Robin America EH025 Service Manual
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Robin America EH025 Service Manual

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SERVICE
MANUAL
Model
EH025
ENGINE
PUB-ES1460
Rev. 11/01

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  • Page 1 SERVICE MANUAL Model EH025 ENGINE PUB-ES1460 Rev. 11/01...
  • Page 2 940 Lively Blvd. • Wood Dale, IL 60191 • Phone: 630-350-8200 • Fax: 630-350-8212 e-mail: sales@robinamerica.com • www.robinamerica.com © Copyright 2001 Robin America, Inc.

  • Page 3: Table Of Contents

    CONTENTS Section Title Page 1. SPECIFICATIONS ....................... 1 2. PERFORMANCE ......................2 2-1 MAXIMUM OUTPUT ......................2 2-2 CONTINUOUS RATED OUTPUT ..................2 2-3 MAXIMUM TORQUE AND FUEL CONSUMPTION WITH MAXIMUM OUTPUT ..... 2 2-4 PERFORMANCE CURVES ..................... 3 3. FEATURES ........................4 3-1 THE SMALLEST AND LIGHTEST 4-STROKE ENGINE IN THE MARKET .....
  • Page 4 Section Title Page 8. CARBURETOR ......................41 8-1 OPERATION AND CONSTRUCTION ................41 8-2 DISASSEMBLY AND REASSEMBLY................42 9. RECOIL STARTER ....................45 9-1 HOW TO DISASSEMBLE ....................45 9-2 HOW TO REASSEMBLE ....................47 9-3 CHECK AFTER REASSEMBLE ..................48 9-4 OTHER GUIDES ......................48 10.

  • Page 5: Specifications

    1. SPECIFICATIONS - r i n i l , t f n i l n i l n i l e l i y t i ) . l e l i n i l y t i ) . l d i l l i o Specifications are subject to change without notice.

  • Page 6: Performance

    2. PERFORMANCE 2-1 MAXIMUM OUTPUT The maximum output is the output of an engine with its throttle valve fully opened under the condition that all the moving parts are properly broken in after the initial break-in period. A new engine may not produce full maximum output while its moving parts are still not broken-in.

  • Page 7: Performance Curves

    2-4 PERFORMANCE CURVES ( Nm ) ( kg-m ) MAXIMUM TORQUE 0.12 ( PS ) ( kW ) 0.10 0.08 0.06 CONTINUOUS RATED HORSEPOWER RECOMMENDED HORSEPOWER RANGE (g/kWh ) ( g/PSh ) 4000 5000 6000 7000 8000 Revolution (r.p.m.) - 3 -...

  • Page 8: Features

    3. FEATURES 3-1 THE SMALLEST AND LIGHTEST 4-STROKE ENGINE IN THE MARKET 1) Small-sized lubricant oil tank, thanks to the Robin original lubrication system. 2) Compact construction because of the optimum design, not taking any bore-up into consideration. 3) Shorter shaft length at the output side (magneto side), by arranging the cam gear unit at the opposite side of the magneto.
  • Page 9 (a) Since Robin lubricating system makes use of the pressure fluctuations in the crankcase, a lead valve is arranged at the lower part of the crankcase. By utilizing the negative pressure that occurs during the piston rising stroke, lubricant oil is supplied from the oil tube (located inside the oil tank, that is separated from the crankcase) to the crankcase, through the oil passage of the crankshaft which has rotary valve that opens and shuts with an appropriate timing.
  • Page 10 (b) When the engine is tilted muffler side down. In the same way as that of the carburetor side down, the return path in the rocker arm com- partment and the pressure relief hole operate and return the stagnant oil into the crankcase. (c) Engine tilted back and forth The breather hole located inside the rocker arm compartment is arranged approximately at the...

  • Page 11: General Description Of Engine Components

    4. GENERAL DESCRIPTION OF ENGINE COMPONENTS 4-1 CYLINDER BLOCK AND CRANKCASE The cylinder block and crankcase are aluminum die-castings split in upper and lower parts. The cylinder block and the cylinder head are a single piece. The valve seats are molded and the valve guides (intake valves and exhaust valves) and the valve stem seal (intake side only) are press fitted.

