The Kohler LH685 is a 674 cc (41.1 cu·in) natural aspirated V-twin four-stroke liquid-cooled internal combustion small gasoline engine with a horizontal shaft from the Aegis series, manufactured by Kohler Co for general-purpose applications.
It has an 80.0 mm (3.15 in) cylinder bore and 67.0 mm (2.64 in) piston stroke. The compression ratio rating is 8.5:1.
This engine produced 25.3 PS (18.6 KW; 25.0 HP) at 3,600 rpm of maximum horsepower and 54.3 Nm (5.54 kg·m; 40.07 ft·lb) at 2,200 rpm of peak torque.
The Kohler Aegis LH685 features:
- OHV (overhead valve) design
- Hydraulic valve system
- Electronic ignition system
- One-barrel carburetor with fixed main jet (Keihin)
- Centrifugal flyweight mechanical governor
- Full pressure with Gerotor oil pump lubrication system
- Liquid-cooled cooling system with parallel-flow radiator and integrated belt-driven water pump
- Solenoid shift starter (12V)
General information
| Engine Specifications | |
| Engine model | Aegis LH685 |
| Engine type | 4-stroke, OHV, V-twin |
| Displacement | 674 cm3, (41.1 cu·in) |
| Max. horsepower | 25.3 PS (18.6 KW; 25.0 HP) at 3,600 rpm |
| Max. torque | 54.3 Nm (5.54 kg·m; 40.07 ft·lb) at 2,200 rpm |
| Cooling system | Liquid-cooled |
| Air cleaner | Heavy-Duty air cleaner |
| Lubricating system | Full pressure with gerotor oil pump |
| Ignition system | Electronic ignition system |
| Fuel system | Carburetor with fixed main jet (Keihin) |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Starting system | Solenoid shift starter (12V) |
| Charging system | 20A charging, regulated |
| Governor | Centrifugal flyweight mechanical governor |
| PTO shaft rotation | Counterclockwise (from PTO shaft side) |
| Dimensions (L x W X H) | 432 x 459 x 674 mm (17.0 x 18.1 x 26.5 in) |
| Dry weight | 51.7 kg (114.0 lbs) |
Cylinder Block and Head
| Cylinder block | |
| Compression ratio: | 8.5:1 |
| Cylinder bore: | 80.0 mm (3.15 in) |
| Piston stroke: | 67.0 mm (2.64 in) |
| Cylinder internal diameter (standard): | 80.000-80.025 mm (3.1496-3.1506 in) |
| Number of piston rings (compression / oil): | 2/1 |
| Piston type A | |
| Piston skirt outer diameter (standard): | 79.963-79.981 mm (3.1481-3.1488 in) |
| Connecting rod small end diameter (standard): | 17.006-17.013 mm (0.6695-0.6698 in) |
| Piston pin diameter: | 16.995-17.000 mm (0.6691-0.6693 in) |
| Side clearance (Top): | 0.050-0.096 mm (0.0020-0.0038 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): | 0.180-0.430 mm (0.0071-0.0169 in) |
| Ring end gap (Second): | 0.250-0.460 mm (0.0098-0.0181 in) |
| Piston type B | |
| Piston skirt outer diameter (standard): | 79.966 mm (3.1483 in) |
| Connecting rod small end diameter (standard): | 17.006-17.013 mm (0.6695-0.6698 in) |
| Piston pin diameter: | 16.995-17.000 mm (0.6691-0.6693 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 | |
| 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 face angle (INTAKE): | 45° |
| Valve face angle (EXHAUST): | 45° |
| Seat angle (INTAKE): | 89° |
| Seat angle (EXHAUST): | 89° |
| 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 (min) (INTAKE): | 8.88 mm (0.3496 in) |
| Valve lift (min) (EXHAUST): | 8.88 mm (0.3496 in) |
| Camshaft journal diameter : | 19.962-19.975 mm (0.7859-0.7864 in) |
Tightening torque specs
| Tightening torque specs | |
| Intake manifold (torque in 2 increments) | Step 1: 7.4 Nm (0.8 kgf·m; 5.5 lb·ft) Step 2: 9.9 Nm (1.0 kgf·m; 7.3 lb·ft) |
| Carburetor mounting | 9.9 Nm (1.0 kgf·m; 7.3 lb·ft) |
| Connecting rod cap | 11.3 Nm (1.15 kg·m; 8.3 ft·lb) |
| Oil drain plugs | 13.6 Nm (1.4 kg·m; 10.0 ft·lb) |
| Cylinder head (torque in 2 increments) | Step 1: 16.9 Nm (1.7 kg·m; 12.5 ft·lb) Step 2: 33.9 Nm (3.5 kg·m; 25.0 ft·lb) |
| Rocker pivot | 11.3 Nm (1.1 kg·m; 8.34 ft·lb) |
| Rear fan shaft to mounting bracket nut | 15.8 Nm (1.6 kgf·m; 11.7 lb·ft) |
| Front fan assembly to fan shaft nut | 15.8 Nm (1.6 kgf·m; 11.7 lb·ft) |
| Flywheel | 66.4 Nm (6.77 kg·m; 49 ft·lb) |
| Spark plug | 27 Nm (2.75 kg·m; 19.93 ft·lb) |
| Muffler retaining nuts | 24.4 Nm (2.5 kg·m; 18.0 ft·lb) |
| Valve cover | 6.2 Nm (0.63 kg·m; 4.6 ft·lb) |
| Governor lever nut | 6.8 Nm (0.7 kgf·m; 5.0 lb·ft) |
Service Data
| Engine | |
| Idle speed: | 1200±75 rpm |
| Compression pressure | |
| Compression differential limit between cylinders: | 15% and less |
| Oil system | |
| Lubrication system: | Full pressure with gerotor oil pump |
| Oil type: | SAE 10W-30 |
| Recommended oil: | API SG, SH, SJ, or higher |
| Oil capacity: | W/o oil filter: 1.6 liters (1.7 US.qts, 1.4 Imp. qts) With oil filter: 1.8 liters (1.9 US.qts, 1.58 Imp. qts) |
| Ignition system | |
| Type: | Electronic ignition system |
| Spark plug: | Champion RC14YC or Kohler 6613201-S |
| Spark plug gap: | 0.76 mm (0.030 in) |
| Spark plug torque: | 27 N·m (2.8 kg·m, 19.9 ft·lb) |
| Ignition module air gap: | 0.20-0.30 mm (0.008-0.012 in) |
| Cooling system | |
| Cooling system: | Liquid-cooled cooling system with parallel-flow radiator and integrated belt-driven water pump |
| Coolant capacity: | 2.0 liters (2.1 US.qts, 1.8 Imp. qts) |
References
1. Kohler Aegis LH630, LH640, LH685, LH690, LH750, LH755 service manual. Kohler Co. 2021.
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