Kohler CH740

Kohler CH740The Kohler CH740 is a 725 cc (44.24 cu·in) natural aspirated V-twin four-stroke air-cooled internal combustion small gasoline engine from the Command PRO series with a horizontal shaft, manufactured by Kohler Co for general-purpose applications.

A 83.0 mm (3.27 in) cylinder bore and 67.0 mm (2.64 in) piston stroke give the CH740 engine a total of 725 cc of displacement. The compression ratio rating is 9.0:1.

The CH740 engine produced 25.3 PS (18.6 kW; 25.0 HP) at 3,600 rpm of maximum horsepower and 53.1 N·m (5.4 kg·m, 39.1 ft·lb) at 3,000 rpm of maximum torque or 27.3 PS (20.1 kW; 27.0 HP) at 3,600 rpm of maximum horsepower and 57.3 N·m (5.8 kg·m; 42.3 ft·lb) at 3,000 rpm of peak torque, depending on engine version.

The Kohler CH740 features:

  • OHV design
  • Hydraulic valve lifters
  • Aluminum cylinder block
  • Cast iron cylinder liners
  • Hardened crank journals
  • PTO side-load sleeve bearing
  • CDI/MDI, ASAM/DSAM, DSAI (Digital Spark Advance Ignition) ignition system
  • Carburetor with fixed main jet (Nikki or Keihin)
  • Mechanical centrifugal governor
  • Full pressure lubrication system
  • Forced air cooling system
  • Electric starter

General information

Engine Specifications
Engine model Command PRO CH740
Engine type 4-stroke, OHV, V-twin
Displacement 725 cm3, (44.24 cu·in)
Max. horsepower 25.3 PS (18.6 kW; 25.0 HP) at 3,600 rpm
27.3 PS (20.1 kW; 27.0 HP) at 3,600 rpm
Max. torque 53.1 N·m (5.4 kg·m, 39.1 ft·lb) at 3,000 rpm
57.3 N·m (5.8 kg·m; 42.3 ft·lb) at 3,000 rpm
Cooling system Forced air
Air cleaner Replaceable, paper element
Lubricating system Full pressure
Ignition system CDI/MDI, ASAM/DSAM, DSAI (Digital Spark Advance Ignition)
Fuel system Carburetor with fixed main jet (Nikki or Keihin)
Fuel used Unleaded gasoline (octane number 86 or higher)
Starting system Electric starter
Governor Mechanical centrifugal governor
PTO shaft rotation Counterclockwise (from PTO shaft side)
Dimensions (L x W X H) 355 x 451 x 483 mm (14.0 x 17.7 x 19.0 in)
Dry weight 43.0 kg (94.0 lbs)

Cylinder Block and Head

Cylinder block
Compression ratio: 9.0:1
Cylinder bore: 83.0 mm (3.27 in)
Piston stroke: 67.0 mm (2.64 in)
Cylinder internal diameter (standard): 82.988-83.013 mm (3.2672-3.2682 in)
Number of piston rings (compression / oil): 2/1
Piston pin diameter: 16.995-17.000 mm (0.6691-0.6693 in)
Piston style A
Thrust face outer diameter (standard): 82.949-82.967 mm (3.2656-3.2664 in)
Side clearance (Top): 0.025-0.048 mm (0.001-0.0019 in)
Side clearance (Second): 0.015-0.037 mm (0.0006-0.0015 in)
Side clearance (Oil): 0.026-0.176 mm (0.001-0.0069 in)
Ring end gap (Top): 0.25-0.560 mm (0.0098-0.022 in)
Ring end gap (Second): 0.25-0.560 mm (0.0098-0.022 in)
Piston style B
Thrust face outer diameter (standard): 82.978 mm (3.2668 in)
Side clearance (Top): 0.030-0.070 mm (0.0010-0.0026 in)
Side clearance (Second): 0.030-0.070 mm (0.0010-0.0026 in)
Side clearance (Oil): 0.060-0.190 mm (0.0022-0.0073 in)
Ring end gap (Top): 0.189-0.277 mm (0.0074-0.0109 in)
Ring end gap (Second): 1.519-1.797 mm (0.0598-0.0708 in)
Crankshaft
Number of main bearings: 2
Crankshaft main journal diameter: 40.913-40.935 mm (1.6107-1.6116 in)
Crankpin journal diameter: 35.955-35.973 mm (1.4155-1.4163 in)
Crankshaft center distance: 33.5 mm (1.32 in)
Cylinder head
Valve arrangement: OHV, gear driven
Valves: 2 (4 valves in total)
Valve head diameter (INTAKE): 33.370-33.630 mm (1.3138-1.324 in)
Valve head diameter (EXHAUST): 29.370-29.630 mm (1.1563-1.1665 in)
Valve seat angle (INTAKE): 89°
Valve seat angle (EXHAUST): 89°
Valve seat angle (INTAKE): 45°
Valve seat angle (EXHAUST): 45°
Valve steam diameter (INTAKE): 6.982-7.000 mm (0.2749-0.2756 in)
Valve steam diameter (EXHAUST): 6.970-6.988 mm (0.2744-0.2751 in)
Valve lift minimal (INTAKE): 8.07 mm (0.3177 in)
Valve lift minimal (EXHAUST): 8.07 mm (0.3177 in)
Camshaft journal diameter : 19.962-19.975 mm (0.7859-0.7864 in)

