Rato R740 Service Manual
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Rato R740 Service Manual

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R740
Service Manual
Chongqing RATO Technology Co., Ltd.

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Summary of Contents for Rato R740

  • Page 1 R740 Service Manual Chongqing RATO Technology Co., Ltd.
  • Page 2 This Manual covers specifications that shall be followed in the process of regular maintenance and troubleshooting of generator sets. Make sure the equipment's maintenance staff can refer to this Manual at any time. This Manual describes correct methods to service this equipment. The Company does not undertake any liability for any personal casualty and equipment damage caused due to ignoring these rules.
  • Page 3 Safety Warnings The personal and property safety of you and others is very important. Please carefully read the three kinds of extremely important safety warnings that we have described in the Service Manual and on the decals of the generator sets. There is the symbol in front of each safety warning.

  • Page 4: Table Of Contents

    Contents Part I Introduction ........................1 1-1 Engine components ....................... 1 1-1-1 Structural features ...................... 1 1-1-2 Gasoline engine model and No.................. 2 1-2 Product parameters......................2 1-3 Service standards ......................3 Part II Maintenance ........................4 2-1 Maintenance list ......................4 2-2 Oil ..........................
  • Page 5 Disassembly and assembly ....................32 3-4-7 Starting control box ....................39 3-4-8 Starter motor ......................43 3-5 Electrical schematic diagram (electric starting type) ..........44 Appendix ..........................45...

  • Page 6: Part I Introduction

    Part I Introduction Part I Introduction 1-1 Engine components 1-1-1 Structural features Muffler Air filter Starting control box Radiator Fuel drain bolt Spark plug Oil level gauge Governing bracket Starter motor...

  • Page 7: Gasoline Engine Model And No

    Part I Introduction 1-1-2 Gasoline engine model and No. Model Finished product No. Serial No. 1-2 Product parameters Gasoline engine R740D Air-cooled, 4-Stroke, OHV, V-Twin Type of gasoline engine cylinder Displacement (cc) 739.3 Ignition system Transistor magnet ignition (contactless) Fuel tank volume (L) None ≤374 Minimum fuel consumption rate, g/kw.h...

  • Page 8: Service Standards

    Part I Introduction 1-3 Service standards Gasoline engine Part Item Standard Service limit Maximum no-load speed 3180-3800 rpm Gasoline engine Cylinder pressure 1.25MPa/1400rpm Cylinder Cylinder bore diameter 82mm 82.195mm Cylinder head Warping 0.10mm cover Outer diameter of piston skirt 81.962~81.98mm 81.86mm Piston-cylinder clearance 0.02~0.058mm...

  • Page 9: Part Ii Maintenance

    Part II Maintenance Part II Maintenance 2-1 Maintenance list Good maintenance is the best guarantee to realize safe, economical and zero-fault operation. It is also conducive to environmental protection. The exhaust gas of the engine contains toxic carbon monoxide. Please shut down the gasoline engine for maintenance.

  • Page 10: Air Filter

    ④ Install the oil dipstick. Fuel drain bolt Gasoline engine oil capacity: 1.6L for R740; 1.8L for the first use; 1.6L from the second use. Oil level upper limit Oil level lower limit General purpose oil SAE15W-40 SJ, or SAE10W-30 gasoline engine oil equivalent to API SJ.

  • Page 11: Spark Plug

    Part II Maintenance Cleaning the filter element with gasoline or flammable solvent may lead to fire or explosion. Please clean it with soapy water or nonflammable solvent. Do not start the generator without air filter, otherwise it will accelerate the wear of the gasoline engine.

  • Page 12: Adjustment Of Valve Clearance

    Part II Maintenance ①. Remove the spark plug cap. ②. Remove the spark plug with the spark plug socket wrench. ③. Visually inspect the spark plug insulator for damage. If the insulator is damaged, replace it with a new one. If the electrode has carbon deposits, clean it with a wire brush.
  • Page 13 Part II Maintenance Remove the cylinder head cover bolt and the Cylinder head cover bolt cylinder head cover. Remove the air director plate. Rotate the flywheel to align the mark on the flywheel with that of the air director. The No. 1 cylinder valve clearance can be adjusted.

  • Page 14: Governor

    Part II Maintenance 2-6 Governor Remove the air filter. Governing screw Unscrew the governing arm nut. Check whether the throttle lever is in the high speed position. When rotating the governing arm shaft counterclockwise, tighten the governing arm nut. Move the governor arm to the low speed position and check whether the throttle arm is in contact with the throttle stop screw.

