RH255, RH265 Service Manual IMPORTANT: Read all safety precautions and instructions carefully before operating equipment. Refer to operating instruction of equipment that this engine powers. Ensure engine is stopped and level before performing any maintenance or service.
Safety SAFETY PRECAUTIONS WARNING: A hazard that could result in death, serious injury, or substantial property damage. CAUTION: A hazard that could result in minor personal injury or property damage. NOTE: is used to notify people of important installation, operation, or maintenance information. WARNING Explosive Fuel can cause fires and severe burns. Do not fill fuel tank while engine is hot or running. Gasoline is extremely flammable and its vapors can explode if ignited.
Maintenance MAINTENANCE INSTRUCTIONS WARNING Accidental Starts can cause severe injury or death. Disconnect and ground spark plug lead(s) before servicing. Before working on engine or equipment, disable engine as follows: 1) Disconnect spark plug lead(s). 2) Disconnect negative (–) battery cable from battery.
Maintenance OIL RECOMMENDATIONS All-season KOHLER® PRO 10W-50 Synthetic Oil is the ideal oil for KOHLER engines. It is specifically formulated to extend the oil change interval to 300 Hours. Contact your Kohler authorized dealer for availability. 300-Hour oil change intervals are exclusive to and only authorized on KOHLER engines that utilize the KOHLER PRO 10W-50 Synthetic Oil. Alternative engine oils may be used with KOHLER engines but require 100-Hour oil change intervals for proper maintenance.
Specifications Engine Dimensions Dimensions in millimeters. Inch equivalents shown in [ ]. 10.50 [0.413] FUEL CAP REMOVAL 329.53 [12.974] 297.37 [11.707] 65.05 [2.561] 32.53 [1.281] 106.00 [4.173] METRIC FLANGE: 4X M8 X 1.25-6H 15.00 [0.591] 15.00 [0.591] SAE FLANGE: 4X 5/16-24 UNF-2B 32.53 [1.281] 65.05 [2.561] 66.00 [2.598] 162.00 [6.378] 15.24 [0.600] 4.74 [0.187] 3/4” STRAIGHT SHAFT SAE Ø 19.0 [0.75] Ø 19.0 [0.75] 24.5 5/16-24 UNF-2B 61.24 [2.411] MOUNTING FACE 242.84 [9.
Specifications ENGINE IDENTIFICATION NUMBERS Kohler engine identification numbers (model, specification and serial) should be referenced for efficient repair, ordering correct parts, and engine replacement. Model . . . . . . . . . . . . . . . . . . . . . RH265 2000 Series Engine Numerical Designation Specification . . . . . . . . . . . . . . . RH265-0001 Serial . . . . . . . . . . . . . . . . . . . . .
Specifications TORQUE SPECIFICATIONS3,5 RH255, RH265 Fuel Tank Mounting Screw Outlet Filter Fitting 4.5 N·m (40 in. lb.) 2.0 N·m (17.7 in. lb.) Governor Arm Nut Throttle Control Lever Nut 7 N·m (62 in. lb.) 4.5-6 N·m (40-53 in. lb.) Ignition Spark Plug Module Fastener 27 N·m (20 ft. lb.) 8 N·m (70.8 in. lb.) Muffler M6 Exhaust Screw 9.5 N·m (84 in. lb.) Rocker Arm Stud Pivot Jam Nut 24 N·m (212 in. lb.) 10 N·m (88.5 in. lb.) Valve Cover Fastener 8 N·m (70.8 in. lb.
Specifications CLEARANCE SPECIFICATIONS3 RH255, RH265 Crankcase Governor Cross Shaft Bore I.D. New Max. Wear Limit 6.000/6.018 mm (0.2362/0.2369 in.) 6.037 mm (0.2377 in.) Crankshaft End Play (free) Bore (in crankcase) New Bore (in closure plate) New Flywheel End Main Bearing Journal O.D. O.D.-New O.D.-Max. Wear Limit Max. Taper Max. Out-of-Round Closure Plate End Main Bearing Journal O.D. O.D.-New O.D.-Max. Wear Limit Max. Taper Max. Out-of-Round Connecting Rod Journal O.D. O.D.-New O.D.-Max.