  • Page 12: Piston Rings

    4-4 PISTON RINGS The piston rings are made of special cast iron. The top ring is a barrel face type, the second ring is a tapered one, and the oil ring consists of three pieces, so as to reduce the oil consumption. BARREL RING SECOND...

  • Page 13: Ignition System

    4-8 IGNITION SYSTEM The ignition system is a TIC flywheel magneto type. The ignition timing is 25 degrees before the top dead center. The magneto consists of the flywheel and the ig- nition coil. The flywheel (that works as a cooling fan as well) is mounted on the crankshaft and the ignition coil is mounted directly on the cylinder block.

  • Page 14: Decompression System

    4-11 DECOMPRESSION SYSTEM The decompression equipment is installed inside the gear of the cam-gear unit. The decompres- CAMLIFTER sion equipment opens the intake valve before the compression top to relieve the compression pres- sure for easy start. WEIGHT CRESCENT CAM Fig.

  • Page 15: Sectional View Of Engine

    4-12 SECTIONAL VIEW OF ENGINE INTAKE VALVE EXHAUST VALVE BREATHER PIPE MUFFLER COVER CARBURETOR CLEANER MUFFLER CONNECTING CHECK BALL RETURN PIPE OIL GAUGE Fig. 4-10 - 11 -...
  • Page 16 ROCKER ARM SPARK PLUG PUSH ROD PISTON PISTON RING IGNITION COIL PISTON PIN FLYWHEEL CAM GEAR RECOIL STARTER OIL TUBE FUEL TANK Fig. 4-11 - 12 -...

  • Page 17: Disassembly And Reassembly

    5. DISASSEMBLY AND REASSEMBLY 5-1 PREPARATIONS AND SUGGESTIONS 1) When disassembling the engine, memorize the locations of individual parts so that they can be reassembled correctly. If you are uncertain of identifying some parts, it is suggested attach tags to them.

  • Page 18: Disassembly Procedures

    5-3 DISASSEMBLY PROCEDURES l i o l i o c t i c t i l i o i l p l l u . l i PLUG COVER STOP SWITCH ENGINE COVER STEP 1 OIL GAUGE Fig. 5-2 M5 SCREW AND WASHER : 2 pcs.
  • Page 19 n i l l l a s t i l l a CHOKE PLATE CHOKE LEVER CARBURETOR AIR CLEANER PLATE PLATE O-RING M5 SCREW : 2 pcs. AIR CLEANER ELEMENT SPACER COVER BREATHER PIPE RETURN CHECK PIPE VALVE ( 1 ) RETURN PIPE O-RING CHECK VALVE...
  • Page 20 l f f l f f l f f l f f l f f l i o e l l e l l . t f z i l e l l e l l c i l M5 SOKET HEAD BOLT : 2 pcs.
  • Page 21 n i l y l f BLOWER HOUSING M5 SCREW AND WASHER : 3 pcs. M6 BOLT, CLUTCH : 2 pcs. STEP 4 SPRING CLUTCH Fig. 5-11 - 17 -...
  • Page 22 y l f . t f y l f l l u f l i n i l l i o i l y SPARK PLUG STEP 5 IGNITION COIL M4 SCREW AND WASHER : 2 pcs. FLYWHEEL WASHER M6 BOLT AND Fig.
  • Page 23 c i t l l u l i o s t i l i o l l a OIL TUBE Fig. 5-15 LEAD VALVE RETAINER PLATE GASKET, CASE OIL TUBE M4 SOCKET HEAD OIL WEIGHT BOLT : 1 pce. OIL CASE STEP 6 M5 SCREW AND Fig.
  • Page 24 n i l n i l f i l t i s t f i l , t f f i l , t f , t f , t f . t f ROCKER ARM M5 SCREW AND WASHER : 3 pcs. ADJUSTING SCREW ROCKER COVER PUSH ROD...
  • Page 25 n i l c i t s l l n i l n i l Fig. 5-19 CYLINDER BLOCK STEP 8 CRANKSHAFT CRANKCASE M5 SOCKET HEAD BOLT : 6 pcs. Fig. 5-18 M5 SOCKET HEAD BALL BOLT : 2 pcs. - 21 -...
  • Page 26 n i l d i l SPRING RETAINER VALVE SPRING SPACER STEP 9 INTAKE VALVE EXHAUST VALVE Fig. 5-20 Fig. 5-21 - 22 -...
  • Page 27 p i l l l a l l a PISTON RING CLIP PISTON PIN PISTON CLIP STEP 10 CRANKSHAFT Fig. 5-22 - 23 -...