  • Page 15: Part Iii Fault Judgement And Repair

    Part III Fault Judgement and Repair Part III Fault Judgement and Repair 3-1 Fault judgement 3-1-1 Start difficulty Phenomenon Cause Remedy No fuel in fuel tank Refuel Clogged venthole of fuel Dredge tank cap Main measuring hole is Impeded improperly adjusted or Re-adjust or clean, blow through fuel flow or blocked...

  • Page 16: Underpower

    Part III Fault Judgement and Repair If gasoline engine is still unable to be started, please send it to authorized dealer of the Company for overhaul. Spark detection (During the spark-over test of the spark plug) Ensure that there is no spilled fuel outside the gasoline engine and the spark plug is not soaked by fuel.

  • Page 17: Unstable Speed

    Part III Fault Judgement and Repair Remove the spark plug cap and the spark plug, and install the cylinder pressure gauge at the spark plug hole. Pull the starter for several times and measure the compression pressure. Atmospheric pressure in cylinder (≥1.25MPa/1300r) Pressure gauge 3-1-3 Unstable speed...

  • Page 18: Overheating Of General-Purpose Gasoline Engine

    Part III Fault Judgement and Repair 3-1-5 Overheating of general-purpose gasoline engine Phenomenon Cause Remedy Insufficient oil Fill sufficient oil Exhaust port is blocked Clean exhaust port Leakage of air director Repair damaged place Sundries blockage in the middle of cooling fins Clean cooling fins Gasoline engine Deformation of connecting rod causes the wears of the...

  • Page 19: Pre-Maintenance Preparations

    Part III Fault Judgement and Repair 3-2 Pre-maintenance preparations 3-2-1 Safety factors Failure of observing the following precautions will cause the void of warranty commitment provided with the engine, and it may damage the engine or cause personal injury. Therefore, before operating the engine, the user shall pay special attention to following points: 1) Strictly carry out the matching according to power shown on the nameplate.

  • Page 20: Special Tools

    Part III Fault Judgement and Repair 3-2-2 Special tools Tool name Application location·Remarks Inspection of oil level of the carburetor Float height gauge Disassembly and installation of valve guide Valve guide replacer Assembly of the ball bearing Outer seat ring assembler Installation of the handle on the assembler and installation of Assembler handle the bearing...

  • Page 21: Disassembly Chart

    Part IV Wiring Diagram 3-3 Disassembly chart Gasoline engine Flywheel Carburetor Ignition coil Air director Air filter Starting control box 3-4 Gasoline engine 3-4-1 Air director Engine Lift the fan guard decoration sheet up to take out it. First twist out the locking handle assembly.

  • Page 22: Impeller/Flywheel/Ignition Coil/Charging Coil

    Part IV Wiring Diagram 3-4-2 Impeller/flywheel/ignition coil/charging coil Flywheel Spark plug cap Flywheel bolt Impeller Ignition coil Bolt M6×30 Flywheel gasket Charging Impeller coil mounting Bolt M8×16 plate Stud Please fix the clip in the Bolt M6×30 slot during installation. Therefore, the parts in the figure are key components.
  • Page 23 Part IV Wiring Diagram Use the special tools to remove the flywheel, and do not use the hard objects to knock it to avoid damaging the flywheel. When the flywheel is removed, the semicircular key on the crankshaft may be brought out.
  • Page 24 Part IV Wiring Diagram Connect one detection wire to the wire end of the Spark plug cap spark plug cap, make the other detection wire contact with the spark plug end, and then measure the resistance of the spark plug cap. 10KΩ...

