The Kohler Command PRO Hydro 12.75 is a 357 cc (21.8 cu·in) single-cylinder air-cooled four-stroke internal combustion gasoline engine from Command PRO series, manufactured by Kohler Co., for general-purpose applications, such as construction and industrial equipment, portable generators, commercial or residential lawn, and garden equipment.
The Kohler Hydro 12.75 engine has an OHV (overhead valve) design, cast iron cylinder liners, aluminum block, steel-forged horizontal shaft, and dual main ball bearings. This engine is equipped with fixed jet Mikuni carburetor, electronic TCI (Transistor Controlled Ignition) system, mechanical governor and automatic compression release. The Command PRO Hydro 12.75 engine can be equipped with one of three air cleaner configurations: the standard dual-element air cleaner, heavy-duty cyclonic air cleaner (option), or an oiled, solid foam element (option).
Cylinder bore and piston stroke are 85.0 mm (3.35 in) and 63.0 mm (2.48 in), respectively. Compression ratio rating is 8.1:1. The Command PRO Hydro 12.75 engine produced 12.9 PS (9.5 kW; 12.7 HP) at 3,600 rpm of horsepower and 30.6 N·m (3.1 kg·m, 22.6 ft·lb) at 2,400 rpm of torque.
The breakdown of the engine code is as follows:
- C – Command series
- S – Slanted cylinder
- 12.75 – output power 12.75 HP
- Suffix (engine is available with the following options):
S – Electric starter;
T – Retractable starter;
G – Tapered crankshaft;
P – Threaded crankshaft;
R – Gear Reduction (2:1 or 6:1);
General information
| Engine Specifications | |
| Model | Command PRO Hydro 12.75 |
| Type | 4-stroke, OHV, single cylinder |
| Displacement | 357 cm 3 (21.8 cu-in) |
| Max. horsepower | 12.9 PS (9.5 kW; 12.7 HP) at 3,600 rpm |
| Max. torque (crank PTO) | 30.6 N·m (3.1 kg·m, 22.6 ft·lb) at 2,400 rpm |
| Fuel system | Carburetor wit fixed jet (Mikuni) |
| Cooling system | Forced-air |
| Ignition system | TCI (Transistor Controlled Ignition) |
| Lubricating system | Splash type |
| Starting system | Recoil or electric starter |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Fuel tank capacity | 6.9 L (1.82 US. gal. 1.52 Imp. gal.) |
Cylinder Block and Head
The Kohler Command PRO Hydro 12.75 has aluminum cylinder block with cast iron cylinder liner, dual ball bearing supported forged steel crankshaft. The piston has two compression rings and one oil ring. An 85.0 mm (3.35 in) cylinder bore and 63.0 mm (2.48 in) piston stroke give the Command PRO Hydro 12.75 engine a total of 357 cc (20.8 cu·in) of displacement. Compression ratio rating is 8.1:1.
| Cylinder block | ||
| Compression ratio: | 8.1:1 | |
| Bore x Stroke | 85.0 X 63.0 mm (3.35 x 2.48 in) | |
| Sleeve internal diameter | 85.000-85.020 mm (3.3465-3.3472 in) | |
| Piston skirt outer diameter | 84.954-84.998 mm (3.3446-3.3464 in) | |
| Number of piston rings (compression / oil): | 2 / 1 | |
| Ring side clearance | Top | 0.040-0.080 mm (0.0016-0.0031 in) |
| Second | 0.030-0.070 mm (0.0012-0.0028 in) | |
| Ring end gap | Top | 0.250-0.400 mm (0.0098-0.0157 in) |
| Second | 0.250-0.400 mm (0.0098-0.0157 in) | |
| Oil (side rail) | 0.200-0.700 mm (0.0079-0.0276 in) | |
| Connecting rod small end ID | 20.006-20.020 mm (0.7876-0.7882 in) | |
| Connecting rod big end ID | 36.000-36.015 mm (1.4173-1.4179 in) | |
| Piston pin outer diameter | 19.995-20.000 mm (0.7872-0.7874 in) | |
| Crankshaft main journal diameter: | 72.000 mm (2.8346 in) | |
| Crankpin diameter: | 35.969-35.984 mm (1.4161-1.4167 in) | |
| Cylinder Head | ||
| Valve Arrangement: | OHV | |
| Valves: | 2 | |
| Valve head diameter: | INTAKE | 32.000 mm (1.2598 in) |
| EXHAUST | 27.000 mm (1.063 in) | |
| Stem outer diameter (standard): | INTAKE | 6.000-6.012 mm (0.2362-0.2367 in)) |
| EXHAUST | 6.000-6.012 mm (0.2362-0.2367 in) | |
| Valve length (standard): | INTAKE | 88.100 mm (3.4685 in) |
| EXHAUST | 87.900 mm (3.4606 in) | |
| Camshaft journal diameter: | 15.965-15.990 mm (0.6285-0.6295 in) | |
| Cam height: | INTAKE | 32.500-32.600 mm (1.2795-1.2835 in) |
| EXHAUST | 32.500-32.600 mm (1.2795-1.2835 in) | |
Tightening torque specs
| Tightening torque specs | |
| Cylinder head bolt | 50 Nm; 5.1 kg·m; 37 ft·lb |
| Flywheel | 120 Nm; 12.2 kg·m; 88 ft·lb |
| Oil drain plug | 20 Nm; 2.0 kg·m; 14.8 ft·lb |
| Spark plug | 20 N·m (2 kg·m, 14.7 ft·lb) |
Service Information
| Engine | |
| Idle speed | 2,000 ± 150 rpm |
| Cylinder compression | 4.0-6.0 kg/cm2 (400-600 kPa, 57-85 psi) at 600 rpm |
| Valve clearance | |
| Intake valve clearance | 0.10 mm (0.0039 in) |
| Exhaust valve clearance | 0.10 mm (0.0039 in) |
| Oil system | |
| Oil type | API SG, SH, SJ or higher |
| Recommended oil | SAE 10W-30 |
| Oil capacity | 1.1 L (1.16 US. qt, 0.97 Imp. qt.) |
| Ignition system | |
| Spark plug | NGK: BPR4ES, Champion: RN14YC, RC14YC |
| Spark plug gap | 0.8 mm (0.0315 in) |
| Ignition module air gap | 0.4-0.6 mm (0.015-0.023 in) |
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