_______________________________________________________________________________________

Kohler Command CH740S

General Technical Data

Kohler CH740S Engine Specifications

Engine Model ..................... Kohler Command CH740S
Engine Type ..................... Gasoline, 4-cycle V-Twin air-cooled
Number of Cylinders ..................... 2
Displacement, cc (cu.in) ..................... 725 (44.0)
Engine Bore, mm (in) ..................... 83.0 (3.27)
Engine Stroke, mm (in) ..................... 67.0 (2.64)
Rated Engine Power, hp (kW) ..................... 25.0 (18.6)
Rated Engine Speed, rpm ..................... 3600
Maximum Torque, Nm (ft-lbs) ..................... 53.1 (39.2)
Torque Speed, rpm ..................... 2800
Compression ..................... 9.0:1
Lubrication ..................... Full pressure
Oil filter ..................... Full-flow type
Air Cleaner ..................... Replaceable, paper element
Oil Capacity, L (qts) ..................... 1.9 (2.0)
Electrical System Rating, Volts ..................... 12
Starter Type ..................... Electric

Fuel System

Fuel System Type ..................... Carburetor
Carburetor Model ..................... Keihin
Carburetor Type ..................... One-Barrel, fixed main jet
Fuel Pump Type ..................... Pulse/mechanical
Fuel Filter ..................... In-line
Governor ..................... Mechanical

Dimensions

Length, mm (in) ..................... 355 (14.0)
Width, mm (in) ..................... 450 (17.7)
Height, mm (in) ..................... 483 (19.0)
Net weight, kg (lbs) ..................... 41.0 (90)

Kohler CH740S Maintenance Data

Cylinder Block and Valves

Cylinder Bore I.D. (Maximum), mm (in) ..................... 83.051 (3.2697)
Cylinder Head (Max. Out-of-Flatness), mm (in) ..................... 0.076 (0.003)
Intake Valve Clearance (Cold), mm (in) ..................... 0.038-0.076 (0.0015-0.0030)
Exhaust Valve Clearance (Cold), mm (in) ..................... 0.050-0.088 (0.0020-0.0035)

Engine Oil

Engine Oil Type (Summer Time) ..................... SAE 10W-30
Engine Oil Type (Winter Time) ..................... SAE 5W-30
Oil Classification ..................... API SJ or higher
Oil Capacity (w/o Filter), L (qts) ..................... 1.6 (1.7)
Oil Capacity (with New Filter), L (qts) ..................... 1.8 (1.9)

Carburetor Adjustment

Main Fuel ..................... 2-1/2 turns
Idle Fuel ..................... 3/4 to 1 full turn
Low Idle Speed, rpm ..................... 1200±75
High Idle Speed, rpm ..................... 3600±50

Ignition System

Spark Plug Type ..................... Champion RC12YC
Spark Plug Gap, mm (in) ..................... 0.76 (0.030)
Module Air Gap, mm (in) ..................... 0.28-0.33 (0.011-0.013)
Thread Size, mm (in) ..................... 14 (0.55)
Reach, mm (in) ..................... 19.1 (0.75)
Spark Plug Torque, Nm (ft-lbs) ..................... 27 (20)

Service Intervals

Service Or Replace Low-Profile Precleaner ..................... Every 25 hours
Replace Air Cleaner Element ..................... Every 100 hours
Change Engine Oil ..................... Every 100 hours
Clean Oil Cooler Fins ..................... Every 100 hours
Change Oil Filter ..................... Every 200 hours
Replace Fuel Filter ..................... Every 200 hours
Check Carburetor Adjustment ..................... Every 200 hours
Check and Adjust Valve Clearance ..................... Every 500 hours
Check Spark Plug Condition and Gap ..................... Every 500 hours
Replace Spark Plug ..................... Every 500 hours

Kohler CH740S Service Specifications

Cylinder Block

Cylinder Bore I.D (Standard) ..................... 82.988-83.013 mm (3.2672-3.2682 in)
Cylinder Bore I.D (Max. Wear Limit) ..................... 83.051 mm (3.2697 in)
Cylinder Bore (Max. Out of Round) ..................... 0.12 mm (0.0047 in)
Cylinder Bore Max. Taper ..................... 0.05 mm (0.0020 in)
Cylinder Head Max. Out of Flatness ..................... 0.076 mm (0.003 in)
Camshaft End Play (W/Shim) ..................... 0.076-0.127 mm (0.0030-0.0050 in)
Camshaft Clearance ..................... 0.025-0.063 mm (0.0010-0.0025 in)
Camshaft Bore I.D ..................... 20.000-20.025 mm (0.7874-0.7884 in)
Camshaft Bearing Surface O.D ..................... 19.962-19.975 mm (0.7859-0.7864 in)
Connecting Rod to Crankpin Clearance ..................... 0.030-0.055 mm (0.0012-0.0022 in)
Connecting Rod to Crankpin Side Clearance ..................... 0.26-0.63 mm (0.0102-0.0248 in)
Connecting Rod to Piston Pin Clearance ..................... 0.015-0.028 mm (0.0006-0.0011 in)