  • Page 25: Air Filter

    Part IV Wiring Diagram 3-4-3 Air filter Locking nut assembly of the air filter Air filter housing cover Air filter buckle Air filter element (foam) Air filter element (paper) Air filter gasket Locking handle assembly Bolt M6×35 Air intake pipe cover Air filter seat assembly Screw...
  • Page 26 Part IV Wiring Diagram you can go to authorized dealer of the Company to change the main metering hole and adjust the carburetor. Otherwise, the gasoline engine shall be used by reducing power. Even if being equipped with proper carburetor, every 300 m's rise in ASL will reduce the power of the gasoline engine by about 3.5%.
  • Page 27 Part IV Wiring Diagram Disassembly and assembly If any part of the air filter is handled improperly, dirt will enter the air intake system and thus damage the engine. Air filter connection pipe Bolt M6×65 Carburetor assembly Carburetor seal gasket Bolt M6×95 Bolt M6×30 Exhaust pipe...
  • Page 28 Part IV Wiring Diagram ② Use the straight screwdriver to unscrew the main nozzle to the right. For replacement of main nozzles, both main nozzles should be replaced. When disassembling the main nozzles, please place the carburetor in the same direction as the above figure.
  • Page 29 Part IV Wiring Diagram Idle metering hole O-ring Adjusting screw of mixing ratio Carburetor body Master nozzle Main metering hole Needle valve Float Spring Latch Screw Electron magnetic valve O-ring Fuel drain nozzle Before the installation of the carburetor, the fuel drain bolt must be unscrewed to drain off the fuel inside. No Open Flames.
  • Page 30 Part IV Wiring Diagram b) Clean thoroughly with compressed air before assembling. Main metering hole c) Clean thoroughly with compressed air before assembling. Master nozzle Before assembly, please confirm whether the oil cup sealing washer exists. f) Inspection Float height Place the carburetor as shown in the figure.

  • Page 31: Cylinder Head/Valve

    Part IV Wiring Diagram Tool: float height gauge Float height gauge 3-4-5 Cylinder head/valve Disassembly\assembly ① Remove the air filter ② Remove the air director ③ Remove the carburetor and heat insulation pad Sealing ring Air director of Valve lifter assembly cylinder block Shoulder bolt Bolt M6×10...
  • Page 32 Part IV Wiring Diagram Cylinder head Valve rocker arm shaft Valve rocker Cylinder head assembly arm shaft Valve locking screw Apply oil first during Exhaust valve installation Valve adjustment nut Apply oil first during installation Intake valve Valve spring seat Valve gutter Valve spring Oil deflector...
  • Page 33 Part IV Wiring Diagram Standard Maintenance limit 5.48mm (intake) 5.54mm (exhaust) 5.318mm (intake) 5.275mm (exhaust) ③ Free length of valve spring Measure free length of valve spring. If it is below the standard or exceeds service limits, replace the spring. Standard Maintenance limit 39.4mm...
  • Page 34 Part IV Wiring Diagram Exhaust valve side: knock the exhaust valve guide Valve guide until the retainer ring fully contacts the cylinder cover retainer ring Valve guide puller (as shown in the figure). The valve guide installation height is 1mm. Intake valve side: knock the intake valve guide to the specified height (measured from the top of the valve guide to the surface of the cylinder cover) (as shown...
  • Page 35 Part IV Wiring Diagram guide pipe: Subtract outer diameter of valve stem from corresponding inner diameter of valve guide pipe to obtain the clearance between valve guide pipe and valve stem. f) If the clearance between valve stem and valve guide exceeds maintenance limit, replace a new guide, to judge if the clearance can be within maintenance limit.

  • Page 36: Muffler

    Part IV Wiring Diagram Make sure that the contact width of valve seat completed is within specified range. Standard Maintenance limit 0.85mm 2.0mm e) Slightly grind by 45° grinder to remove any burr on the edge of valve seat. Valve f) After reshaping the valve seat, check the width grinding tool of valve seat.