Specifications CLEARANCE SPECIFICATIONS3 RH255, RH265 Ignition Spark Plug Gap Module Air Gap 0.76 mm (0.030 in.) 0.254 mm (0.0100 in.) Piston, Piston Rings, and Piston Pin Piston-to-Piston Pin Running Clearance Piston Pin Bore I.D. New Max. Wear Limit Piston Pin O.D. New Max. Wear Limit Top Compression Ring Side Clearance New Bore Used Bore (max.) Center Compression Ring Side Clearance New Bore Used Bore (max.) Top Compression Ring End Gap New Bore Used Bore (max.
Specifications CLEARANCE SPECIFICATIONS3 RH255, RH265 Valves and Valve Lifters Intake Valve Stem-to-Valve Guide Running Clearance Exhaust Valve Stem-to-Valve Guide Running Clearance Intake Valve Stem O.D. New Max. Wear Limit Exhaust Valve Stem O.D. New Max. Wear Limit Intake Valve Stem to Guide New Max. Wear Limit Exhaust Valve Stem to Guide New Max. Wear Limit Valve Guide Reamer Size Standard Intake Standard Exhaust Valve Seat Width Nominal Valve Face Angle 3 0.020/0.044 mm (0.008/0.0017 in.) 0.030/0.
Specifications GENERAL TORQUE VALUES English Fastener Torque Recommendations for Standard Applications Bolts, Screws, Nuts and Fasteners Assembled Into Cast Iron or Steel Grade 2 or 5 Fasteners Into Aluminum Size Grade 2 Tightening Torque: N·m (in. lb.) ± 20% 8-32 2.3 (20) 10-24 3.6 (32) 10-32 3.6 (32) 1/4-20 7.9 (70) 1/4-28 9.6 (85) 5/16-18 17.0 (150) 5/16-24 18.7 (165) 3/8-16 29.4 (260) 3/8-24 33.9 (300) Grade 5 Grade 8 2.8 (25) 4.5 (40) 4.5 (40) 13.0 (115) 15.8 (140) 28.3 (250) 30.
Tools and Aids Certain quality tools are designed to help you perform specific disassembly, repair, and reassembly procedures. By using these tools, you can properly service engines easier, faster, and safer! In addition, you’ll increase your service capabilities and customer satisfaction by decreasing engine downtime. Here is a list of tools and their source. SEPARATE TOOL SUPPLIERS Kohler Tools Contact your local Kohler source of supply. SE Tools 415 Howard St.
Tools and Aids TOOLS Description Hose Removal Tool, Dual Size/End (also available in EFI Service Kit) Used to properly remove fuel hose from engine components. Hydraulic Valve Lifter Tool For removing and installing hydraulic lifters. Ignition System Tester For testing output on all systems, including CD. Inductive Tachometer (Digital) For checking operating speed (RPM) of an engine. Offset Wrench (K and M Series) For removing and reinstalling cylinder barrel retaining nuts.
Tools and Aids FLYWHEEL HOLDING TOOL ROCKER ARM/CRANKSHAFT TOOL A flywheel holding tool can be made out of an old junk flywheel ring gear and used in place of a strap wrench. 1. Using an abrasive cut-off wheel, cut out a six tooth segment of ring gear as shown. 2. Grind off any burrs or sharp edges. 3. Invert segment and place it between ignition bosses on crankcase so tool teeth engage flywheel ring gear teeth.
Troubleshooting TROUBLESHOOTING GUIDE When troubles occur, be sure to check simple causes which, at first, may seem too obvious to be considered. For example, a starting problem could be caused by an empty fuel tank. Some general common causes of engine troubles are listed below and vary by engine specification. Use these to locate causing factors. Engine Cranks But Will Not Start ● Battery connected backwards. ● Blown fuse. ● Carburetor solenoid malfunction. ● Choke not closing.
