SERVICE MANUAL
CONTENTS Section Title Page 1. SPECIFICATIONS............................................... 1 2. PERFORMANCE............................................... 2 3. FEATURES.................................................... 4 4. GENERAL DESCRIPTION OF ENGINE COMPONENTS................ 5 5. DISASSEMBLY AND REASSEMBLY............................... 12 5-1 PREPARATIONS AND PRECAUTIONS........................... 12 5-2 SPECIAL TOOLS............................................. 12 5-3 DISASSEMBLY PROCEDURE.................................. 13 5-4 REASSEMBLY PROCEDURE................................... 27 6. ENGINE OIL................................................... 43 7. LUBRICATION SYSTEM......................................... 44 8. MAGNETO.................................................... 47 9. WIRING DIAGRAM.............................................. 48 10. AUTOMATIC DECOMPRESSION SYSTEM.......................... 49 11. CARBURETOR................................................ 50 12. RECOIL STARTER............................................. 58 13. INSTALLATION................................................ 63 14.TROUBLESHOOTING........................................... 65 15. STANDARD REPAIR TABLES.................................... 68 15-1 STANDARD DIMENSIONS AND LIMITS OF USE.................. 68 15-2 SERVICE DATA (The following are only for your reference.)........... 73 15-3 TIGHTENING TORQUE....................................... 74 15-4 AIR GAP AND CLEARANCE................................... 74 16.MAINTENANCE AND STORAGE.................................. 75
1. SPECIFICATIONS Model ER12 Type Air-Cooled, 4-Cycle, Single-Cylinder, Horizontal P.T.O. Shaft, OHC Gasoline Engine Bore Stroke mm (in.) 60 43 (2.36 1.69) Piston Displacement ml (cu.in.) 121 (7.38) Compression Ratio 9.6 Maximum Output kw(hp)/r.p.m. 2.6(3.5)/3600 Maximum Torque Direction of Rotation N m / r.p.m. (kgf m / r.p.m.) (ft lb. / r.p.m.) 7.3/2400 (0.74/2400) (5.38/2400) Counterclockwise as viewed from the P.T.O. shaft side Valve Arrangement Cooling System Lubrication System Lubricant Overhead cam system Forced air cooling system Trochoid Pump, Forced and Splash lubrication system Automotive detergent oil - SAE; #20, #30 or 10W-30 API service class; SE or higher (SG, SH or SJ is recommended) Capacity of Lubricant L (U.S. gal.) 0.35 (0.092) Carburetor Fuel Fuel Supply System Spark Plug Starting System Governor Air Cleaner system Horizontal draft, Float type or Diaphragm type Automobile unleaded gasoline Gravity type NGK CR5HSB Recoil starter Centrifugal flyweight type Semi wet type Dry Weight kg (lb.) 9.9 (21.78) Dimensions (L x W x H) mm (in.) 264 x 288 x 334 (10.39 x 11.34 x 13.15) : Float type Caburetor 264 x 288 x 336 (10.39 x 11.34 x 13.23) : Diaphragm type Caburetor *Specifications are subject to change without notice. - 1 -
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.. - 2 -
2-4. PERFORMANCE CURVES N m [kgf m] 0.9 8.0 0.8 MAXIMUM TORQUE 7.0 6.0 0.7 0.6 TORQUE 4.0 [HP] kw 3.0 MAXIMUM HORSEPOWER 3.0 OUTPUT 2.0 2.0 RECOMMENDED HORSEPOWER RANGE 1.0 1.0 0 0 2000 3000 4000 REVOLUTION r.p.m. - 3 -
3. FEATURES 3-1. DEVELOPED EXCLUSIVELY FOR RAMMER The new ER12 has been developed exclusively for rammer, which especially requires the engine for high durability, high power output and superb mountability among many construction machineries. 3-2. LIGHTWEIGHT AND COMPACT DESIGN ER12 has realized lightweight and compact design, while achieving high power output of 2.6kW (engine displacement 120cc) that enables to widely fulfill the operating weight of 60 to 80kg-class rammers, the lightest-in-class* weight of 9.9kg, and the smallest-in-class* on the length and width. 3-3. DESIGNED TO OFFER SUPERIOR MOUNTABILITY ER12 has been designed to offer superior mountability, which is valued for rammer engine, by the optimal center of gravity for right-and-ieft balance. 3-4. USER'S SAFETY AS WELL AS USER FRIENDLINESS ER12 offers several new functions as standard equipment, which has been required to rammer engine for user's safety as well as user friendliness, such as oil sensor that monitors the oil level not only at starting-up but also during operation, and automatic shutoff device that stops engine when the rammer rolls over or has no operation with idling. 3-5. EASE OF MAINTENANCE AND ECONOMICAL EFFICIENCY ER12 has beeh designed in consideration of ease of maintenance and economical efficiency, such as adopting solid crank case or the newly developed resinous dust-proof air cleaner for realizing ease of maintenance, realizing longer operational hours without oil-refilling. * FHI researches - 4 -
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. And the lib is made for the crankcase room center cum oil shelter plate, that improvement breather function and strength up. And inside of the crankcase has large rib for oil shelter which to inprove the breather function and stiffness. 4-2 MAIN BEARING COVER The main bearing cover is an aluminum die-casting with heavy-duty structure to endure to install on rammers, 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 for direct mounting of the engine onto rammers. And it have suction pipe, oil pump, oil filter and oil pressure switch. 4-3 CRANKSHAFT The crankshaft is forged carbon steel, and the crank pin is high-frequency inductionhardened. The crank pulley used to drive the timing belt 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. The piston is an aluminum alloy casting with grooves for mounting one compression ring and one oil ring. JCC - 5 -
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. 1 1 TOP RING TAPER 2 2 OIL RING THREE-PIECE CONSTRUCTION 4-6 CAMPULLEY The campulley is made of special nylon. They are constructed as a single piece. The campulley is provided with intake and exhaust cam, and the decompression release lever is mounted on the sprocket shaft end side. 4-7 VALVE ARRANGEMENT This engine has a belt-driven overhead cam and overhead valve construction, with a single cam performing both intake and exhaust operations. EXHAUST VALVE INTAKE VALVE - 6 -
