Robin America EH025 Service Manual
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Robin America EH025 Service Manual

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SERVICE
MANUAL
Model
EH025/EH035
ENGINE
PUB-ES1740
Rev. 05/03

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Summary of Contents for Robin America EH025

  • Page 1 SERVICE MANUAL Model EH025/EH035 ENGINE PUB-ES1740 Rev. 05/03...
  • 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 2003 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 ........................5 3-1 THE SMALLEST AND LIGHTEST 4-STROKE ENGINE IN THE MARKET .....
  • Page 4 Section Title Page 8. CARBURETOR ......................43 8-1 OPERATION AND CONSTRUCTION ................43 8-2 DISASSEMBLY AND REASSEMBLY................44 9. RECOIL STARTER ....................47 9-1 HOW TO DISASSEMBLE ....................47 9-2 HOW TO REASSEMBLE ....................49 9-3 CHECK AFTER REASSEMBLE ..................50 9-4 OTHER GUIDES ......................50 10.

  • Page 5: Specifications

    1. SPECIFICATIONS MODEL EH025 EH035 Air-Cooled, 4-Cycle, Single-Cylinder, Type Horizontal P.T.O. Shaft, Gasoline Engine Bore x Stroke 34 x 27 mm (1.34 x 1.06 in.) 39 x 28 mm (1.54 x 1.10 in.) Piston Displacement 24.5 cm (1.49 cu.in.) 33.5 cm (2.04 cu.in.)

  • 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 EH025 ( 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 ) CLUTCH CHARACTERISTICS CLUTCH MEET 4000 5000 6000...
  • Page 8 EH035 ( Nm ) ( kg-m ) MAXIMUM TORQUE 0.18 0.16 ( PS ) ( kW ) 0.14 0.12 CONTINUOUS RATED HORSEPOWER RECOMMENDED HORSEPOWER RANGE (g/kWh ) ( g/PSh ) CLUTCH MEET 4000 5000 6000 7000 8000 4000 - 4400 r.p.m. Revolution (r.p.m.) - 4 -...

  • Page 9: Features

    3) Shorter shaft length at the output side (magneto side), by arranging the cam gear unit at the opposite side of the magneto. 4) Light weight construction, because of the resin made came gear, rocker cover and other parts.(EH025) And because of the resin made came gear, other parts.(EH035)
  • Page 10 (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 11 (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 12: 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 13: 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 14: Ignition System

    The carburetor is calibrated carefully for easy start- ing, good acceleration, low fuel consumption and sufficient output. Fig. 4-7 4-10 AIR CLEANER EH025 ELEMENT The air cleaner element is urethane foam (semi- wet type). This air cleaner has a compartment that separates blow-by gas from lubricant oil.

  • Page 15: 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 16: 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 - 12 -...
  • Page 17 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 - 13 -...