  • Page 28: Reassembly Procedures

    5-4 REASSEMBLY PROCEDURES PRECAUTIONS FOR REASSEMBLY 1) Clean parts thoroughly before reassembly. Pay most attention to cleanliness of piston, cylinder, crankshaft, connecting rod and bearings. 2) Scrape off all carbon deposits from cylinder head, piston top and piston ring grooves. 3) Check lip of oil seals.
  • Page 29 5-4-2 CONNECTING ROD, PISTON AND PISTON RINGS Install the piston on the connecting rod (1) After installing the piston rings, apply 4-cycle engine oil to the rings. NOTE ; Install the top ring and the second ring with their open ends displaced by 180 degrees. When installing a new ring, place the white mark at the right-hand side, and when reassembling a used one, install it with the contact face down.
  • Page 30 5-4-3 CYLINDER BLOCK AND CRANKCASE Installing cylinder block and crankcase Make sure that the liquid packing (Three Bond 1216) is evenly applied on the crankcase before installing the cylinder block. Tightening torque of the hexagonal socket head bolts (8 pce.) of the lower part of the crankcase : Tightening torque : 5 - 6.5 N m (50 - 65 kg cm) (3.6 - 4.7 ft lb.)
  • Page 31 5-4-4 OIL CASE Install the lead valve with the cutout facing to the oil filling port. Retainer plate M4 x 10 mm hexagonal socket head bolt (1 pc.) Oil case M5 x 18 mm screw, and washer (4 pcs.) OIL CASE M5 SCREW AND WASHER : 4 pcs.
  • Page 32 5-4-5 FLYWHEEL Installing the flywheel Degrease the crankshaft and the tapered portion of the flywheel perfectly when installing them. Align the flywheel key with the crankshaft key groove. Flywheel tightening bolt M6 x 16 mm, with spring washer : Tightening torque : 9 - 12 N m (90 - 120 kg cm) (6.5 - 8.8 ft lb.) Fig.
  • Page 33 5-4-7 BLOWER HOUSING M5 SCREW AND BLOWER HOUSING WASHER : 3 pcs. Installing the blower housing. Blower housing tightening torque M5 x 16 mm screw (3 pcs.) Tightening torque : 4 - 5.5 N m (40 - 55 kg cm) (2.9 - 4.0 ft lb.) Fig.
  • Page 34 5-4-9 PUSH ROD, CAMLIFTER AND ROCKER ARM Installing the push rod, cam lifter and rocker arm APPLY A SUFFICIENT AMOUNT OF OIL (1) Apply sufficient oil in the rocker shaft hole. Fig. 5-39 (2) Install the cam lifter. ADJUSTING SCREW (3) Pass the push rod through the hole of the cyl- inder block.
  • Page 35 5-4-10 CAMGEAR COVER Installing the cam gear cover CAMGEAR COVER Before installing the cam gear cover, apply oil on the camgear and the cam lifter sliding surface. Camgear cover tightening torque M5 x 14 mm screw (3 pcs.) Tightening torque : 4 - 5.5 N m (40 - 55 kg cm) (2.9 - 4.0 ft lb.) NYLON WASHER...
  • Page 36 5-4-12 ROCKER COVER Before installing the rocker cover, apply oil on the sliding surfaces of the rocker arm and the valve M5 SCREW AND ROCKER COVER stems. WASHER : 3 pcs. Rocker cover tightening torque M5 x 16 mm screw (3 pcs.) GASKET, Tightening torque : 4 - 5.5 N m ROCKER COVER...
  • Page 37 5-4-15 INSULATOR AND INSULATOR CARBURETOR Cover the insulator on the insulator carburetor and GASKET, tighten them together. INSULATOR M5 x 18 mm screw (2 pcs.) INSULATOR Tightening torque : 4 - 5.5 N m (40 - 55 kg cm) (2.9 - 4.0 ft lb.) NOTE : The end face of the adjustment screw shall be INSULATOR,...
  • Page 38 5-4-16 CARBURETOR AND AIR CLEANER (1) Assemble the plate, choke plate, air cleaner plate, carburetor, gasket carburetor, spacer, o-ring, breather pipe and return pipe. NOTE : When installing the choke plate, keep the choke lever fully closed. (lever touching the upper stopper). Apply grease or silicone on the choke plate after installing it.
  • Page 39 (b) Connect the fuel tank tube to the fuel joint of BREATHER PIPE the carburetor. (Check the bent of the tube). HOSE CLAMP AIR CLEANER PLATE (c) Connect the return pipe to the pipe joint at the UPPER CLAW center of the cylinder. (d) Connect the breather pipe to the pipe on the RETURN rocker cover and fasten it with the hose clamp.
  • Page 40 5-4-19 ENGINE COVER, STOP SWITCH AND PLUG COVER Installing the engine cover, stop switch and plug cover. (1) Assemble the stop switch on the engine cover in advance. Connect the stop switch wire to the terminal of the switch. (2) Faston terminals (2 places) from the stop switch.
  • Page 41 (4) Install the plug cover by hooking the lower claw PLUG COVER STOP SWITCH on the engine cover first and then fitting its upper part. M5 x 10 mm screw (2 pcs.) ENGINE Tightening torque : 2 - 4 N m COVER (20 - 40 kg cm) (1.4 - 2.9 ft lb.)
  • Page 42 5-4-20 ENGINE OIL, OIL GAUGE (1) Place the engine horizontally and fill oil from the oil filling port up to the threaded mouth. The oil capacity is approximately 0.08 liter. Use Robin genuine oil or engine oil class SF or higher.