  • Page 37: Disassembly And Assembly

    Appendix Disassembly and assembly Crankcase Locating Bolt M8×50 cover assembly Oil seal Bolt M8×55 Crankcase gasket Crankcase assembly...
  • Page 38 Appendix Crankcase cover assembly Crankcase cover Governing gear components Locating pin Oil level gauge Oil pump gasket assembly Oil pump cover Bolt M6×25 Bolt M6×20 Oil screen Steel ball Pressure relief Oil suction pipe valve spring Oil pump components...
  • Page 39 Appendix Crankcase assembly Cotter pin Bolt M6×20 Flat washer Negative Oil sensor pressure nozzle Oil seal Breathing plate assembly Governing Breathing tank gasket Breathing tank screen Bolt M6×30 Tension disc Breathing tank Oil seal gasket Breathing tank Crankcase cover plate Bolt M6×20 Flat washer Fuel drain bolt...
  • Page 40 Appendix Crankshaft/piston Piston assembly Balance shaft Piston assembly Connecting rod cover Connecting rod bolt Crankshaft Apply oil here. ① Installation Manufacturer's mark 120° a) Piston Make manufacturer's mark face up when assembling. Be careful not to confuse the Ring 1 ring 1 with the ring 2 (the ring 1 is chrome plated).
  • Page 41 Appendix b) Snap ring of piston pin Snap ring of piston pin Jack the front end at the piston groove, to clamp the other end with a nose plier, and mount it in the groove while turning. Make the opening of snap ring be away Notch from the notch of piston.
  • Page 42 Appendix Standard Service limit 16.992mm 16.954mm c) Piston-cylinder clearance The difference between the maximum diameter of the cylinder and the diameter of the piston skirt is the piston-cylinder clearance. This clearance must be inspected before and after repair. During inspection, put the piston upside down in the cylinder, put a thickness gauge with appropriate thickness between the pressure bearing surface of the piston skirt and the cylinder wall, and then pull out the thickness gauge.
  • Page 43 Appendix inspection while filing, until the clearance is proper. Standard Service limit Ring 1/ring 2 0.20-0.40mm 1.0mm Oil ring 0.15-0.35mm 1.0mm ③ Inspection of connecting rod When the connecting rod is bent, twisted, or the outer ring of the big end bearing pad and the small end bushing moves, or there is a crack on one side, it shall be scrapped and replaced with new one.

  • Page 44: Starting Control Box

    Appendix Cam height Exhaust 4.723mm 4.35mm Inspect the outer diameter of the camshaft journal. When it is less than the service limit, the camshaft should be replaced. Standard Maintenance limit 16mm 15.916mm Analysis on causes of camshaft wear and its impact on the performance of whole gasoline engine: The main cause for abnormal camshaft wear of the camshaft is poor lubrication, Factors such as low oil viscosity, many impurities and small circulating oil volume is unable to form complete oil film on the camshaft surface, to cause it to be in a state of high-speed dry friction, resulting in serious wear on the cam...
  • Page 45 Appendix Safety plate (5A) 6×12mm(2) Assembly: Special screw Control box Before installation, check whether it is about to burn out. Silicon rectifier Oil alarm device Assembly: Carry out installation by aligning the hole of the control panel. Control panel Control box mounting rack Locking nut Combination switch...
  • Page 46 Appendix b. Inspection ● Gasoline engine switch Check the conduction performance between the wire and the fan guard. Position of the gasoline engine switch Conduction performance Non-conduction Conduction ● Gasoline engine switch (with oil alarm device) Check the conduction performance between the black wire and the gasoline engine switch body. Position of the gasoline engine switch Conduction Non-conduction...
  • Page 47 Appendix Black/white Black/red White ● Oil alarm indicator Connect on the black/red and yellow wires of the oil alarm device. 6V battery or dry battery, make sure that the alarm indicator is on. Black/red - (+) of the battery Yellow - (-) of the battery ※...

  • Page 48: Starter Motor

    Appendix ● Silicon rectifier Check the conduction performance between the two terminals. It is normal in case of conduction in forward direction and non-conduction in the reverse direction. ● Reset switch With the switch in the "ON" state, confirm the conduction performance between the two terminals.

  • Page 49: Electrical Schematic Diagram (Electric Starting Type)

    Appendix 3-5 Electrical schematic diagram (electric starting type) Voltage regulator Red and Red and black black White Yellow Red and black Red and black Oil protector Deep green and Yellow White deep yellow Yellow Green Yellow Flywheel/charging Spark plug Carburetor Spark plug Oil sensor Battery...

  • Page 50: Appendix

    Appendix Appendix Torque table Item Thread specification Torque value (N·m) Cylinder head assembly M10×1.25×80 42±3 Fuel drain bolt M12×1.5×15 24±2 Flywheel assembly M12×1.25×35 110±5 Crankcase cover assembly M8×50 26±2 Connecting rod cover assembly M6×35 15±1 Cylinder head cover assembly 10±1 Spark plug assembly M14×1.25 28±2...
  • Page 51 Chongqing RATO Technology Co., Ltd. Address: Area B, Shuangfu Industrial Park, Jiangjin District, Chongqing Service hotline: 400-681-9981 Fax: 023-85553450 Postal code: 402247 Website: www.rato.cc E-mail: ratoservice@rato.cc(service consultation) parts@rato.cc (parts ordering)

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