The Kohler CH620 is a 624 cc, (38.0 cu·in) or 674 cc, (41.0 cu·in) natural aspirated V-twin four-stroke air-cooled internal combustion small gasoline engine from the Command PRO series with a vertical shaft, manufactured by Kohler Co for general-purpose applications.
It has a 77.0 mm (3.03 in) cylinder bore and 67.0 mm (2.64 in) piston stroke for the 624 cc version or an 80.0 mm (3.15 in) cylinder bore and 67.0 mm (2.64 in) piston stroke for the 674 cc version. The compression ratio rating is 8.5:1.
The CH620 engine produced 18.2 PS (13.4 KW; 18.0 HP) at 3,600 rpm or 19.3 PS (14.2 KW; 19.0 HP) at 3,600 rpm of maximum horsepower and 47.5 Nm (4.8 kg·m; 35.0 ft·lb) at 2,200 rpm of maximum torque.
The Kohler CH620 features:
- OHV design
- Hydraulic valve lifters
- Aluminum cylinder block
- Cast iron cylinder liners
- Hardened crank journals
- PTO side-load sleeve bearing
- Electronic 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 CH620 |
| Engine type | 4-stroke, OHV, V-twin |
| Displacement | 624 cm 3 (38.0 cu-in) 674 cm 3 (41.0 cu-in) |
| Max. horsepower | 18.2 PS (13.4 KW; 18.0 HP) at 3,600 rpm 19.3 PS (14.2 KW; 19.0 HP) at 3,600 rpm |
| Max. torque | 47.5 Nm (4.8 kg·m; 35.0 ft·lb) at 2,200 rpm |
| Cooling system | Forced air |
| Air cleaner | Replaceable, paper element |
| Lubricating system | Full pressure |
| Ignition system | Electronic 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 | 41.0 kg (90.0 lbs) |
Cylinder Block and Head
| Cylinder block | |
| Compression ratio: | 8.5:1 |
| Cylinder bore: | 624 cc: 77.0 mm (3.03 in) 674 cc: 80.0 mm (3.15 in) |
| Piston stroke: | 67.0 mm (2.64 in) |
| Cylinder internal diameter (standard): | 624 cc: 77.000-77.025 mm (3.0315-3.0325 in) 674 cc: 80.000-80.025 mm (3.1496-3.1506 in) |
| Number of piston rings (compression / oil): | 2/1 |
| Piston pin diameter: | 16.995-17.000 mm (0.6691-0.6693 in) |
| 624 cc | |
| Thrust face outer diameter (standard): | 76.943-76.961 mm (3.0292-3.0299 in) |
| Side clearance (Top): | 0.040-0.080 mm (0.0016-0.0031 in) |
| Side clearance (Second): | 0.040-0.080 mm (0.0016-0.0031 in) |
| Side clearance (Oil): | 0.060-0.202 mm (0.0024-0.0080 in) |
| Ring end gap (Top): | 0.250-0.450 mm (0.0098-0.0177 in) |
| Ring end gap (Second): | 0.250-0.450 mm (0.0098-0.0177 in) |
| 674 cc | |
| Piston style A | |
| Thrust face outer diameter (standard): | 79.943-79.961 mm (3.1473-3.1480 in) |
| Side clearance (Top): | 0.030-0.076 mm (0.0012-0.0030 in) |
| Side clearance (Second): | 0.030-0.076 mm (0.0012-0.0030 in) |
| Side clearance (Oil): | 0.046-0.196 mm (0.0018-0.0077 in) |
| Ring end gap (Top): | 0.180-0.460 mm (0.0071-0.0181 in) |
| Ring end gap (Second): | 0.180-0.460 mm (0.0071-0.0181 in) |
| Piston style B | |
| Thrust face outer diameter (standard): | 79.966 mm (3.1483 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): | 0.100-0.279 mm (0.0039-0.0110 in) |
| Ring end gap (Second): | 1.400-1.679 mm (0.0551-0.0661 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 |
| Ignition system | |
| Type: | Electronic ignition system |
| 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.
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