4-8 CYLINDER HEAD The cylinder head is on aluminum die-casting with a lens-shaped combustion chamber. The intake and exhaust ports are arranged in a cross direction to improve combustion efficiency. 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.) GOVERNOR GEAR 4-10 COOLING SYSTEM The engine uses a forced air-cooling system in which a cooling fan on the frywheel, reduce noise and forces cooling air into the cylinder and cylinder head. Baffle is provided to guide the flow of cooling air. 4-11 LUBRICATION SYSTEM Lubricant (engine oil) is sprayed onto the parts with pressure spray by the trochoid type of oil pump, and those parts splashes to the parts necessary to be lubricated. The trochoid pump is driven by the crankshaft. Lubricant is wholly filtered by the oil pump filter plugged in the under of the main bearing cover. - 7 -
4-12 TIMING BELT Timing belt system is adopted and designed for lubricating for the upper portion of cylinder head. The timing belt is engaged between the campulley in the cylinder head and the crankshaft gear. The pulley and the gear teeth in round shape are adopted to enhance the durability and to realize low noise level. CAMPULLEY TIMING BELT DRIVEPULLEY CRANKSHAFT 4-13 IGNITION SYSTEM The ignition system is a pointless flywheel magnet by a digital control. The magneto consists of a flywheel and ignition coil with CPU (Central Processing Unit.) and CDI (Capacitor Discharge Ignition.). The flywheel is directly mounted on the crankshaft and the ignition coil is directly mounted on the crankcase. IGNITION COIL FLYWHEEL THICKNESS GAUGE FAN 4-14 CARBURETOR The engine is equipped with two types of horizontal draft carburetors, one has a float controlled fuel system and a fixed main jet, and another is diaphragm type. The carburetors are calibrated carefully for sure starting, good acceleration, less fuel consumption and maximum output. For details, refer to page 50, section 11-3 FLOAT CARBURETOR As details of diaphragm type, refer to page 53, section 11-4 DIAPHRAGM CARBURETOR. FLOAT TYPE DIAPHRAGM TYPE - 8 -
4-15 AIR CLEANER The air-cleaner is a heavy-duty type with a dual element system; the primary one is an urethane foam (semi-wet) and secondary one is a semi wet type element. AIR CLEANER BASE ELEMENT URETHANE FOAM AIR CLEANER COVER 4-16 DECOMPRESSION SYSTEM The automatic decompression system is mounted on the campulley. It opens the exhaust valve before the compression top, thereby alleviating the compression pressure and reducing the force required to pull the recoil starter. During engine operation, the decompression system is overpowered by centrifugal force and compression is fully utilized to produce power. RETURN SPRING EXHAUST VALVE ROCKER ARM (EXHAUST VALVE SIDE) CAMSHAFT - 9 -
4-17 SECTIONAL VIEW OF THE ENGINE Cross sectional view across the shaft SPARK PLUG CYLINDER HEAD PISTON RECOIL STARTER IGNITION COIL PISTON RING PISTON PIN OIL PRESSURE SWITCH OIL PUMP P.T.O. SHAFT CRANKSHAFT ADAPTER FLYWHEEL MAIN BEARING COVER CRANKCASE SER No. (Stamping) PLUG SUCTION PIPE - 10 -
Cross sectional view along the shaft CAMPULLEY EXHAUST VALVE ROCKER COVER ROCKER ARM INTAKE VALVE FLOAT TYPE CARBURETOR CARBURETOR (DIAPHRAGM TYPE) MUFFLER AIR CLEANER PISTON RING TIMING BELT GOVERNOR LEVER STOP SWITCH CONNECTING ROD SPEED CONTROL LEVER OIL GAUGE GOVERNOR GEAR BREATHER COVER SER No. (Stamping) CRANKSHAFT OIL DRAIN PLUG CRANKCASE - 11 -
5. DISASSEMBLY AND REASSEMBLY 5-1 PREPARATIONS AND PRECAUTIONS 1) When disassembling the engine, memorize the location of each part so that you can reassemble the engine correctly. If necessary, attach identification tags with the required assembly information to the parts. 2) Store groups of parts in separate boxes. This will make reassembly easier. 3) To prevent parts from being mislaid, keep each group provisionally assembled after removing the parts from the engine. 4) Handle the disassembled parts with the utmost care. Clean them with cleaning oil if necessary. 5) Use the correct tools in the correct way when disassembling and reassembling the engine. 5-2 SPECIAL TOOLS Tool name Use Commercially available product Flywheel puller For pulling off the flywheel Commercially available product Commercially available product Piston ring plier Piston ring compresser For removing and installing piston rings For holding piston rings Commercially available product Chain wrench For locking the flywheel FLYWHEEL PULLER PISTON RING PLIER PISTON RING COMPRESSER CHAIN WRENCH - 12 -
5-3 DISASSEMBLY PROCEDURE Step Parts to remove Remarks and procedures Fasteners 1 Drain the engine oill Remove a drain plug (M8 x 12mm) located on both sides of the case. Take care not to lose the gaskets. * To discharge oil quickly, remove the oil gauge(m22). 12 mm spanner 2 Air cleaner Remove breather pipe from rocker cover. 10mm box spanner M6 nut:2pcs. STEP 2 GASKET(INTAKE) BREATHER PIPE CLEANER BASE CLEANER COVER M6 SELF LOCK NUT : 2pcs. ELEMENT URETHANE FOAM OIL GAUGE GASKET (Rubber ) GASKET (Aluminum ) M8 DRAIN PLUG : 1pc. STEP 1-13 -
Step Parts to remove Remarks and procedures Fasteners 3 Muffler and Muffler cover (1) Remove the muffler cover from the muffler and gasket(muffler). (2) Remove the muffler from the cylinder head. Take care not to lose the gasket. * Take care not to cut your hand with muffler gasket. 10mm box spanner or spanner 13mm box spanner M6 18mm:3pcs. M6 nut:2pcs. 4 Recoil starter Disconnect wire of stop switch first, then remove recoil starter. 10mm box spanner M6 20mm:2pcs. M6 14mm:1pc. RECOIL ASSY M6 x 14 FLANGE BOLT : 1 pc. GASKET (MUFFLER) MUFFLER M6 SELF LOCK NUT : 2pcs. STEP 3 M4 SCREW : 2 pcs. M6 x 18 FLANGE BOLT : 3 pcs. STOP SWITCH Do Not remove the plug. M6 x 20 FLANGE BOLT : 2 pcs. MUFFLER COVER STEP 4-14 -
Step Parts to remove Remarks and procedures Fasteners Carburetor, Insulator Remove the linkage bushing from governor rod. (1) Loosen the and remove the governor lever from the governor shaft. There is no need to remove the bolt. 10mm box spanner or spanner M6 20mm:1pc. M6 Nut:1pc. 5 (2) Remove the governor spring. (3) Remove the governor rod and the rod spring from the carburetor. Remove the carburetor from the cylinder head. Remove the insulator. GASKET (INSULATOR) BLACK INSULATOR GASKET (CARBURETOR) BROWN ROD SPRING LINKAGE BUSHING CARBURETOR (FLOAT TYPE) CYLINDER HEAD GOVERNOR ROD STEP 5 GOVERNOR LEVER CYLINDER HEAD GASKET (INSULATOR) BLACK STEP 5 A INSULATOR 2 GASKET (CARBURETOR) BLACK BOLT GOVERNOR SPRING NUT DETAIL A CARBURETOR (DIAPHRAGM TYPE) GASKET (CARBURETOR) BROWN SELF LOCK NUT INSULATOR 1 GASKET (INSULATOR) BLACK A INTAKE PIPE - 15 -