  • Page 43: Magneto

    6. MAGNETO 6-1 FLYWHEEL MAGNETO The ignition system of the EH025 is the T.I.C. (Transistor, Igniter, Circuit) point less ignition system. 6-2 IGNITION OF MAGNETO When the engine does not start, has difficulty in starting or does not run correctly, carry out the following checks for magneto failure.

  • Page 44: Automatic Decompression System

    7. AUTOMATIC DECOMPRESSION SYSTEM 7-1 FUNCTIONS AND MECHANISM The decompression system is installed on the cam in order to open the intake valve and relieve the compression pressure at the first half of the engine compression cycle. The flyweight installed inside the cam gear has an appropriate shape (weight) to have the effect of the centrifugal force, and the end of the rotary shaft has a crescent cam shape.

  • Page 45: Carburetor

    8. CARBURETOR 8-1 OPERATION AND CONSTRUCTION 8-1-1 FUNCTIONS AND CONSTRUCTION OF THE DIAPHRAGM SYSTEM This engine is equipped with a diaphragm type carburetor. Since the fuel level is kept constant, irrespective of the tilting angle of the engine, it can be operated at any position.

  • Page 46: Disassembly And Reassembly

    8-2 DISASSEMBLY AND REASSEMBLY Fig. 8-2 1. Screw 9. Jet 17. Inlet needle valve 2. Plug 10. Gasket, pump 18. Metering lever 3. Swivel 11. Diaphragm, pump 19. Screw, metering lever pin 4. Washer 12. Spring, pump 20. Metering diaphragm gasket 5.
  • Page 47 8-2-1 PRECAUTIONS (1) Wash the carburetor with clean gasoline before disassembly. (2) Disassemble and reassemble the carburetor by referring to the exploded view. (3) Refrain from disassembling the throttle valve assy. (6), pump body assy. (13) and the main body. 8-2-2 DISASSEMBLY AND REASSEMBLE PROCEDURES (1) Removes the screw (25) and the primer pump cover (24).
  • Page 48 8-2-4 MARKS ON THE CARBURETOR Marks are stamped as shown in the figure at the right. 1 1 1 1 1 Model No. 2 2 2 2 2 Date of manufacture Example 1 1 1 1 1 : 116 ---------- WYL116 (Walbro model No.) 2 2 2 2 2 : 914 week 14 (May.

