The Kohler TH18/TH18S is a 574 cc (35.0 cu·in) V-twin air-cooled four-stroke internal combustion gasoline engine from the Triad series, manufactured by Kohler Co.
The Kohler TH18 engine has an OHC (overhead camshaft) design, an aluminum block with cast iron cylinder liners, a horizontal PTO-shaft, fuul-pressurized lubrication system, replaceable high-density paper air cleaner. This engine is equipped with a carburetor with a fixed main jet, electronic ignition system (CDI).
A 75.0 mm (2.95 in) cylinder bore and 65.0 mm (2.56 in) piston stroke give the TH18 engine a total of 574 cc of displacement. The compression ratio rating is 8.4:1.
This engine produced 18.2 PS (13.4 KW; 18.0 HP) at 3,600 rpm of horsepower and 40.0 Nm (4.1 kg·m; 29.5 ft·lb) at 2,500 rpm of torque.
The breakdown of the engine code is as follows:
- T – Triad series
- H – Horizontal PTO shaft
- 18 – 18.0 HP
- Version code:
- S – Electric start
General information
| Engine Specifications | |
| Model | Triad TH18 / TH18S |
| Type | 4-stroke, OHV, V-twin |
| Displacement | 574 cm 3 (35.0 cu-in) |
| Max. horsepower | 18.2 PS (13.4 KW; 18.0 HP) at 3,600 rpm |
| Max. torque | 40.0 Nm (4.1 kg·m; 29.5 ft·lb) at 2,500 rpm |
| Fuel system | Carburetor with a fixed main jet |
| Cooling system | Forced-air |
| Ignition system | Electronic ignition (CDI) |
| Lubricating system | Full-pressure lubrication |
| Starting system | Recoil or electic starter |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Dimensions (L x W X H) | 328 x 400 x 449 mm (12.9 x 15.7 x 17.7 in) |
| Dry weight | 43.0 kg (90.0 lbs) |
Cylinder Block and Head
| Cylinder block | ||
| Compression ratio: | 8.4:1 | |
| Bore x Stroke | 75.0 mm X 65.0 mm (2.95 x 2.56 in) | |
| Sleeve internal diameter | 75.025-75.050 mm (2.9537-2.9547 in) | |
| Number of piston rings (compression / oil): | 2 / 1 | |
| Thrust face outer diameter | 74.966-74.984 mm (2.9514-2.9521 in) | |
| Piston pin outer diameter | 16.996-17.000 mm (0.6691-0.6693 in) | |
| Ring-to-groove side clearance: | Top | 0.040-0.085 mm (0.0016-0.0033 in) |
| Second | 0.030-0.076 mm (0.0012-0.0030 in) | |
| Oil (min) | 0.070 mm (0.0028 in) | |
| Ring end gap: | Top | 0.180-0.380 mm (0.0071-0.0150 in) |
| Second | 0.180-0.450 mm (0.0071-0.0177 in) | |
| Crankshaft main journal diameter: | 45.021-45.041 mm (1.7725-1.7735 in) | |
| Crankpin journal diameter: | 31.948-31.966 mm (1.5338-1.2193 in) | |
| Cylinder Head | ||
| Valve Arrangement: | OHC, belt driven | |
| Valves: | 2 (4 in total) | |
| Valve head diameter: | INTAKE | 29.180-29.430 mm (1.1488-1.1586 in) |
| EXHAUST | 26.300-26.700 mm (1.0354-1.0512 in) | |
| Stem outer diameter: | INTAKE | 5.982-6.000 mm (0.2355-0.2362 in) |
| EXHAUST | 5.970-5.988 mm (0.2350-0.2357 in) | |
Tightening torque specs
| Tightening torque specs | |
| Connecting rod | 11.3 Nm (1.2 kgf·m; 8.3 ft·lb) |
| Oil drain plug | 16.3 Nm (1.7 kgf·m; 12.0 ft·lb) |
| Oil filter | 5.6-9.0 Nm (0.6-0.9 kgf·m; 4.1-6.6 ft·lb) |
| Muffler retaining nuts | 24.4 Nm (2.5 kgf·m; 18 ft·lb) |
| Valve cover | 5.6 Nm (0.6 kgf·m; 4.1 ft·lb) |
| Flywheel | 66.4 Nm (6.77 kg·m; 49 ft·lb) |
| Spark plug | 24.4-29.8 Nm (2.5-3 kgf·m; 18-22 ft·lb) |
Service Information
| Valve clearance | |
| Intake | 0.013-0.064 mm (0.0005-0.0025 in) |
| Exhaust | 0.076-0.127 mm (0.0030-0.0050 in) |
| Oil system | |
| Oil type | API SG, SH, SJ, or higher |
| Recommended oil | SAE 10W-30 |
| Oil capacity | 1.4 liters (1.48 US.qts, 1.23 Imp. qts) |
| Ignition system | |
| Spark plug | Champion RC12YC |
| Spark plug gap | 0.76 mm (0.030 in) |
| Ignition module air gap | 0.200-0.300 mm (0.0079-0.0118 in) |
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