Troubleshooting Engine Loses Power ● Dirty air cleaner element. ● Engine overheated. ● Excessive engine load. ● Restricted exhaust. ● Faulty spark plug(s). ● High crankcase oil level. ● Incorrect governor setting. ● Low battery. ● Low compression. ● Low crankcase oil level. ● Quality of fuel (dirt, water, stale, mixture). Engine Uses Excessive Amount of Oil ● Loose or improperly torqued fasteners. ● Blown head gasket/overheated. ● Breather reed broken. ● Clogged, broken, or inoperative crankcase breather.
Troubleshooting CRANKCASE VACUUM TEST WARNING Carbon Monoxide can cause severe nausea, fainting or death. Avoid inhaling exhaust fumes. Never run engine indoors or in enclosed spaces. Engine exhaust gases contain poisonous carbon monoxide. Carbon monoxide is odorless, colorless, and can cause death if inhaled. WARNING Rotating Parts can cause severe injury. Stay away while engine is in operation. Keep hands, feet, hair, and clothing away from all moving parts to prevent injury.
Troubleshooting COMPRESSION TEST For Command Twins: A compression test is best performed on a warm engine. Clean any dirt or debris away from base of spark plug(s) before removing them. Be sure choke is off, and throttle is wide open during test. Compression should be at least 160 psi and should not vary more than 15% between cylinders. All other models: These engines are equipped with an automatic compression release (ACR) mechanism.
Air Cleaner/Intake AIR CLEANER These systems are CARB/EPA certified and components should not be altered or modified in any way. Air Cleaner Components A B C D E F NOTE: Operating engine with loose or damaged air cleaner components could cause premature wear and failure. Replace all bent or damaged components. NOTE: Paper element cannot be blown out with compressed air. Unhook latch and remove air cleaner cover. Paper Element: Remove and replace paper element.
Fuel System Typical carbureted fuel system and related components include: ● Fuel tank. ● Fuel lines. ● Fuel tank filter (outlet fitting). ● Carburetor. Fuel tank outlet is located above carburetor inlet, allowing gravity to feed fuel through in-line filter and fuel line to carburetor. Fuel then enters carburetor float bowl. Fuel is drawn into carburetor body and is mixed with air. This fuel-air mixture is then burned in engine combustion chamber. FUEL RECOMMENDATIONS Refer to Maintenance.
Fuel System CARBURETOR WARNING Explosive Fuel can cause fires and severe burns. Do not fill fuel tank while engine is hot or running. These engines are equipped with a fixed main jet carburetor. Carburetor is designed to deliver correct fuelto-air mixture to engine under all operating conditions. Idle mixture is set at factory and cannot be adjusted. Typical One-Barrel Carburetor Components A Gasoline is extremely flammable and its vapors can explode if ignited.
Fuel System Troubleshooting-Carburetor Related Causes Condition Engine starts hard, runs rough, or stalls at idle speed. Engine runs rich (indicated by black, sooty exhaust smoke, misfiring, loss of speed and power, governor hunting, or excessive throttle opening). Engine runs lean (indicated by misfiring, loss of speed and power, governor hunting, or excessive throttle opening). Fuel leaks from carburetor. Possible Cause Low idle speed improperly adjusted.
Fuel System Carburetor Servicing WARNING Accidental Starts can cause severe injury or death. Disconnect and ground spark plug lead(s) before servicing. Before working on engine or equipment, disable engine as follows: 1) Disconnect spark plug lead(s). 2) Disconnect negative (–) battery cable from battery. High Altitude Operation Engines may require a high altitude carburetor kit to ensure correct engine operation at altitudes above 1219 meters (4000 ft.).
Governor System GOVERNOR Governor Components A J I I C E F K H D G B A Control Assembly B Nut C Governor Spring D Throttle Link E Dampening Spring F Throttle Control Lever G Governor Lever H Cup I Washer J Governor Gear K Governor Gear Shaft Governed speed setting is determined by position of throttle control. It can be variable or constant, depending on engine application. Governor is designed to hold engine speed constant under changing load conditions.