  • Page 18: Disassembly And Reassembly

    3) To prevent losing and misplacing, temporarily assemble each group of disassembled parts. 4) Carefully handle disassembled parts, and clean them with washing oil if necessary. 5) Use the correct tools in the correct way. 5-2 SPECIAL TOOLS (EH025 ONLY) Tool No. Tool...
  • Page 19 OIL GAUGE Fig. 5-3 Fig. 5-2 LEAD WIRE Fig. 5-4 M5 x 8 SCREW : 1 pce. EH025 EH035 STOP SWITCH PLUG COVER PLUG COVER STEP 1 STEP 1 M5 x 12 SCREW AND WASHER AY : 1 pce. ENGINE COVER...
  • Page 20 Step Parts to remove Remarks and procedures Fasteners Air cleaner, insulator, insulator Remove air cleaner cover and air M5 x 14 mm ; 1 pc. carburetor cleaner element. Remove fuel tube from carburetor, and then remove breather pipe and return pipe from cylinder. It is convenient to use a small-sized screwdriver to remove tubes.
  • Page 21 EH025 CHOKE PLATE CHOKE LEVER CARBURETOR AIR CLEANER PLATE PLATE O-RING M5 x 40 SCREW : 2 pcs. ELEMENT AIR CLEANER SPACER COVER BREATHER PIPE RETURN PIPE RETURN CHECK CHECK PIPE VALVE ( 1 ) Fig. 5-8 VALVE O-RING M5 x 14 SCREW...
  • Page 22 The muffler and the muffler cover are socket head bolt ; fastened together with two M5 x 40 mm 2 pcs. socket head bolts. M4 x16mm; 2 pcs. (EH025) Recoil starter Remove recoil starter from crankcase. M5 x14mm; 4 pcs. (EH035) Fuel tank Remove fuel tank from housing blower.
  • Page 23 Step Parts to remove Remarks and procedures Fasteners Blower housing Remove blower housing from cylinder M5 x18mm; 3 pcs. (EH025) and crankcase M5 x16mm; 4 pcs. (EH035) M6 x23mm; 2 pcs. (EH025) Clutch Remove the clutch from the flywheel. M8 x23.5mm; 2 pcs.
  • Page 24 Step Parts to remove Remarks and procedures Fasteners Flywheel 1) Remove flywheel from crankshaft. *Use the flywheel puller as shown in the Figure, and remove the fly- wheel by rotating the center shaft clockwise. Remove ignition coil from cylinder M4 x 20 mm ; Ignition coil block.
  • Page 25 Step Parts to remove Remarks and procedures Fasteners Oil case Remove oil case from crankcase. M5 x18 mm; Remove the oil case from the 4 pcs. recoil side of the crankcase, by tapping the oil case with a plastic or wooden hammer. Oil tube and Retainer plate Pull out the oil tube, by holding its base.
  • Page 26 Parts to remove Remarks and procedures Fasteners Rocker cover Remove rocker cover from cylinder M5 x 16mm ; 3 pcs. (EH025) block. M5 x 16mm ; 4 pcs. (EH035) Cam gear cover Remove cam gear cover from cylinder M5 x 14mm ; 3 pcs.
  • Page 27 Crankcase Remove the crankcase from the M5 x 14mm ; 8 pcs. cylinder block by tapping it with a (EH025) plastic or wooden hammer from the M5 x 16mm ; 4 pcs. recoil side. Take care not to lose the (EH035) check balls (2 pcs.) that are held by...
  • Page 28 Step Parts to remove Remarks and procedures Fasteners Valve, Valve spring and Hold the valve from the inner side of the Spring retainer cylinder, then push the spring retainer and remove it by sliding. SPRING RETAINER VALVE SPRING SPACER STEP 9 INTAKE VALVE EXHAUST VALVE Fig.
  • Page 29 Step Parts to remove Remarks and procedures Fasteners Piston and Piston ring Remove the two piston clips, take out the piston pin, and then remove the piston from the small end of the connecting rod. When removing the piston, take care to prevent dust from getting in the bearing at the connecting rod small end.

  • Page 30: 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 31 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 32 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 : 4.5 - 6.5 N ・...
  • Page 33 5-4-4 OIL CASE Install the lead valve with the cutout facing to the oil filling port. Tightening torque Retainer plate M4 x 10 mm hexagonal socket head M4 BOLT M5 SCREW bolt (1 pc.) 3 - 4 N・m 4 - 5.5 N・m Oil case M5 x 18 mm screw, and washer (4 pcs.) (30 - 40 kgf・cm) (40 - 55 kgf・cm)
  • Page 34 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 kgf ・...
  • Page 35 WASHER : 3 pcs. Installing the blower housing. Blower housing tightening torque M5 x 18 mm Screw : 3 pcs. (EH025) M5 x 16 mm Socket hesd bolt : 4 pcs. (EH035) Tightening torque : 4 - 5.5 N・ m (40 - 55 kgf ・...
  • Page 36 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. 5-42 (2) Install the cam lifter. ADJUSTING SCREW (3) Pass the push rod through the hole of the cyl- inder block.
  • Page 37 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 kgf ・...
  • Page 38 : 1 pce. PLATE Recoil tightening torque MUFFLER M4 x 16 mm screw : 2 pcs. (lower side) (EH025) GASKET, MUFFLER Tightening torque : 1 - 2.5 N・ m (10 - 25 kgf ・ cm) (0.7 - 1.8 ft ・ lb.)
  • Page 39 EH025 tighten them together. GASKET, INSULATOR, INSULATOR M5 x 18 mm screw : 2 pcs. (EH025, EH035) CARBURETOR INSULATOR M5 x 12 mm screw : 1 pc. (EH025, EH035) Tightening torque : 4 - 5.5 N ・ m (40 - 55 kgf ・ cm) (2.9 - 4.0 ft ・...
  • Page 40 Tightening torque : 0.5 - 1 N・ m (20 - 40 kgf ・ cm) (5 - 10 kgf ・ cm) (1.4 - 2.9 ft ・ lb.) (0.35 - 0.7 ft ・ lb.) EH035 EH025 GASKET, GASKET, CARBURETOR CARBURETOR CHOKE LEVER...
  • Page 41 (6.5 - 9.4 ft ・ lb.) 5-4-18 CLUTCH M6 BOLT : 2 pcs. (EH025) M8 BOLT : 2 pcs. (EH035) Install the clutch with the “ ← ”(EH025), “R”(EH035) mark on the clutch shoe at the front side (facing the assembly worker). SPRING Bolt (clutch) M6 x 23mm : 2 pcs.
  • Page 42 (2) Faston terminals (2 places) from the stop switch. (EH025) Either Faston terminal can be connected with the coil terminal. (EH025) Faston terminals (2 places) of the coil. (EH025) The cylinder side is the grounding terminal. (EH025) Fig. 5-56 ※ Install the engine cover by placing it on the...
  • Page 43 (4) Install the plug cover by hooking the lower claw on the engine cover first and then fitting its upper part. M5 x 12 mm screw (2 pcs.) (EH025,EH035) M5 x 8 mm screw (1 pce.) (EH035) Tightening torque : 2 - 4 N ・ m Tightening torque : 1.5 - 3 N ・...
  • Page 44 (1) Place the engine horizontally and fill oil from the oil filling port up to the threaded mouth. Use Robin genuine oil or engine oil class SF or higher. Oil capacity : EH025 0.08L (80 cc) EH035 0.10L (100 cc) (2) After filling oil, tighten the oil gauge.

