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Subaru Robin EY15, EY20, EY28 Engine Full Service & Repair Manual
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ROBIN AMERICA, INC.
ROBIN TO WISCONSIN ROBIN
ENGINE MODEL CROSS REFERENCE LIST
ROBIN
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
WISCONSIN ROBIN
SIDE VALVE
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
OVERHEAD VALVE
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
TWO CYCLE
WT1-125V
DIESEL
WRD 1-230
WRD 1-270
-1-300
WRD1-350
WRD1-410

CONTENTS
Section Title Page
1 . SPECIFICATIONS ...........................................
2 . PERFORMANCE ...........................................
2- 1 Maximum Output .......................................
2-2 Continuous Rated Output .................................
2-3 Maximum Torque .......................................
3 . FEATURES ...............................................
4 . GENERAL DESCRIPTION of ENGINE CONSTRUCTION ...............
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 .....................................
Main Bearing Cover ......................................
Crankshaft ...........................................
ConnectingRodandPiston ................................
Camshaft ............................................
Valve Arrangement ......................................
Cylinder Head .........................................
Governor ............................................
Cooling ..............................................
Lubrication ...........................................
Ignition .............................................
Carburetor ...........................................
Air Cleaner ...........................................
Sectional View of Engine ..................................
5 . DISASSEMBLY and REASSEMBLY ...............................
5-1 Preparation and Suggestion .................................
5-2 Special Tools ..........................................
5-3 Haw To Disassemble .....................................
5-4 How To Reassemble .....................................
6 . MAGNETO ...............................................
6-1 Magneto .............................................
6-2 Breaker Point Adjustment .................................
6-3 Timing Adjustment for EY15. EY20 Point Type Ignition System ........
6-4 Magneto Trouble Shooting .................................
6-5 Solid State Ignition ......................................
7 . GOVERNORADJUSTMENT ...................................
8 . CARBURETOR ............................................
8- 1 Operation and Construation ................................
8-2 Disassembly and Reassembly ...............................
9 . BREAK-IN OPERATION Of REASSEMBLED ENGINE ................
1
3
4
4
4
5
5
6
6
7
7
8
8
8
9
9
10
18
18
18
20
27
37
37
37
38
39
39
40
42
42
43
45

Section Title pese
10 . ROBIN SOLID STATE IGNITION ENGINE (T.I.C. and P.I.T.) ............ 46
10-1 Features ............................................. 46
10-2 Basic Theory of T . I.C. ................................... 46
10-3 Basic Theory of P . I.T. ................................... 46
11 . TROUBLE SHOOTING ....................................... 47
11 . 1 Starting Difficulties ...................................... 47
11 -2 Engine Misfires ......................................... 48
1 1-3 Engine Stops .......................................... 48
11 -4 Engine Overheats ....................................... 48
11 -6 Engine Backfires through Carburetor .......................... 49
12 . INSTALLATION ............................................ 50
12-1 Installing ............................................. 50
12-2 Ventilation ........................................... 50
12-3 Exhaust Gas Discharge .................................... 50
12-4 Power Transmission to Driven Machines ........................ 50
12-5 Wiring .............................................. 51
13 . ELECTRIC STARTING MOTOR (Option) .......................... 53
13- 1 Specifications ......................................... 53
13-2 Operation ............................................ 53
11-5 Engine Knocks ......................................... 49
14 . RECOIL STARTER DISASSEMBLY and REASSEMBLY ................ 54
14-1 How To Disassemble (Type D) .............................. 54
14-2 How To Reassemble (Type D) ............................... 55
14-3 Check Items after Reassembly ............................... 57
14-4 How To Do in Such Cases! ................................. 57
15 . CHECKS and CORRECTIONS ................................... 58
16 . TABLE of CORRECTION STANDARDS ........................... 59
17 . MAINTENANCE and STORING .................................
17-1 Daily Checks and Maintenance ..............................
17-2 Every 20 Hours Checks and Maintenance .......................
17-3 Every 50 Hours Checks and Maintenance .......................
17-4 Every 100 - 200 Hours (Monthly) Checks and Maintenance ...........
17-5 Every 500 - 600 Hours (Semiannual) Checksand Maintenance .........
17-6 Every 1000 Hours (Yearly) ChecksandMaintenance ................
17- 7 Preparation for Long Abeyance ..............................
65
65
65
65
65
66
66
66
.