Lubrication System These engines use a splash lubrication system, supplying necessary lubrication to crankshaft, camshaft, connecting rod and valve train components. Lubrication Components A B C A Dipstick/Oil Fill Plug C B Oil Fill Plug (Optional) OIL RECOMMENDATIONS Refer to Maintenance. CHECK OIL LEVEL NOTE: To prevent extensive engine wear or damage, never run engine with oil level below or above operating range indicator on dipstick. Ensure engine is cool.
Electrical System SPARK PLUGS CAUTION Electrical Shock can cause injury. Do not touch wires while engine is running. Spark Plug Component and Details Inspection Inspect each spark plug as it is removed from cylinder head. Deposits on tip are an indication of general condition of piston rings, valves, and carburetor. Normal and fouled plugs are shown in following photos: Normal A B Plug taken from an engine operating under normal conditions will have light tan or gray colored deposits.
Electrical System ELECTRONIC IGNITION SYSTEM Inductive Discharge Ignition System Components Carbon Fouled J I F H B Soft, sooty, black deposits indicate incomplete combustion caused by a restricted air cleaner, over rich carburetion, weak ignition, or poor compression. Overheated C D E A G Position B A Kill Switch/Off of Switch Chalky, white deposits indicate very high combustion temperatures. This condition is usually accompanied by excessive gap erosion.
Electrical System Electronic Ignition System Tests 1. Disconnect cap from spark plug and attach it to terminal end of spark tester. Attach tester spring clip to a good ground, not to spark plug. Turn ignition switch ON and crank engine while observing firing tip of tester. Condition Tester is firing. Conclusion Ignition system is good. Install a new spark plug and try to start engine. If it still will not start, check other possible causes (fuel, compression, etc.). Tester doesn't fire.
Electrical System Wiring Diagram-3 Amp Charging System, Rectified Only C A B H E D G I F A Diode B Stator C Ignition Module D Spark Plug E Ignition Switch F Starter Motor G Relay H Battery Fuse I 12 Volt Battery 18 690 06 Rev. B KohlerEngines.
Electrical System Wiring Diagram-10 Amp Charging System, with Rectifier-Regulator A D C B H E I G F A Rectifier-Regulator B Stator C Ignition Module D Spark Plug E Ignition Switch F Starter Motor G Relay H Battery Fuse I 12 Volt Battery 30 KohlerEngines.com 18 690 06 Rev.
Electrical System 3/10 Amp Battery Charging Systems NOTE: Zero ohmmeters on each scale to ensure accurate readings. Voltage tests should be made with engine running at 3600 RPM - no load. Battery must be fully charged. Check specific gravity of battery. If low, recharge or replace battery as necessary. To test charging system for no charge to battery: 1. Separate bullet connector in white lead from rectifierregulator. Connect an ammeter from female terminal to positive (+) terminal of battery.
Starter System NOTE: Do not crank engine continuously for more than 10 seconds. Allow a 60 second cool down period between starting attempts. Failure to follow these guidelines can burn out starter motor. NOTE: If engine develops sufficient speed to disengage starter but does not keep running (a false start), engine rotation must be allowed to come to a complete stop before attempting to restart engine.
Starter System 4. Use a known, good, fully-charged battery and jumper cables to test starter motor. Be sure transmission is in neutral and PTO is OFF. Remove heavy lead from post terminal on starter. Connect one end of positive jumper cable to post terminal and connect other end to positive terminal of battery. Connect one end of negative jumper cable to negative terminal of battery. Touch other end of negative jumper cable to a bare surface on crankcase or to starter housing.
Starter System RETRACTABLE STARTERS WARNING Uncoiling Spring can cause severe injury. Wear safety goggles or face protection when servicing retractable starter. WARNING Explosive Fuel can cause fires and severe burns. Do not fill fuel tank while engine is hot or running. Retractable starters contain a powerful, recoil spring that is under tension. Always wear safety goggles when servicing retractable starters and carefully follow instructions in Retractable Starter for relieving spring tension.