Valves

Hydraulic Valve Lifter to Crankcase Clearance ..................... 0.0241-0.0501 mm (0.0009-0.0020 in)
Intake Valve Stem to Valve Guide Clearance ..................... 0.038-0.076 mm (0.0015-0.0030 in)
Exhaust Valve Stem to Valve Guide Clearance ..................... 0.050-0.088 mm (0.0020-0.0035 in)
Intake Valve Guide I.D ..................... 7.038-7.058 mm (0.2771-0.2779 in)
Exhaust Valve Guide I.D ..................... 7.038-7.058 mm (0.2771-0.2779 in)
Valve Guide Reamer Size (Standard) ..................... 7.048 mm (0.2775 in)
Valve Guide Reamer Size (0.25 Oversize) ..................... 7.298 mm (0.2873 in)
Intake Valve Minimum Lift ..................... 8.07 mm (0.3177 in)
Exhaust Valve Minimum Lift ..................... 8.07 mm (0.3177 in)
Nominal Valve Face Angle ..................... 45 degrees
Valve Seat Angle (Intake/Exhaust) ..................... 89 degrees
Intake Valve Insert O.D ..................... 36.987-37.013 mm (1.4562-1.4572 in)
Exhaust Valve Insert O.D ..................... 32.987-33.013 mm (1.2987-1.2997 in)
Intake Valve Guide Depth ..................... 4.00 mm (0.1575 in)
Exhaust Valve Guide Depth ..................... 6.50 mm (0.2559 in)
Intake Valve Head Diameter ..................... 33.37-33.63 mm (1.3138-1.3240 in)
Exhaust Valve Head Diameter ..................... 29.37-29.63 mm (1.1563-1.1665 in)
Intake Valve Stem Diameter ..................... 6.982-7.000 mm (0.2749-0.2756 in)
Exhaust Valve Stem Diameter ..................... 6.970-6.988 mm (0.2744-0.2751 in)

Crankshaft

Crankshaft End Play (Free) ..................... 0.070-0.590 mm (0.0028-0.0230 in)
Crankshaft Bore (In Crankcase) ..................... 40.965-41.003 mm (1.6128-1.6143 in)
Crankshaft Bore (In Closure Plate) ..................... 40.987-40.974 mm (1.6136-1.6131 in)
Crankshaft Bore to Crankshaft Clearance ..................... 0.039-0.074 mm (0.0015-0.0029 in)
Flywheel End Main Bearing Journal O.D ..................... 40.913-40.935 mm (1.6107-1.6116 in)
Flywheel End Main Bearing Journal Max. Taper ..................... 0.022 mm (0.0009 in)
Closure Plate End Main Bearing Journal O.D ..................... 40.913-40.935 mm (1.6107-1.6116 in)
Closure Plate End Main Bearing Journal Max. Taper ..................... 0.022 mm (0.0009 in)
Connecting Rod Journal O.D ..................... 35.955-35.973 mm (1.4156-1.4163 in)
Connecting Rod Journal Max. Taper ..................... 0.018 mm (0.0007 in)
Crankshaft T.I.R (PTO End, Crank in Engine) ..................... 0.279 mm (0.0110 in)
Crankshaft T.I.R (Entire Crank, in V-Blocks) ..................... 0.10 mm (0.0039 in)

Piston and Piston Rings

Piston to Piston Pin Clearance ..................... 0.006-0.017 mm (0.0002-0.0007 in)
Piston Pin Bore I.D ..................... 17.006-17.012 mm (0.6695-0.6698 in)
Piston Pin O.D ..................... 16.995-17.000 mm (0.6691-0.6693 in)
Top Compression Ring Groove Clearance ..................... 0.025-0.048 mm (0.0010-0.0019 in)
Middle Compression Ring Groove Clearance ..................... 0.015-0.037 mm (0.0006-0.0015 in)
Oil Control Ring Groove Clearance ..................... 0.026-0.176 mm (0.0010-0.0070 in)
Top and Middle Compression Ring End Gap ..................... 0.25-0.56 mm (0.0100-0.0224 in)
Piston Thrust Face O.D (Std) ..................... 82.986 mm (3.2671 in)
Piston Thrust Face O.D (Wear Limit) ..................... 82.841 mm (3.2614 in)
Piston Thrust Face to Cylinder Bore Clearance ..................... 0.001-0.045 mm (0.039-0.0018 in)

Kohler CH740S Tightening Torque Specs

Cylinder Head Nut, Nm (ft-lb) ..................... 16.9-33.9 (12.5-25.1)
Cylinder Head Bolt, Nm (ft-lb) ..................... 22.6-41.8 (16.7-30.8)
Rocker Arm Screw, Nm (ft-lb) ..................... 11.3 (8.3)
Connecting Rod Cap, Nm (ft-lb) ..................... 11.3 (8.3)
Flywheel Retaining Screw, Nm (ft-lb) ..................... 66.4 (49.1)
Intake Manifold Mounting, Nm (ft-lb) ..................... 7.4 (5.5)
Carburetor Mounting Nut, Nm (ft-lb) ..................... 6.2-7.3 (4.6-5.4)
Closure Plate, Nm (ft-lb) ..................... 24.4 (18.1)
Oil Drain Plug, Nm (ft-lb) ..................... 13.6 (10.1)
Governor Lever Nut, Nm (ft-lb) ..................... 6.8 (5.1)
Ignition Module, Nm (ft-lb) ..................... 4.0-6.2 (2.9-4.6)
Muffler Retaining Nut, Nm (ft-lb) ..................... 24.4 (18.1)
Fuel Pump Screw, Nm (ft-lb) ..................... 2.3 (1.7)
Spark Plug, Nm (ft-lb) ..................... 27 (20.1)