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 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 sudrpower as developed by that engine when running continuously at an opti-
mum speed, and most favorable from the viewpoint of engine life and fuel consumption ratio, with the governor in opera-
tion. 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.
23 MAXIMUM TORQUE
These mean the maximum torque of the output shaft and fuel consumption ratio at the maximum output of an engine.
PERFORMANCE CURVES
MODEL EY15D, 15B
( 1 for B type
4
Ma;. Torque ~ 0.7
-
I I 7 0.6
HP
t i i
I \ I I I I I I
I
2000 3000 4000
(1 000) (1 500) (20001
r.p.m.
Revolution
kg-m
-2-

PERFORMANCE CURVES
MODEL EYZOD
5
Max. Toraue 1 .o
4
3
HP
L .
B
2 2
w
r
1
2000 3000 4000
Revolution
r.p.m.
2000
(1 000)
PERFORMANCE CURVES
MODEL EY28D, 288
I ) for B tvm
3000
( 15001
Revolution
r.p.rn.
4000
I20001
3. FEATURES
1. Compact, lightweight, durable, powerful 4-cycle air-cooled engine embodying ingenious design techques and skilful
workmanship.
2. Simple construction, smart appearance, maximum easiness of start owing to automatic decompression device
3. Pointless Solid State ignition system is newly adopted for preventing poor igniting as option.
4. Reliable prime mover for variety of purposes with smooth speed control by agovernor under varying load conditions.
5. Economical because fuel consumption is very low.
6. Great ve:satility in installation through a 360" belt extension possibihty and a two-side oil fill and drain arrangement.
-3-

4. GENERAL DESCRIPTION of ENGINE CONSTRUCTION
4-1 CYLINDER, CRANKCASE
The cylinder and crankcase are single piece aluminum die
casting. The c y h d e r liner, made of special cast iron, is built
into the alminum casting. The intake and exhaust ports are
located on one side of the cyhder, 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 shaftside of the crankcase so that the inside
of the engine can readily be checked by simplyremoving the cover. It is provided with a flange and boss for directly mount-
ing machmes, such as generators and pumps.
Two oil gauges also serving as oil filler caps can be mounted. (See Fig. 2 and Fig. 3.)
The EY 15B engine has 2 chain guides and a built-in shelter plate to prevent oil from being stirred by the governor gear
(See Fig. 4.)
Ring for Centering
/
Oil Gauge Oil Gauge
Fig. 2
I
Governor Gear
Fig. 3
Chain Guide
- Shelter Plate
1
Fig. 4 (E Y 15B)
-4-

4-3 CRANKSHAFT
The crankshaft is forged of carbon steel, and the crankpin is induction-hardened. It has a crank gear premred-fitted on the
output end. (See Fig. 5.).
"he EY 15B type has a built-in drive sprocket. (See Fig. 6.)
Induction Hardening
(Portion of Crankpin)
Crank Gear
(Pressure-Fit)
Drive Sprocket
-
Fig. 5
Fig. 6 (E Y 158)
4-4 CONNECTING ROD, PISTON and PISTON RING
The connecting rod is forged of aluminum alloy, which it-
self serves as bearings at both the large and small ends. The
large end has a built-in oil scraper for splashing the lubri-
cating oil.
The piston is cast of aluminum alloy, and has grooves for
receiving two compression rings and one oil ring.
(See Fig. 7.)
PISTON RINGS for EY28 ENGINE
This piston rings are made of special cast iron and the
shape of the top ring is barrel face, that of second ring is
taper under cut; and the oil ring has cutter expander.These
rings are very much effective for decreasing engine oil
consumption.
Connecting Rod
Rod Lock Washer
Oil Scraper
1
Fig. 7
-5-

4-5 CAMSHAFT
In the D type, 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. 8.)
In the B type, the camshaft is made of carbon steel, and EYlSB type has a pressured-fitted cam gear and a driven sproket.
(See Fig. 9.) The camshaft functions also as an output shaft, and is driven by 1/2 rotation of the crankshaft, Ball bearings
are used in the output shaft side.
J
Fig. 8
4-6 VALVE ARRANGEMENT
The exhaust vahe is located upstream of the coolingair with
the result thattheexhaust valve is intensiveiy 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. 10.)
Driven Sprocket
(Pressure-Fit)
Cam Gear
Fig. 9 (E Y 156)
I Exhaust Valve
Direction of Cooling Wind
Fig. 70
-6-
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