Subaru Robin EX35, EX40 Air-Cooled, 4-Cycle Gasoline Engine Service Repair Workshop Manual

1. SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2. PERFORMANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. FEATURES (EX35, 40 series) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. GENERAL DESCRIPTION OF ENGINE COMPONENTS . . . . . . . . . . . . . . . . 6 5. DISASSEMBLY AND REASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5-1 PREPARATIONS AND PRECAUTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5-2 SPECIAL TOOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5-3 DISASSEMBLY PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5-4 REASSEMBLY PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 6. ENGINE OIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7. MAGNETO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 8. IGNITION SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 9. WIRING DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 10. ELECTRIC STARTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 11. OIL SENSOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 12. AUTOMATIC DECOMPRESSION SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . 53 13. CARBURETOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 14. RECOIL STARTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 15. INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 16.TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 17. STANDARD REPAIR TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 17-1 STANDARD DIMENSIONS AND LIMITS OF USE . . . . . . . . . . . . . . . . . . 72 17-2 SERVICE DATA (The following are only for your reference.) . . . . . . . . . . . 77 17-3 TIGHTENING TORQUE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 17-4 AIR GAP AND CLEARANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 18.MAINTENANCE AND STORAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 CONTENTS Section Title Page

- 1 - 1. SPECIFICATIONS *Specifications are subject to change without notice. Model EX35D EX40D Type Air-Cooled, 4-Cycle, Slant Single-Cylinder, Horizontal P.T.O. Shaft, OHC Gasoline Engine Bore & Stroke mm (in.) 89 × 65 (3.50 × 2.56) Piston Displacement ml (cu.in.) 404 (24.65) Compression Ratio 8.3 Continuous Output kW(HP)/r.p.m. 5.5(7.5)/3000 6.3(8.5)/3600 6.3(8.5)/3000 7.0(9.5)/3600 Maximum Output kW(HP)/r.p.m. 7.4(10.0)/3600 8.8(12.0)/3600 Maximum Torque N ・ m / r.p.m. (kgf ・ m / r.p.m.) (ft ・ lb. / r.p.m.) 26/2400 (2.6/2400) (19.18/2400) 27/2400 (2.7/2400) (19.91/2400) Direction of Rotation Counterclockwise as viewed from the P.T.O. shaft side Valve Arrangement Overhead cam system Cooling System Forced air cooling system Lubrication System Splash lubrication system Lubricant Automobile engine oil ; Grade SE or higher (SG,SH or SJ in recomended) SAE 10W-30-----Under ordinary atmospheric temperatures SAE 5W-30-------In cold areas Capacity of Lubricant L 1.2 Carburetor Horizontal draft, Float type Fuel Automobile unleaded gasoline Fuel Consumption Rate g/kW ・ h (g/HP ・ h) 381 (280) Fuel Supply System Gravity type Fuel Tank Capacity L 7.0 Ignition System Transistorized magneto Spark Plug NGK BR-6HS Charging Capacity (Option) V-A 12-1A, 3A, 16.7A (Option) Starting System Recoil starter / Electric starter (Option) Governor System Centrifugal ﬂyweight system Dry Weight kg (lb.) 33 (72.75) Dimensions (L x W x H) mm (in.) 389 x 450 x 443 (15.31 x 17.72 x 17.44)

- 2 - 2. PERFORMANCE 2-1 MAXIMUM OUTPUT The Maximum output is the output of an engine with its throttle valve fully opened and considering that all the moving parts are properly broken in. A new engine may not produce full maximum output while its moving parts are still not broken-in. NOTE : Power curves shown in the following charts are made in conformity with SAE internal combustion engine standard test code J1349. 2-2 CONTINUOUS RATED OUTPUT The continuous rated output is the output of an engine at optimum governed speed which is most favorable from the view point of engin’s life and fuel consumption. When the engine is installed on a certain equipment, it is recommended that the continuous output required from the equipment to be kept below this continuous rated output. 2-3 MAXIMUM TORQUE The maximum torque is the torque at the output shaft when the engine is producing maximum output at a specific r.p.m..

- 3 - EX35D MAXIMUM TORQUE MAXIMUM HORSEPOWER r.p.m. REVOLUTION TORQUE OUTPUT CONTINUOUS RATED HP RECOMMENDED HORSEPOWER RANGE 2-4 PERFORMANCE CURVES

- 4 - EX40D MAXIMUM TORQUE MAXIMUM HORSEPOWER r.p.m. REVOLUTION TORQUE OUTPUT CONTINUOUS RATED HP RECOMMENDED HORSEPOWER RANGE