Step Parts to remove Remarks and procedures Fasteners 6 Speed control lever and Base plate Remove the speed control lever and base plate from the crankcase. (If necessary) 10mm box spanner M6 10mm:2pcs. 14mm box spanner Pivot bolt:1pc. NUT STEP 6 SET SCREW (HIGH SPEED) BASE PLATE SET SCREW (LOW SPEED) SPEED CONTROL LEVER SWIVEL (NUT) M4 x 0.7 FRICTION WASHER (NYLON) SPACER RETURN SPRING PIVOT BOLT M6 10 FLANGE BOLT:2pcs. PIVOT BOLT Tightening torque : 7.0-9.0 N m (70-90 kgf cm) (5.1-6.5 ft lb.) SPEED CONTROL AY GOVERNOR SPRING STEP 6 M6 20 BOLT GOVERNOR LEVER M6 NUT - 16 -
Step Parts to remove Remarks and procedures Fasteners 7 8 Cylinder baffle Remove the Cylinder baffle. (If necessary) 10 mm box spanner M6 x 10 mm : 3 pcs. Breather Remove the breather cover and plate. (If necessary) 8 mm box spanner M6 x 20 mm : 4 pcs. 9 Ignition coil Remove the spark plug cap from the spark plug. Disconnect wire of oil pressure switch. Remove the ignition coil from the crankcase. 10 mm box spanner M6 x 25 mm:2 pcs. CYLINDER BAFFLE STEP 7 M6 10 FLANGE BOLT:3pcs. M6 20 FLANGE BOLT:4pcs. Disconnect the wire from the portion BREATHER PLATE GASKET (BREATHER PLATE) STEP 8 BREATHER COVER GASKET (BREATHER COVER) SPARK PLUG SPARKPLUG RUBBER CAP IGNITION COIL STEP 9 M6 20 BOLT : 2pcs. SWITCH (OIL PRESSURE) - 17 -
Step Parts to remove Remarks and procedures Fasteners Flywheel Remove the starting pully from the flywheel. Fit a box wrench or a socket wrench on the flywheel nut and loosen the nut by knocking the wrench sharply with a hammer. (See Fig.4-a) 19 mm socket wrench M14 nut : 1pc. 10 NOTE: 1. Do not insert screwdriver or other object between the flywheel blades which is a synthetic resin, otherwise the risk of damaging the blades might be occurred. 2. Knock the wrench with a hammer in a counter clockwise direction. Remove the flywheel from the crankshaft. Leave the nut temporarily to prevent the flywheel from dropping out. Fit the flywheel puller as shown in Figure4-b and remove the flywheel from the crankshaft by rotating the bolt at the center in a clockwise direction.(knock the center bolt with a hammer sometimes) Flywheel puller HAMMER ALUMINUM BAR Fig.4-a STEP 10 Fig.4-b NUT PULLER - SCREWDRIVER WOODRUFF KEY M14 FLANGE NUT : 1pc. FLYWHEEL - 18 -
Step Parts to remove Remarks and procedures Fasteners 11 Spark plug Remove the spark plug from the cylinder head. 16mm plug wrench 12 Rocker cover (1) Remove the rocker cover from the cylinder head. (2) Remove the gasket (rocker cover) 10mm box spanner M6 14mm : 2pcs. 13 Rocker arm Remove the pin (rocker arm)and the rocker arm from the cylinder head at the compression top dead center. (See Fig.4-c) Pliers STEP 11 SPARK PLUG M6 20 FLANGE BOLT : 2pcs. ROCKER COVER VIEW A STEP 12 GASKET (ROCKER COVER) ADJUSTMENT SCREW, NUT ROCKER ARM (EXHAUST SIDE) Remove the pin the allow direction Matching mark ROCKER ARM (INTAKE SIDE) PIN(ROCKER) STEP 13 A Cylinder head surface Fig.4-c - 19 -
Step Parts to remove Remarks and procedures Fasteners 14 Oil pump Remove oil pump cover o-ring outer rotor and inner rotor. 8mm box wrench M6 12mm:4pcs. STEP 14 OUTER ROTOR MAIN BEARING COVER OIL PUMP COVER M6 12 FLANGE BOLT:4pcs. INNER ROTOR O-RING (SYNTHETIC RUBBER) - 20 -
Step Parts to remove Remarks and procedures Fasteners 15 Main bearing cover Remove the flange bolts of main bearing cover from the crankcase. Remove the main bearing cover while tapping gently around the cover using a plastic hammer or similar tool. (See Fig.4-d) Be careful not to damage the oil gauge or oil seal or not to lose the pipe knocks. 12mm box wrench M8 55mm:6pcs. SPACER STEP 15 M8 55 FLANGE BOLT : 6pcs. MAIN BEARING COVER CRANKCASE MAIN BEARING COVER PLASTIC HAMMER - 21 - Fig.4-d
Step Parts to remove Remarks and procedures Fasteners 16 Switch (Oil pressure) Remove the oil pressure switch. (If necessary) 24mm spanner 17 Plug and suction pipe Remove the plug and suction pipe from the main bearing cover. (If necessary) M5 12mm:2pcs. STEP 16 SWITCH (OIL PRESSURE) MAIN BEARING COVER A STEP 17 PLUG AY (OIL FILTER) SUCTION PIPE MESH SCREEN M14 O-RING (SYNTHETIC RUBBER) PLUG AY M5 12 SCREW : 2pcs. VIEW A - 22 -
Step Parts to remove Remarks and procedures Fasteners 18 Campulley (1) Remove the retaining bolt of pin (campulley) from the cylinder head. (2) Remove the pin (campulley), taking care not to scratch the O-ring. (3) Remove the timing belt from the campulley and then take out the campulley. (4) Remove the timing belt from the crankshaft. 10mm box spanner M6 8mm:1pc. Pliers O-RING (SYNTHETIC RUBBER) PIN (CAMPULLEY) CYLINDER HEAD M6 8 FLANGE BOLT : 1pc. TIMING BELT CRANKCASE STEP 18 CAMPULLEY TIMING BELT DRIVEPULLEY CRANKSHAFT - 23 -
Step Parts to remove Remarks and procedures Fasteners 19 Cylinder head (1) Remove the cylinder head from the crankcase. (2) Remove the cylinder head gasket from the cylinder head. Take care not to lose the pipe knock 12mm box spanner M8 98mm:4pcs. 20 Intake and exhaust valves (1) Remove the collet valve from the spring retainer. (If necessary) (2) Remove the intake valve and the exhaust valve. STEP 19 STEP 20 M8 98 FLANGE BOLT:4pcs. COLLET VALVE SPRING RETAINER STEM SEAL (INTAKE ONLY) VALVE SPRING GASKET (HEAD) CYLINDER HEAD KNOCK PIN EXHAUST VALVE CRANKCASE INTAKE VALVE - 24 -
Step Parts to remove Remarks and procedures Fasteners 21 Connecting rod and piston (1) Scrape off any carbon from the cylinder and the piston head, then remove the connecting rod bolt. (2) Remove the connecting rod cap. (3) Rotate the crankshaft until the piston comes to its top position. Push the connecting rod and remove the piston from the upper part of the cylinder. 8mm box spanner M5 25mm:2pcs. 22 Piston and piston rings (1) Remove the piston clips(2pcs.). Take out the piston pin and then remove the piston from the connecting rod small end, taking care not to damage the connecting rod small end. (2) Remove the piston rings from the piston by spreading them at the gap. Take special care not to damage the rings when doing this. CLIP PISTON RING STEP 22 PISTON PISTON PIN CONNECTING ROD STEP 21 CLIP UPPER PART OF THE CYLINDER CRANKSHAFT CONNECTING ROD CAP CONNECTING ROD BOLT : 2pcs. - 25 -