  • Page 49: Recoil Starter

    9. RECOIL STARTER 9-1 HOW TO DISASSEMBLE The recoil starter rarely have problem under normal use. When it fails, however, or when greasing, disassemble and reassemble it according to the following procedure. Tools : Screwdriver and pincers (pliers) (1) Remove the recoil starter from the engine. (2) Pull out the starter knob, hold the rotary reel with your thumb as shown in Figure 9-1 when the reel notch gets aligned with the starter rope...
  • Page 50 (3) Remove the parts as shown in Fig. 9-2. Remove the reel slowly while turning it back and forth gently, otherwise the spiral spring may escase from the case which may invite danger. (It the spiral spring escapes, put it in the case by following procedure shown in Fig.

  • Page 51: How To Reassemble

    9-2 HOW TO REASSEMBLE (1) Pass the starter rope through the starter knob and make an overhand knot as shown in Fig. 9-3. Pass the opposite side of the starter rope from the starter case to the reel, and make a knot in the same way, then put the rope end securely into the rope housing in the reel.

  • Page 52: Check After Reassemble

    9-3 CHECK AFTER REASSEMBLE (1) Pull the starter knob a few times to check if: A. The starter knob is too heavy to pull, check that each part has been assembled as specified. B. The ratchet fails to function, check is parts such as friction spring have been missing. (2) Pull out the starter knob to extend the rope to its extreme to see if: A.

  • Page 53: Troubleshooting

    10. TROUBLESHOOTING The following three conditions must be fulfilled for satisfactory engine start. 1. The cylinder filled with a proper fuel-air mixture. 2. Good compression in the cylinder. 3. Good spark, properly timed, to ignite the mixture. The engine cannot be started unless these three conditions are met. There are also other factors which make engine start difficult, e.

  • Page 54: Engine Misfire

    (4) Incorrect Valve 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. Clean or replace the parts.

  • Page 55: Engine Overheats

    10-4 ENGINE OVERHEATS (1) Crankcase oil level low. Add oil immediately. (2) Spark timing incorrect. (3) Low grade gasoline is used, or engine is overloaded. (4) Cooling air circulation restricted. (5) Cooling air path misdirected causes loss of cooling efficiency. (6) Cylinder head cooling fins clogged up with dirt.

  • Page 56: Installation

    11. INSTALLATION Engine life, ease of maintenance and inspection, frequency of checks and repairs, and operating cost all depend on the way in which the engine is installed. Review the following instructions carefully for install- ing the engine. 11-1 INSTALLING When mounting the engine, carefully examine its position, the method of connecting it to a machine, the foundation, and the method of supporting the engine.

  • Page 57: Service Data

    12. SERVICE DATA 12-1 CLEARANCE DATA AND LIMITS Unit : mm (in) - 53 -...
  • Page 58 Unit : mm (in) t r i - 54 -...
  • Page 59 Unit : mm (in) t f i l - 55 -...

  • Page 60: Torque Specifications

    12-2 TORQUE SPECIFICATIONS l - t n i l l i o l f f l f f e l l - 56 -...

  • Page 61: Oil Grade Chart

    12-3 OIL GRADE CHART Use oil classified SF or higher. Multi-grade oil tends to increase its consumption at high ambient temperature. Comparison between oil viscosity and temparature Single grade Specified Lubricant Quality 10W-30 Multi- grade 10W-40 40 °C - 20 - 10 104 °F - 57 -...

  • Page 62: Maintenance And Storage

    13. MAINTENANCE AND STORAGE 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 dur- ing 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.

  • Page 63: Every 100-200 Hrs. (Monthly) Maintenance

    13-4 EVERY 100-200 HRS. (MONTHLY) MAINTENANCE t l i f n i l t r i . f f 13-5 EVERY 500-600 HRS. MAINTENANCE s t i 13-6 EVERY 1000 HRS. (YEARLY) MAINTENANCE n i l 13-7 ENGINE STORAGE (1) Perform the above 13-1 and 13-2 maintenance jobs. (2) Drain fuel from the fuel tank and carburetor.
  • Page 64 PRINTED IN THE USA...

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