  • Page 45: 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 46: 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 47: 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 48: 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 49 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 50 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 51: 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 52 (It the spiral spring escapes, put it in the case by following procedure shown in Fig. 9-6.) Untie the starter rope knot at the reel end and withdraw it to complete disassembling. EH025 SWING ARM REEL...

  • Page 53: 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 54: 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 55: 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 56: Engine Misfires

    10-1-3 IGNITION SYSTEM Check the followings for lack of spark. (1) Wires of the ignition coil, spark plug or contact breaker disconnected. (2) Ignition coil damaged and shorted. (3) Spark plug cable wet or soaked with oil. (4) Spark plug dirty or wet. (5) Spark plug electrode gap incorrect.

  • Page 57: 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 58: 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 59: Service Data

    12. SERVICE DATA 12-1 CLEARANCE DATA AND LIMITS Unit : mm (in) ITEM Limit CYLINDER * Valve guide inside dia. 3.005 - 3.025 EH025 (0.118 - 0.119) (0.122) 3.505 - 3.525 EH035 (0.138 - 0.139) (0.142) * Inside dia. 34.00 - 34.02 34.06...
  • Page 60 Unit : mm (in) ITEM Limit PISTON * Piston size (At skirt in thrust direction) 33.959 33.980 33.940 EH025 (1.3370 1.3378) (1.3362) 38.959 38.980 38.940 EH035 (1.5338 1.5346) (1.5331) * Ring groove side clearance 0.03 - 0.07 0.12 (0.0012 - 0.0028) (0.005)
  • Page 61 Unit : mm (in) ITEM Limit CAMSHAFT * Cam height (IN. and EX.) EH025 23.20 - 23.30 22.65 (0.9134 - 0.9173) (0.8917) EH035 * Journal outside dia. EH025 5.01 - 5.06 ----------- (0.1972 - 0.1992) EH035 EH025 4.99 - 5.00 ----------- (0.1965 - 0.1969)

  • Page 62: Torque Specifications

    12-2 TORQUE SPECIFICATIONS Tightening Torque ITEMS Kg-cm ft-lb. Retainer plate (Crankcase) 3 - 4 30 - 40 2.2 - 2.9 Cylinder block (Crankcase) 4.5 - 6.5 45 - 65 3.3 - 4.7 Oil case (Crankcase) 4 - 5.5 40 - 55 2.9 - 4.0 Cam gear cover 4 - 5.5...

  • Page 63: 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 20W-40 - 20 - 10 40 °C 104 °F - 59 -...

  • Page 64: 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 65: 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 n i l 13-5 ENGINE STORAGE (1) Perform the above 13-1 and 13-2 maintenance jobs. (2) Drain fuel from the fuel tank and carburetor. (3) To prevent rust in the cylinder bore, apply oil through the spark plug hole and turn the crankshaft several turns by hand.
  • Page 66 PRINTED IN THE USA...

This manual is also suitable for:

Eh035

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