Starter System 4. Remove nuts securing blower housing/retractable starter assembly to crankcase studs. 5. Remove blower housing/retractable starter assembly. Rope Replacement NOTE: Do not allow pulley/spring to unwind. Enlist aid of a helper if necessary. NOTE: Tie a double, left-hand knot in one end of new rope before starting this procedure. Rope can be replaced without complete starter disassembly. 1. Remove starter/blower housing assembly from engine. 2. Pull rope out approximately 24 in.
Disassembly/Inspection and Service WARNING Accidental Starts can cause severe injury or death. Disconnect and ground spark plug lead(s) before servicing. Before working on engine or equipment, disable engine as follows: 1) Disconnect spark plug lead(s). 2) Disconnect negative (–) battery cable from battery.
Disassembly/Inspection and Service 3. If engine has evap air cleaner base, disconnect evap hose from base. 4. Remove air cleaner base and base gasket. 5. Loosely install nuts on studs (to temporarily hold carburetor on engine). Drain Oil From Crankcase 1. Remove 1 oil drain plug and dipstick/oil fill plug. 2. Allow ample time for oil to drain from crankcase. Remove Muffler and Heat Shield Assembly 1. Remove screws and muffler assembly from exhaust outlet. 2. Remove exhaust gasket from exhaust outlet.
Disassembly/Inspection and Service Slide carburetor off mounting studs while disconnecting throttle linkage and dampening spring. Remove carburetor to insulator gasket, insulator, and insulator to cylinder head gasket. Remove Carburetor WARNING Explosive Fuel can cause fires and severe burns. Do not fill fuel tank while engine is hot or running. Remove Electric Starter (if equipped) Remove screws securing electric starter to crankcase. Remove Blower Housing/Retractable Starter 1.
Disassembly/Inspection and Service Remove Valves NOTE: Mark location of any part removed that will be reused. 1. Supporting head of valve from below, depress valve keeper and valve spring until keeper can be released from valve stem. Remove valve spring and valve from head. Repeat this procedure for remaining valve. 2. Remove and replace intake valve stem seal whenever cylinder head is serviced or disassembled.
Disassembly/Inspection and Service Hard starting, or loss of power accompanied by high fuel consumption may be symptoms of faulty valves. Although these symptoms could also be attributed to worn rings, remove and check valves first. After removal, clean valve heads, faces, and stems with a power wire brush. Then, carefully inspect each valve for defects such as warped head, excessive corrosion, or worn stem end. Replace valves found to be in bad condition.
Disassembly/Inspection and Service Crankcase Components P Q O N L M K H E I R D F G J C A B A Closure Plate Oil Seal B Closure Plate C Camshaft D E End Cap F Connecting Rod G Piston Pin Retainer H Piston I Piston Pin J Piston Ring Set K Tappet L Governor Cup M Governor Washer N Governor Shaft O Governor Gear P Governor Cross Shaft Q Crankcase Oil Seal R Dowel Pin Remove Closure Plate 1. Remove screws securing closure plate to crankcase. 2.
Disassembly/Inspection and Service 6. Engines with ACR can be started with spark plugs that are worn or fouled. Engines without ACR are more difficult to start with those same spark plugs. Automatic Compression Release (ACR) ACR Operation Details C B A E D A Camshaft B Exhaust Cam Lobe C Decompression Weight D Return Spring E Arm These engines are equipped with an ACR mechanism. ACR lowers compression at cranking speeds to make starting easier.
Disassembly/Inspection and Service Replacement ring sets are also available separately for STD pistons. Always use new piston rings when installing pistons. Never use old rings. Some important points to remember when servicing piston rings: 1. Cylinder bore must be deglazed before service ring sets are used. 2. If cylinder bore does not need reboring and if old piston is within wear limits and free of score or scuff marks, old piston may be reused. 3. Remove old rings and clean up grooves.