- 5 - 3. FEATURES (EX35, 40 series) 3-1 HIGH OUTPUT Thanks to the adoption of a cam profile exclusively for intake and exhaust and the optimization of the shape of the intake/exhaust port and the shape of the combustion chamber, the top-of-the-class-level maximum output is achieved. 3-2 EXTREMELY SILENT - SOFT TONE QUALITY EX engines are 2dBA quieter and softer in tone than other engines in the same class. This quiet and soft tone is achieved by: - Resin blower housing reduce noise leakage of mechanical noise. - Employment of an optimized capacity Rigid Muffler. 3-3 EXTREMELY EASY START Reliable Starting and Less Pulling Force are achieved by: Sophisticated Mechanical Compression Release System as well as newly designed Combustion Chamber. 3-4 EXTREMELY EASY MAINTENANCE Extreme ease of maintenance is realized by: - High Parts Commonality simplifies maintenance & lowers repair cost due to fewer parts for service. - Only with ordinary tools, routine maintenance, assembly and disassembly can be performed. 3-5 EXTREMELY ADVANCED TECHNOLOGY Extreme reliability and durability are achieved by: - Heavy Duty Chain Driven OHC System Oval type case-hardened steel links enhance performance and resist stretching, which result in extended maintenance free operation. - Completely New Main Bearing Cover’s Design Flush-mounted main bearing cover with lower moment of deformation significantly increases reliability and engine life. - Superior Cooling and Lubrication System Heat reduction is achieved by more efficient, larger and more numerous cooling fins on crankcase, cylinder and mounting base, as well as by outstanding oil delivery system. - Large Ball Bearings on both ends of crankshaft for maximum stability under demanding loads. - Cast Iron Cylinder Liner resists wear 3-6 EXTREME POWER AND PERFORMANCE Extremely Higher Power and Lower Fuel Consumption are realized by: - High speed and homogeneous combustion achieved by sophisticated Pentroof Combustion Chamber which includes Intake and Exhaust Valves located at optimum angle. - Straight Intake Port with minimal air flow resistance. Environmentally friendly EX engines comply with EPA Phase 2 and CARB Tier III Emission Regulations in the USA. Extreme application compatibility With four versatile models, existing slant-cylinder engines can be easily replaced.

- 6 - 4. GENERAL DESCRIPTION OF ENGINE COMPONENTS 4-1 CYLINDER AND CRANKCASE The cylinder and crankcase are aluminum die-casting as a single piece. A special cast iron cylinder liner is molded into the aluminum die-casting. The crankcase has a mounting surface on the output shaft side to which the main bearing cover is attached. The cylinder is inclined to the right at an angle of 25 degrees from the horizontal as viewed from the output shaft side. 4-2 MAIN BEARING COVER The main bearing cover is an aluminum die-casting, which is mounted on the output shaft side of the crankcase. By removing the main bearing cover, the inside of the engine can be inspected with ease. Pilots and bosses are machined into the cover to facilitate the direct coupling of the engine with machines such as generators and pumps. Oil gauges (fillers) are on both sides of the cover for easy maintenance. 4-3 CRANKSHAFT The crankshaft is forged carbon steel, and the crank pin is high-frequency inductionhardened. The crank sprocket used to drive the chain and the gear used to drive the governor gear are pressed into the output end of the shaft. 4-4 CONNECTING ROD AND PISTON The connecting rod is a specially heat-treated aluminum alloy die-casting. Its large and small ends function as bearings. A splasher built into the connecting rod lubricates by splashing engine oil. The piston is an aluminum alloy casting with grooves for mounting one compression ring and one oil ring. Fig.4-1 Fig.4-2 Fig.4-3 25° Fig.4-4

- 7 - Fig.4-6 Fig.4-5 4-7 VALVE ARRANGEMENT This engine has a chain-driven overhead cam and overhead valve construction, with a single cam which has individual profile for intake and exhaust to perform high output. Fig.4-7 EXHAUST VALVE INTAKE VALVE Fig.4-8 4-8 CYLINDER HEAD The cylinder head is on aluminum die-casting with a dome-shaped combustion chamber. The intake and exhaust ports are arranged in a cross direction to improve combustion efficiency. TOP RING OIL RING 1 2 TAPER THREE-PIECE CONSTRUCTION 1 2 4-6 CAMSHAFT The camshaft and the sprocket are made of special sintered alloy. They are constructed as a single piece. The camshaft is provided with intake and exhaust cam, and the decompression release lever is mounted on the sprocket shaft end side. 4-5 PISTON RINGS The piston rings are made of special cast iron. The profile of the top ring is a tapered face. The oil ring is designed for better sealing and less oil consumption, in combination with 3 pieces.

- 8 - 4-12 TIMING CHAIN Timing chain system is adopted and designed for lubricating for the upper portion of cylinder head. The timing chain is engaged between the sprocket portion of integrated camshaft in the cylinder head and the crankshaft gear sprocket. The sprocket teeth in particular shape are adopted to enhance the durability and to realize low noise level. 4-13 IGNITION SYSTEM The ignition system is a transistor controlled magneto system with the ignition timing set at 24 degrees before the top dead center. The magneto consists of a flywheel and ignition coil. The flywheel (cooling fan is separete from the flywheel) is directly mounted on the crankshaft and the ignition coil is directly mounted on the crankcase. * Model EX35 and 40 has a smooth advanced ignition timing system to improve starting performance. (For further details, refer to page 46, section “7. MAGNETO”.) Fig.4-10 Fig.4-11 4-11 LUBRICATION SYSTEM The rotating parts, sliding parts and valves of the engine are lubricated with oil in the crankcase. The oil is splashed onto the parts by the oil splasher on the connecting rod. 4-10 COOLING SYSTEM The engine uses a forced air-cooling system in which a synthetic resin cooling fan (which is separate from the flywheel), reduce noise and forces cooling air into the cylinder and cylinder head. Baffles are provided to guide the flow of cooling air. (As for with starting motor, baffle 1 is not mounted.) 4-9 GOVERNOR SYSTEM This engine is equipped with a centrifugal flyweight type governor that makes it possible to operate the engine at a constant speed, even with load variations. (The governor flyweights are mounted on a governor gear.) Fig.4-9 GOVERNOR GEAR TIMING CHAIN OIL SPLASHER IGNITION COIL FAN FLYWHEEL

Subaru Robin EX35, EX40 Air-Cooled, 4-Cycle Gasoline Engine Service Repair Workshop Manual

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