Step Parts to remove Remarks and procedures Fasteners 23 Crankshaft (1) Remove the woodruff key (for the flywheel magneto). (2) Remove the crankshaft from the crankcase by tapping its magneto side end with a plastic hammer, taking care not to damage the oil seal. Plastic hammer OIL SEAL (PRESS FITTING) WASHER STEP 23 E-CLIP CRANKSHAFT GOVERNOR SHAFT WASHER - 26 -
5-4 REASSEMBLY PROCEDURE 5-4-1 NOTES ON REASSEMBLY (1) Clean the each parts carefully, taking special care with the piston, cylinder, crankshaft, connecting rod and bearings. (2) Scrape off any carbon deposits on the cylinder head and the piston head. Be particularly careful when removing carbon from the piston ring grooves. (3) Inspect the oil seals for any damage to the lip. Replace them if damaged. Apply oil to the lip before reassembly. (4) Replace all the gaskets with new ones. (5) Replace the keys, pins, bolts and nuts with new ones, if necessary. (6) Tighten nuts and bolts to the specified torque settings. (7) When reassembling the engine, apply oil to all moving parts. (8) Check clearances and end plays and adjust, if necessary. (9) When mounting any major part during reassembly of the engine, rotate it with your hand to check for any jamming or abnormal noise. 5-4-2 ASSEMBLY STEPS AND PRECAUTIONS (1) CRANKSHAFT (a) Wrap the key-way portion of the crankshaft with polyvinyl tape and insert the crankshaft into the crankcase, taking care not to damage the oil seal lip. CRANKSHAFT (b) Insert the woodruff key (for the flywheel magneto). NOTE: Do not insert the woodruff key before inserting the crankshaft into the crankcase. POLYVINYL TAPE - 27 -
(2) PISTON AND PISTON RINGS (a) Install each piston ring in the correct groove of the piston by widening it enough to slide it over the piston. NOTE: Be careful not to twist the rings too much, as they may be damaged. Install the oil ring first, followed by the top ring. When installing the piston ring, make sure that the "R" mark is face up. OPEN ENDS OF PISTON RING 1 1 TOP RING TAPER 2 2 OIL RING THREE-PIECE CONSTRUCTION MARK R - 28 -
(3) PISTON AND CONNECTING ROD The piston is attached to the connecting rod by the piston pin. When assembling the piston and connecting rod, make sure to align the mark on the piston head with the JCC mark on the connecting rod. NOTE 1: Before assembling the connecting rod, apply oil to its small end. NOTE 2: Be sure to insert the clips in the two ends of the piston pin and check the clips for any play. JCC When assembling the piston and connecting rod, make sure to align the mark on the piston head with the JCC mark on the connecting rod. (4) CONNECTING ROD (a) Install the piston and connecting rod assembly into the cylinder by holding the piston rings with the ring guide, with the JCC mark on the connecting rod on the flywheel side. (If you do not have a ring guide, hold the piston rings with the fingers and tap the upper part of the piston with a piece of wood.) JCC PISTON RING GUIDE AND PISTON RING JCC MARK NOTE 1: Apply oil to the piston rings, the large end of the connecting rod and cylinder before installing the connecting rod into the cylinder. NOTE 2: The piston ring gaps should be positioned around the piston at 180-degree intervals. P.T.O SHAFT SIDE FLYWHEEL SIDE OIL RING 180 TOP RING FLYWHEEL SIDE ("JCC" MARK SIDE) - 29 -
(b) Rotate the crankshaft down to the bottom dead center and lightly tap the piston head until the large end of the connecting rod touches the crank pin. (c) To mount the connecting rod, line up the matching marks and fit the clinch portions firmly together. ALIGNMENT MARKS M5 25mm Connecting rod bolt : 2pcs. (8mm box wrench) Tightening torque 6.0-8.0 N m (60-80 kgf cm) (4.3-5.8 ft lb.) (d) Check for free movement of the connecting rod by turning the crankshaft slowly. Make sure press fitting to contact exactly between stem seal and Cylinder head. (5) INTAKE AND EXHAUST VALVES Take the following points into account when mounting the intake and exhaust valves on the cylinder head. NOTE 1: Replace the valve with a new one if it shows signs of wear. NOTE 2: Carefully scrape off any carbon deposits on the combustion chamber. Apply oil to the valve stems before mounting the intake and exhaust valves. Insert the valves in the cylinder head and place it on a level workbench. Next, mount the valve springs, the spring retainers and collet valves. (Mount the stem seal on the intake valve guide.) COLLET VALVE SPRING RETAINER VALVE SPRING CYLINDER HEAD Apply oil STEM SEAL CYLINDER HEAD VALVE GUIDE STEM SEAL (INTAKE ONLY) Apply oil EXHAUST VALVE INTAKE VALVE - 30 -
(6) CYLINDER HEAD (a) Inspect and repair any scratches on mounting surface and replace head gasket to new one before installing. (b) Insert the pipe knocks between crankcase and cylinder head. Install cylinder head onto cylinder with new head gasket. Apply oil to the screw thread. Tighten four flange bolts evenly in three steps by the following tightening torque: Cylinder head M8 98mm bolt : 4pcs. Tightening torque 1 st step 2 st step Final step 5.0 N m (50 kgf cm) (3.6 ft lb.) 9.8 N m (100 kgf cm) (7.2 ft lb.) 20.0-24.0 N m (200-240 kgf cm) (14.4-17.7 ft lb.) (7) SETTING THE TIMING BELT (a) Set the crankshaft to the top dead center. (b) Set the timingbelt to the drive pulley on the crankshaft. CAMPULLEY (c) Install the campulley to the cylinder head. Meet the matching mark of campulley and cylinder head. (d) Mounting the campulley on the cylinder head. Mount the campulley on the cylinder head by inserting the pin (campulley)through the head. Fix the bolt to prevent the pin (campulley) from coming out. M6 8mm flange bolt : 1pc. Tightening torque 4.0-6.0 N m (40-60 kgf cm) (2.9-4.3 ft lb.) DRIVE PULLEY TIMING BELT CRANKSHAFT Matching mark CYLINDER HEAD PIN(CAMSHAFT) Cylinder head surface - 31 - O-RING M6 x 8 FLANGE BOLT : 1pc.