Tightening torque specs

Tightening torque specs
Intake manifold mounting (torque in 2 increments) Step 1: 7.4 Nm (0.75 kg·m; 5.5 ft·lb)
Step 2: 9.9 Nm (1.00 kg·m; 7.3 ft·lb)
Connecting rod 8 mm straight shank: 22.7 Nm (2.32 kg·m; 16.75 ft·lb)
8 mm step-down: 14.7 Nm (1.5 kg·m; 10.85 ft·lb)
6 mm straight shank: 11.3 Nm (1.15 kg·m; 8.34 ft·lb)
Carburetor mounting nut 6.2-7.3 Nm (0.63-0.74 kg·m; 4.6-5.4 ft·lb)
Cylinder head Nut (torque in 2 increments):
Step 1: 16.9 Nm (1.72 kg·m; 12.5 ft·lb)
Step 2: 35.5 Nm (3.62 kg·m; 26.2 ft·lb)
Bolt (torque in 2 increments)
Step 1: 22.6 Nm (2.31 kg·m; 16.7 ft·lb)
Step 2: 41.8 Nm (4.26 kg·m; 30.8 ft·lb)
Fan 9.9 Nm (1.0 kg·m; 7.3 ft·lb)
Flywheel 66.4 Nm (6.77 kg·m; 49.0 ft·lb)
Governor lever nut 6.8 Nm (0.69 kg·m; 5.02 ft·lb)
Muffler retaining nuts 24.4 Nm (2.5 kg·m; 18.0 ft·lb)
Spark plug 27 Nm (2.75 kg·m; 20.0 ft·lb)
Oil drain plug 13.6 Nm (1.4 kg·m; 10.0 ft·lb)

Service Data

Engine
Maximum speed: 3600±50 rpm
Idle speed: 1200±75 rpm
Compression pressure
Standard: 1.1 MPa (160 psi)
Compression differential limit between cylinders: 15% and less
Oil system
Lubrication system: Full pressure
Oil type: API SG, SH, SJ, or higher
Recommended oil: SAE 10W-30
Oil capacity: W/o oil filter: 1.7 L (1.8 US. qt, 1.5 Imp. qt.)
With oil filter: 1.9 L (2.0 US.qts, 1.7 Imp. qts)
Fuel system
Type: Carburetor with fixed main jet (Nikki or Keihin)
Fuel pump: Pulse type
Fuel filter: In-line
Main fuel: 2-1/2 turns
Idle fuel: 3/4 to 1 full turn
Ignition system
Type: CDI/MDI, ASAM/DSAM, DSAI (Digital Spark Advance Ignition)
Spark plug: Champion RC12YC
Spark plug gap: 0.76 mm (0.030 in)
Ignition coil air gap 0.280-0.330 mm (0.011-0.013 in)

References

1. Kohler Command CH18-CH25, CH620-CH730, CH740, CH750 service manual. Kohler Co. 2022.

Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

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We try to use official documentation and verify the published data, but errors may occur. In addition, specifications of machinery and equipment may vary depending on markets and modifications. We do not recommend the use of this data for spare parts or repairs. Use official service manuals or parts catalogs for your product.

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