Check spark plug. If contaminated, wash in 1 Output power is reduced and starting 

gasoline or polish with emery paper. 

is made difficult. 

13-4 EVERY 100- 200 HOURS (MONTHLY) CHECKS and MAINTENANCE 

I Checks and maintenance Reasons for requiring them 1 

Clean fuel filter and fuel tank. 

The engine will be out of order. 

Clean contact breaker points. 

The engine output drops. 

-43 -

13-5 EVER'.' 502 - 600 HOURS (SEMIANNUAL) CHECKS and MAINTENANCE 

Checks and maintenance 

Remove cylinder head and remove carbon 

deposit. 


The engine will be out of order. 

Disassemble and clean carburetor. 

13-6 EVERY 1000 HOURS (YEARLY) CHECKSand MAINTENANCE 

I 

Checks and maintenance 

I 


Perform overhauls, clean, correct or replace 

parts. 

The engine output drops and become out of order. 

Change piston rings. 

I Replace fuel pipe once a year. 1 To prevent from danger caused the fuel by leakage. 

13-7 PREPARATION for LONG ABEYANCE 

1) Perform the above 13- 1 and 13-2 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. 

- 44"

Industrial 

Engines

EY35, EY40 - Small Engine Discount

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