(8) ADJUST CRANKSHAFT END PLAY (1) Adjust end play to 0.2 mm (0.008") using the proper spacer. The proper spacer may be determined in the following manner. DEPTH GAUGE 1) Measure the height A (From the mating surface to the inner race of the ball bearing.) 2) Measure the depth B (From the mating surface to the drive pulley.) B A = SIDE CLEARANCE (mm) (SIDE CLEARANCE) 0.2 mm = THICKNESS OF CRANKSHAFT SHIM (mm) B A = SIDE CLEARANCE (in.) (SIDE CLEARANCE) 0.008 in. = THICKNESS OF CRANKSHAFT SHIM (in.) Following are available spacer shims. CRANKSHAFT DRIVE PULLEY DRIVE PULLEY CRANKCASE MAIN BEARING COVER BALL BERARING CRANKSHAFT SPACER SHIMS T = 0.8 mm (0.031 in.) T = 1.0 mm (0.039 in.) T = 1.2 mm (0.047 in.) CRANKCASE This image slightly differs from the actual engines. - 32 -
(9) MAIN BEARING COVER (a) Insert the plug, suction pipe and oil pressure switch. PLUG SUCTION PIPE OIL PRESSURE SWITCH 0.8-1.2 N m (8-12 kgf cm) (0.6-0.9 ft lb.) 6.0-8.0 N m (60-80kgf cm) (4.3-5.8 ft lb.) 8.0-10.0 N m (80-100 kgf cm) (5.8-7.2 ft lb.) (b) Apply oil to the bearing and the oil seal lip when mounting the main bearing cover. Also apply sealant (Three Bond 1280B ) to the surface of the crankcase. To avoid damaging the oil seal lip, wrap the crankshaft key-way portion with polyvinyl tape before mounting the main bearing cover. NOTE: Turn the lever portion of governor shaft does to the engine base. Also apply sealant (Three Bond 1280B ) to the surface. GOVERNOR SHAFT MAIN BEARING COVER SPACER ENGINE BASE M8 55 FLANGE BOLT:6pcs. Tightening torque 24.0-26.0 N m (240-260 kgf cm) (17.7-18.8 ft lb.) GOVERNOR GEAR Turn the lever portion of governor shaft does to the engine base. - 33 -
(10) OIL PUMP and COVER (1) Apply oil to inner and outer rotors of oil pump and attach them in position. (2) Set O-ring in position. (3) Install oil pump cover with the allow marking upwards. OIL PUMP COVER OUTER ROTOR ALLOW MARKING O-RING (SYNTHETIC RUBBER) M6 12mm flange bolt : 4pcs. Tightening torque 7.0-9.0 N m (70-90 kgf cm) (5.1-6.5 ft lb.) INNER ROTOR M6 12 FLANGE BOLT : 4pcs. MAIN BEARING COVER (11) ROCKER ARM (a) Conduct this job at the compression top dead center. The position of two matching marks on campulley is in parallel with the cylinder head surface at a time. NOTE: Make sure that the piston is at the compression top dead center by checking mutual position between the flywheel and the ignition coil is at the top. (b) Pass the pin (rocker arm) through the rocker arm and mount them on the cylinder head. Matching mark CAMPULLEY PIN(ROCKER) SLIT Cylinder head surface - 34 -
(12) VALVE CLEARANCE ADJUSTMENT Temporarily fit the flywheel. Rotate the crankshaft up to the compression top dead center and insert the thickness gauge between the valve and the adjusting screw of rocker arm to measure the clearance. Adjust the valve clearance insert the thickness gauge to the portions. [Adjustment method] Loosen the nut on the adjustment screw and turn the screw to adjust the valve clearance. When the valve clearance is correct, tighten the nut. Valve clearance (when the engine is cold) Intake valve side Exhaust valve side 0.11-0.16 mm (0.0043-0.0063 in.) Tightening torque 5.0-7.0 N m (50-70 kgf cm) (3.6-5.1 ft lb.) NOTE: After adjusting the valve clearances, rotate the crankshaft and check again that the intake and exhaust valve clearance are correct. APPLY OIL (13) ROCKER COVER Replace the gasket with a new one, and mount the rocker cover. M6 20 mm flange bolt : 2 pcs. Tightening torque 5.0-7.0 N m (50-70 kgf cm) (3.6-5.1 ft lb.) ROCKER COVER GASKET (ROCKER COVER) SPARK PLUG - 35 -
(14) SPARK PLUG Remove any carbon deposits from the spark plug and inspect the electrode for damage before mounting. Replace with a new one, if necessary. Spark plug : NGK CR5HSB (16 mm plug wrench) Electrode gap 0.6-0.7 mm (0.024-0.028 in.) Tightening torque New spark plug 10.0-12.0 N m (100-120 kgf cm) (7.2-8.7 ft lb.) Re-tightening torque 23.0-27.0 N m (230-270 kgf cm) (16.6-19.5 ft lb.) (15) FLYWHEEL (1) Put the woodruff key in the keyway of crankshaft. Wipe off oil and grease thoroughly from the tapered portion of crankshaft and flywheel center hole. (2) Install the flywheel to crankshaft. Tighten the flywheel nut. Tightening torque 60.0-70.0 N m (600-700 kgf cm) (43.4-50.6 ft lb.) M14 nut : 1 pc. (19mm box wrench) FLYWHEEL CHAIN WRENCH IGNITION COIL FLYWHEEL THICKNESS GAUGE (16) IGNITION COIL When mounting the ignition coil, insert a thickness gauge between the ignition coil and the flywheel to check the air gap. FAN Air gap 0.3-0.5 mm (0.012-0.020 in.) SWITCH (OIL PRESSURE) SPARK PLUG RUBBER CAP Tightening torque 7.0-9.0 N m (70-90 kgf cm) (5.1-6.5 ft lb.) M6 20 mm bolt and washer : 2 pcs. Connect wires referring to the wiring diagram. IGNITION COIL - 36 -
(17) BREATHER Assemble gasket (breather plate), breather plate, gasket(breather cover) refer to the following. M6 20 mm flange bolt : 4 pcs. Tightening torque 7.0-9.0 N m (70-90 kgf cm) (5.1-6.5 ft lb.) BREATHER PLATE BREATHER COVER M6 20 FLANGE BOLT:4pcs. P.T.O.SHAFT SIDE FLYWHEEL SIDE P.T.O.SHAFT SIDE FLYWHEEL SIDE GASKET (BREATHER PLATE) GASKET (BREATHER COVER) (18) BAFFLE Mount the cylinder baffle to the crankcase with the bolts. M6 10 mm bolt : 3 pcs. - 37 -
(19) SPEED CONTROL Install the speed control to the top breather cover with the bolts. BREATHER COVER FLANGE BOLT M6 10 mm flange bolt : 2 pcs. SPEED CONTROL AY NUT SET SCREW (HIGH SPEED) BASE PLATE SET SCREW (LOW SPEED) SPEED CONTROL LEVER SWIVEL (NUT) M4 x 0.7 FRICTION WASHER (NYLON) SPACER RETURN SPRING PIVOT BOLT M6 10 FLANGE BOLT:2pcs. - 38 -
