The Kohler CH621 is a 624 cc, (38.0 cu·in) V-twin air-cooled four-stroke internal combustion gasoline engine from the Command PRO series, manufactured by Kohler Co.
The Kohler CH621 engine has an OHV (overhead valve) design, an aluminum block with cast iron cylinder liners, a horizontal PTO-shaft, pressurized lubrication system. This engine is equipped with a carburetor (Nikki or Keihin) with a fixed main jet and one of these ignition systems: CDI/MDI, ASAM/DSAM, DSAI (Digital Spark Advance Ignition).
The cylinder bore and the piston stroke are 77.0 mm (3.03 in) and 67.0 mm (2.64 in), respectively. Compression ratio rating is 8.5:1.
The CH621 engine produced 19.3 PS (14.2 KW; 19.0 HP) at 3,600 rpm of horsepower and 43.6 Nm (4.45 kg·m; 32.2 ft·lb) at 2,200 rpm of torque.
The breakdown of the engine code is as follows:
- C – Command series
- H – Horizontal PTO shaft
- 621 – Numerical designation
General information
| Engine Specifications | |
| Model | Command PRO CH621 |
| Type | 4-stroke, OHV, V-twin |
| Displacement | 624 cm 3 (38.0 cu-in) |
| Max. horsepower | 19.3 PS (14.2 KW; 19.0 HP) at 3,600 rpm |
| Max. torque | 43.6 Nm (4.45 kg·m; 32.2 ft·lb) at 2,200 rpm |
| Fuel system | Carburetor with a fixed main jet (Nikki or Keihin) |
| Cooling system | Forced-air |
| Ignition system | CDI/MDI, ASAM/DSAM, DSAI (Digital Spark Advance Ignition) |
| Lubricating system | Pressurized lubrication |
| Starting system | Electric starter |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| 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 | |
| Bore x Stroke | 77.0 mm X 67.0 mm (3.03 x 2.64 in) | |
| Sleeve internal diameter | 77.000-77.025 mm (3.0315-3.0325 in) | |
| Number of piston rings (compression / oil): | 2 / 1 | |
| Thrust face outer diameter | 76.943-76.961 mm (3.0292-3.0299 in) | |
| Piston pin outer diameter | 16.995-17.000 mm (0.6691-0.6693 in) | |
| Ring-to-groove side clearance: | Top | 0.040-0.080 mm (0.0016-0.0031 in) |
| Second | 0.040-0.080 mm (0.0016-0.0031 in) | |
| 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) |
| Second | 0.250-0.450 mm (0.0098-0.0177 in) | |
| 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) | |
| Cylinder Head | ||
| Valve Arrangement: | OHV, gear drive | |
| Valves: | 4 (2 per cylinder) | |
| Valve head diameter: | INTAKE | 33.370-33.630 mm (1.3138-1.324 in) |
| EXHAUST | 29.370-29.630 mm (1.1563-1.1665 in) | |
| Stem outer diameter: | INTAKE | 6.982-7.000 mm (0.2749-0.2756 in) |
| EXHAUST | 6.970-6.988 mm (0.2744-0.2751 in) | |
Tightening torque specs
| Tightening torque specs | |
| 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) |
| Flywheel | 66.4 Nm (6.77 kg·m; 49 ft·lb) |
| Spark plug | 27 Nm (2.75 kg·m; 20.0 ft·lb) |
Service Information
| Oil system | |
| 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) |
| Ignition system | |
| Spark plug | Champion RC12YC |
| Spark plug gap | 0.76 mm (0.030 in) |
| Ignition module air gap | 0.280-0.330 mm (0.011-0.013 in) |
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