Disassembly/Inspection and Service 3. Top compression ring (top groove): Install top compression ring using a piston ring expander tool. Make sure identification mark is up or colored dye stripe (if contained) is left of end gap. Adjust ring gaps. Crankshaft Inspection and Service Inspect gear teeth of crankshaft and ACR gear. If any teeth are badly worn or chipped, or if some are missing, replacement of crankshaft will be necessary. Inspect crankshaft bearing surfaces for scoring, grooving, etc.
Reassembly Crankcase Components P T Q A S O N L M K H E I R D F G J C A B A Closure Plate Oil Seal B Closure Plate C Camshaft D E End Cap F Connecting Rod G Piston Pin Retainer H Piston I Piston Pin J Piston Ring Set K Tappet L Governor Cup M Governor Washer N Governor Shaft O Governor Gear P Governor Cross Shaft Q Crankcase Oil Seal R Dowel Pin S Oil Seal Depth T Outer Surface NOTE: Make sure engine is assembled using all specified torque values, tighten
Reassembly Install Governor Assembly 1. Install governor shaft through gear and add thrust washer to shaft. 2. Install governor gear assembly into crankcase using a press, or a drift with light taps, until tip of shaft is 78.862 mm (3.105 in.) below machined gasket surface of crankcase. 3. Install thrust washer and cup on governor gear shaft. 4. Install thrust washer onto governor cross shaft and slide shaft up through inside of crankcase. 5. Install second flat washer onto shaft.
Reassembly 4. Install closure plate to crankcase. Carefully seat ends of camshaft and balance shaft into their mating bearings. Rotate crankshaft slightly to help engage governor gear teeth. 5. Install screws securing closure plate to crankcase. Torque screws in sequence shown to 24 N·m (212 in. lb.).
Reassembly NOTE: Before installing flywheel make sure crankshaft taper and flywheel hub bore are clean, dry, and completely free of lubricants. Presence of lubricants can cause flywheel to be over stressed and damaged when nut is torqued to specification. NOTE: Make sure flywheel key is installed properly in keyway. Flywheel can become cracked or damaged if key is not installed properly. 1. Install woodruff key into keyway of crankshaft. Be sure that key is properly seated and parallel with taper of shaft.
Reassembly Assemble Cylinder Head NOTE: Engine utilizes a valve stem seal on intake valve. Always use a new seal when valves are installed in cylinder head. Never reuse an old seal. 1. Install valves into their respective positions. 2. Install a new valve seal on stem of intake valve. 3. Install valve springs and retainers into their respective locations in cylinder head. Using hand pressure, compress each valve spring and slide each retainer onto valve stem to lock in place. Install Cylinder Head 1.
Reassembly Blower Housing/Control Panel Components F D E C A B G H A Governor Lever B Nut C Governor Spring D Throttle Link E Dampening Spring F Control Assembly G Carburetor H Blower Housing/ Retractable Starter Assembly Install Throttle Plate Install throttle plate with screws. Install Carburetor 1. Install a new insulator to cylinder head gasket onto carburetor studs, followed by insulator, carburetor to insulator gasket, carburetor, and air cleaner gasket. 2.
Reassembly External Engine Components G J D I K E C J F H K B G I A A Oil Drain Plug B Dipstick/Oil Fill Plug C Fuel Tank D Fuel Tank Cap E Muffler Assembly F Breather Tube G Air Cleaner Base H Spit Cup Cover I Foam Element J Paper Element K Air Cleaner Cover Install Fuel Tank 1. Route fuel line across top of blower housing through clips and toward carburetor while positioning fuel tank on crankcase mounting brackets.
Reassembly Install Air Cleaner Base, Element, and Cover 1. Install air cleaner base gasket onto carburetor studs. 2. Connect breather tube to air cleaner base. If engine has evap air cleaner base, connect evap hose to base. 3. Install air cleaner base onto carburetor studs and secure with nuts. Torque nuts to 8 N·m (70.8 in. lb.). 4. Install spit cup cover on base (if equipped). 5. Install element into base. 6. Install cover and secure cover latch. Prepare Engine for Operation Engine is now reassembled.
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18 690 06 Rev. B KohlerEngines.
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