(20) GOVERNOR LEVER, CARBURATOR (a) Mount the governor lever on the governor shaft. Do not adjust the bolt on the governor lever yet. (b) Attach the governor rod and rod spring to ROD SPRING LINKAGE BUSHING GOVERNOR ROD the governor lever. (c) Replace the gasket of insulator with a new one and mount the insulator on the cylinder head intake side. GOVERNOR LEVER GOVERNOR SPRING (d) Hook governor rod to the governor lever and throttle lever of carburator. mount the carburator to the cylinder head. (e) Hook the linkage bushing to the governor rod. BOLT AND WASHER AY NUT (21) AIR CLEANER BASE Insert the breather pipe into the breather cover and air cleaner base then mount the air cleaner base. M6 salf lock nut:2pcs. Tightening torque Float type carburetor 7.0-9.0 N m (70-90 kgf cm) (5.1-6.5 ft lb.) Diaphragm type carburetor 4.0-5.0 N m (40-50 kgf cm) (2.9-3.6 ft lb.) Then install the element and cleaner cover. GASKET (INSULATOR) RUBBER PIPE GASKET (CARBURETOR) AIR CLEANER BASE INSULATOR 2 M5 SELF LOCK NUT : 2pcs. GASKET (CARBURETOR) ELEMENT FLOAT TYPE CARBURETOR AIR CLEANER COVER - 39 -
GASKET (INSULATOR) M5 x 70mm BOLT : 2 pcs. INSULATOR 2 INSULATOR 1 GASKET (INSULATOR) GASKET (CARBURETOR) ADAPTER (INTAKE) RUBBER PIPE GASKET (CARBURETOR) AIR CLEANER BASE M5 SELF LOCK NUT : 2pcs. RUBBER PIPE ELEMENT DIAPHRAGM TYPE CARBURETOR AIR CLEANER COVER (22) ADJUST GOVERNOR SYSTEM (1) Turn the speed control lever all the way toward the high speed position. (2) Check that the governor lever is pulled by the governor spring and carburetor throttle valve is fully open. 550 565 551 (3) Turn the governor shaft clockwise all the way using a screw driver, and tighten lock bolt to secure the lever on the shaft. 562 567 560 540 GOVERNOR ROD SPRING GOVERNOR LEVER Normal hooking position GOVERNOR SHAFT GOVERNOR ROD GOVERNOR SPRING SPEED CONTROL LEVER DIAPHRAGM CARBURETOR - 40 -
(23) RECOIL STARTER Attach recoil starter to crankcase. Tighten flange bolts. M6 x 20 mm flange bolt : 2 pc. M6 x 14 mm flange bolt : 1 pcs. Tightening torque 7.0-9.0 N m (70-90 kgf cm) (5.1-6.5 ft lb.) Insert the high tension cord from the ignition coil into the notch of the blower housing so as not to pinch the cord. (24) STOP SWITCH (1) Install stop switch to blower housing. (2) Connect wires referring to the wiring diagram. (25) MUFFLER (1) Mount the muffler and the gasket on the cylinder head. Self lock nut : 2 pcs. Tightening torque M6 x 18 BOLT : 3 pcs. MUFFLER COVER SELF LOCK NUT : 2 pcs. 19.0-21.0 N m (190-210 kgf cm) (13.7-15.2 ft lb.) (2) Mount the muffler cover on the muffler. M6 18 mm bolt : 3 pcs. Tightening torque 7.0-9.0 N m (70-90 kgf cm) (5.1-6.5 ft lb.) MUFFLER GASKET (MUFFLER) - End of the reassembly - - 41 -
(26) EXTERNAL INSPECTION Reassembly is completed. Check that the wiring is correct and that there are no loose nuts and bolts or any other faults visible on the outside of the engine. (27) FILLING WITH ENGINE OIL Use the automobile engine oil of API service class SE or higher grade. The amount of oil, refer to the table below. Engine oil volume (maximum) 0.35L (28) BREAK-IN OPERATION A new engine or an engine that has been completely overhauled by being fitted with a new piston, rings, valves and connecting rod should be thoroughly RUN-IN before being put back into service. Good bearing surfaces and running clearances between the various parts can only be established by operating the engine under reduced speed and loads for a short period of time. While the engine is being tested, check for oil leaks. Make final carburetor adjustment and regulate the engine operating speed. Step Load Engine Speed Time Step 1 No Load 2500 r.p.m. 10 min. Step 2 No Load 3000 r.p.m. 10 min. Step 3 No Load 3600 r.p.m. 10 min. Step 4 1.3 kw 3600 r.p.m. 30 min. Step 5 2.6 kw 3600 r.p.m. 30 min. - 42 -
6. ENGINE OIL Using engine oil of the correct grade and viscosity greatly lengthens engine life and improves performance. Too much or too little oil can also result in serious problems, including engine seizure. 6-1 CLASSIFICATION BY OIL GRADE API (American Petroleum Institute) Classification SA SB SC SD SE SF SG SH SJ Grades suited for Robin Engine: SE or higher (SG,SH or SJ in recomended) 6-2 CLASSIFICATION BY OIL VISCOSITY SAE (Society of Automotive Engineers) Single grade 5W 10W 20W #20 #30 #40 Multigrade 10W-30 10W-40 Ambient temperature Be sure to use automobile engine oil of the viscosity shown in the table above, depending on environmental air temperature. When the air temperature falls below 20 or rises above 40, be sure to choose engine oil of appropriate viscosity and grade, according to the prevailing conditions. * Care must be taken when using multi-grade engine oil, because the oil consumption rate tends to increase when the air temperature is high. 6-3 ADDING AND CHANGING ENGINE OIL Engine oil inspection and filling up.. Every time you use the engine (add engine oil up to the designated maximum level) Engine oil change.............. First time.......... After 20 hours use Thereafter......... Every 100 hours use - 43 -
7. LUBRICATION SYSTEM 7-1 OPERATION AND FUNCTION Forced pressure spray and splash lubrication system are adopted, in combination with trochoid oil pump and plugged filter. The trochoid type oil pump is driven by crankshaft, and sprays pressurized engine oil to the crankshaft, connecting rod and inside of crankcase. The engine oil in the oil pan is fed through the suction pipe, oil pump filter and gallery of main bearing cover. The engine oil is provided onto the rotating portions such as journal and pin portion of crankshaft, connecting rod, the cylinder, and piston. The splashed engine oil is provided to supply the cylinder head valve system by timing belt. OIL PRESSURE SWITCH SPRAY CRANKSHAFT OIL PUMP PLUG UNIT (OIL FILTER) Flow of oil CYLINDER HEAD CAM, VALVES ROCKER ARMS SPLASH PISTON CYLINDER OIL PURESSURE SWITCH CRANKSHAFT CONNECTING ROD LARGE END TIMING BELT SPRAY NOZZLE (M.B.C) OIL PAN SUCTION PIPE PLUG UNIT(OIL FILTER) OIL PUMP - 44 -
7-2 OIL SENSOR The oil sensor system is composed of the oil pressure switch and CPU (Central Processing Unit) inside of the Ignition coil. In accordance with the oil level which means oil pressure, the pressure switch functions ON and OFF. The type of pressure switch is normally closed ON type. Switching pressure: 0.10 through 0.20 kg/cm 2 (10 through 20KPa) While there is no pressure (No oil, or Low level), the diaphragm is pressed by the spring force, resulting the contact closes ON. When oil pressure increases, the diaphragm is pressed by the oil pressure which is bigger than the spring force, resulting the contact opens OFF. INSPECTION Measure resistance between the terminal and the pressure switch body. ON close the contact: 0 ohm (continuity) while engine stopped. OFF open the contact: (No continuity) during engine running. The switch structure is complicated, so if its function cannot be recovered even after cleaning, replace the switch with new one. Apply sealant (Three Bond 1215) to the thread on the pressure switch when re-assembling. - 45 -
7-3 BREATHER SYSTEM The Breather system functions to decrease for inside pressure of crankcase (in the case of four-stroke engines). The pressure becomes highly more than the outside atmospheric pressure from reasons as follows; Piston Comes down, Leak of combustion gases from piston rings, Expansion of internal air by increase of temperature, Steam of lubrication oil. Breather system prevents for oil leakage from the oil seals of the rotation parts and/or matching surface of the crankcase and the main bearing cover and so on. Breather system is consisted of labyrinthine passage structure and leaf valves, and separates the increased pressure which from lubrication oil and gas * in the crankcase. The oil is returned in the crankcase and the gas to the air cleaner to reduce the pressure. (* Blow by gas: Non-combustion gases including the air pollution element which cannot release to atmosphere. It is returned to the air cleaner and non-combustion gases burn again.) In rammer engines, a breather system is required complicated structure to separate oil and gas, reason why heavy vibration of up-and-down movement compared with stationary engines. Therefore, the ER12 rammer engine is adopted the design which overcame such a difficulty and becomes the high-performance with compact. C GAS to AIR CLEANER A OIL SHELTER PLATE GAS and OIL PASSAGE (I.D.8) C A B B BREATHER SYSTEM (for separating to oil and gas.) OIL SHELTER PLATE COMBUSTION AIR CLEANER LEAF VALVE LEAF VALVE (OIL) CRANK CASE BREATHER SYSTEM OIL to CRANKCASE PASSAGE (I.D.3) OIL and GAS OIL GAS - 46 -
8. MAGNETO 8-1 MAGNETO The SUBARU Engine uses are CDI. CPU magneto ignition system. (1) CDI. CPU (CDI : Capacitor Discharge Ignition. CPU : Central Processing Unit.) has the ignition coil outside the flywheel, which is the standard specification. (The flywheel is a specialized piece of equipment.) As for the lighting coil, the ignition coil is outside the flywheel and a lighting coil is inside. 8-2 INSPECTING THE MAGNETO If the engine does not start, has difficulty starting, or does not run smoothly, check the magneto for defects according to the following procedure: (1) Carefully check the high-tension cable for any damage or short circuiting. (2) Check the sparking. 1 Take the spark plug out of the cylinder head, connect the spark plug with the plug cap and ground it on the cylinder head or any other metallic part of the engine. (The gap between the electrodes of the spark plug should be between 0.6 mm and 0.7 mm). 2 Rotate the engine by pulling the recoil starter and check the spark plug gap for sparking. If the spark plug is sparking, check the intensity of the spark. (Before checking the spark plug, disconnect the primary wire from the connector.) 3 Next, disconnect the spark plug from the plug cap and check the end of the high-tension cable for sparking. - 47 -
9. WIRING DIAGRAM WIRING DIAGRAM Spark plug Ignition coil CDI, CPU Oil pressure switch (Oil sensor) Stop switch Flywheel CHECK THE IGNITION COIL Hgh tenstion code wire Round female terminal Flat female terminal Flat male terminal Core CDI CPU * Checking table for analogue circuit tester. (Ω) (R±20%) Analogue circuit tester Apply red needle of the circuit tester Apply black needle of the circuit tester 1 2 3 4 5 1-46k 40k 40k-46k 2-2k-3k 2k-3k 3 2k-3k - 0 4 45k-50k 40k - 35k-40k 5 2k-3k 0 - * Checking table for digital circuit tester. (Ω) (R±20%) Digital circuit tester Apply red needle of the circuit tester Apply black needle of the circuit tester 1 2 3 4 5 1-40k 2 17M-18M - 0 17M-18M 0 3 17M-18M 0-17M-18M 0 4-5 17M-18M 0 0 17M-18M - Digital multimeter SANWA PC500. - 48 -
10. AUTOMATIC DECOMPRESSION SYSTEM 10-1 FUNCTIONS AND CONSTRUCTION EX series engines employ an automatic decompression system as a standard feature. This enables easy starting of the engine, with lighter recoil pull. The automatic decompression system releases the compression of the engine by lifting up the exhaust valve at cranking speed. The following is the explanation of the function. At the end of the compression process, the release lever lifts up the rocker arm (exhaust) which in turn opens up the exhaust valve slightly to release the compression. The release lever has a flyweight on its end and another end of the lever is a crescent cam. When the engine is cranked, the crescent cam projects above the cam profile and lifts up the rocker arm (exhaust) because the force of the return spring on the weight is larger than the centrifugal force on the weight. ROCKER ARM (EXHAUST) ROCKER ARM (EXHAUST) RELEASE LEVER ROCKER ARM (INTAKE) RELEASE LEVER CAM CRESCENT CAM A RELEASE LEVER DETAIL A CAMSHAFT When the cranking speed reaches a specified r.p.m., the crescent cam is retracted under the cam profile because the centrifugal force applied to the flyweight becomes larger than the force of the return spring on the weight and thus it is shifted to the position shown in the illustration below. ROCKER ARM (EXHAUST) ROCKER ARM (EXHAUST) ROCKER ARM (INTAKE) CAM CRESCENT CAM A RELEASE LEVER DETAIL A CAMSHAFT 12-2 INSPECTION When assembling the release lever, make sure that it works smoothly. - 49 -
11. CARBURETOR 11-1 SPECIFICATIONS Float type A/C Type Single Main Jet # 66.3 Pilot Jet # 30 Venturi Bore (mm) φ12 11-2 FUNCTIONS AND CONSTRUCTION 11-2-1 FLOAT SYSTEM The float chamber is located below the carburetor body. Through the operation of the float and the needle valve, the float chamber maintains a constant fuel level while the engine is working. The fuel flows from the tank into the float chamber through the needle valve. When the fuel rises to a specific level, the float rises. When the buoyancy of the float is balanced with the fuel pressure, the needle valve shuts off the fuel passage, thereby maintaining the fuel at the predetermined level. 11-2-2 SLOW SYSTEM The slow system supplies fuel to the engine during idling and low-speed operation. Fuel is initially metered by the main get and then metered once again by the slow jet. The fuel / air mixture is fed to the engine through the pilot outlet and the bypass. During idling, fuel is fed to the engine mainly through the pilot outlet. 11-2-3 MAIN SYSTEM The main system feeds fuel to the engine at medium and high speed operation. Fuel is metered by the main jet and flows into the main nozzle. Air metered by the main air jet is mixed with fuel through the bleed holes of the main nozzle. The fuel/air mist is injected into the Venturi and mixed once again with air from the air cleaner. This fuel/air mixture is now of optimum concentration and is fed into the combustion chamber of the engine. 11-2-4 CHOKE SYSTEM The choke system is for easier start of the engine in cold weather conditions. When the engine is started with a closed choke, the negative pressure applied to the main nozzle increases. This causes a larger amount of fuel to be drawn into the carburetor, which in turn makes it easier to start the engine. - 50 -
11-3 FLOAT TYPE CARBURETOR 11-3-1 OPERATION AND CONSTRUCTION FLOAT SYSTEM The float chamber is located 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 closes to shut off the fuel, thereby keeping the fuel at the predetermined level. FUEL NEEDLE VALVE FLOAT Fig.11-1 PILOT OUTLET BY-PASS PILOT AIR JET MAIN NOZZLE PILOT JET AIR INTAKE CHOKE MAIN AIR JET FLOAT Fig.11-2 MAIN JET - 51 -
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 bypass. At idling speed, the fuel is mainly fed from the pilot outlet. MAIN SYSTEM The main system feeds the fuel to the engine at 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. CHOKE The choke is used for easy starting when the engine is cold. When the starter is operated with a closed choke, the negative pressure applied to the main nozzle increases and draws more fuel ; thus richening the mixture and making starting the engine easier. 11-3-2 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 1 9 10 2 11 12 3 6 7 8 4 24 5 be kept clean at all times. The carburetor disassembly and reassembly procedures are as follows. 16 THROTTLE SYSTEM (1) Remove the philips screw 1 and throttle valve 2, and pull out the throttle shaft 3. (2) The spring 4 can be taken out by removing the throttle stop screw 5. 19 18 17 21 15 14 23 22 20 *Be careful not to damage throttle valve rim. 13 Fig.11-3 - 52 -
CHOKE SYSTEM (1) Remove the philips screws 6 and choke valve 7, and pull out the choke shaft 8. (2) When reassembling the choke shaft, make sure that the cutout in the choke valve faces the pilot air jet. Meanwhile. when reassembling set the at the right position. PILOT SYSTEM (1) Remove the bolt 9 and plate 10. And then remove the pilot jet 11. (2) Reassembly Tighten the pilot jet securely. Otherwise, the fuel may leak, causing engine malfunction. MAIN SYSTEM (1) Remove the bolt 13 and take out float chamber body 15. (2) Remove the main jet 17 and guide holder 18 from the body. And then remove the main nozzle 19. (3) Reassembly a) Fasten the main jet and main nozzle securely to the body. Otherwise, the fuel may become too rich and cause engine malfunction. b) The bolt 13 tightening torque is 70 kg-cm. Be sure to set the gasket 16 and 14 for chamber 15. FLOAT SYSTEM (1) Pull out the float pin 20 and remove the float and then remove the clip and needle valve. If the needle valve needs to be replaced, replace it with rubber needle. (2) When removing the needle valve and float, gently tap the reverse side of the float pin 20 using a rod more slender than the float pin and remove, since the float pin is pressed into the carburetor body. 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. - 53 -