The Kohler K91 is a 145 cc, (8.85 cu·in) natural aspirated single-cylinder four-stroke air-cooled internal combustion small gasoline engine with a horizontal shaft, manufactured by Kohler Co for general-purpose applications.
It has a 60.33 mm (2.38 in) cylinder bore and 50.80 mm (2.00 in) piston stroke. The K91 engine produced 4.1 PS (3.0 kW; 4.0 HP) at 4,000 rpm of maximum horsepower.
The Kohler K91 features:
- L-head (side valve) design
- Magneto ignition system, battery ignition system or breakerless ignition system ignition system*
- Carburetor (Kohler or Walbro – fixed main jet or adjustable main jet)*
- Centrifugal governor
- Splash type lubrication system
- Forced air cooling system
- Recoil or electric starter
*-depending on modification
General information
| Engine Specifications | |
| Engine model | K91 |
| Engine type | 4-stroke, L-head, single-cylinder |
| Displacement | 145 cm3, (8.85 cu·in) |
| Max. horsepower | 4.1 PS (3.0 kW; 4.0 HP) at 4,000 rpm |
| Max. torque | – |
| Cooling system | Forced air |
| Air cleaner | Paper air cleaner (oiled foam precleaner) |
| Lubricating system | Splash type |
| Ignition system | Magneto ignition system, battery ignition system, breakerless ignition system |
| Fuel system | Carburetor (Kohler or Walbro – fixed main jet or adjustable main jet) |
| Fuel consumption | – |
| Fuel tank capacity | – |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Starting system | Recoil or electric starter |
| Governor | Centrifugal governor |
| PTO shaft rotation | Counterclockwise (from PTO shaft side) |
| Dimensions (L x W X H) | – |
| Dry weight | 19.5 kg (43 lbs) |
Cylinder Block and Head
| Cylinder block | |
| Compression ratio: | – |
| Cylinder bore: | 60.33 mm (2.38 in) |
| Piston stroke: | 50.80 mm (2.00 in) |
| Cylinder internal diameter (standard): | 60.312-60.337 mm (2.3745-2.3755 in) |
| Piston skirt outer diameter (standard): | 60.172-60.223 mm (2.369-2.371 in) |
| Number of piston rings (compression / oil): | 2/1 |
| Connecting rod small end diameter (standard): | 14.300 mm (0.563 in) |
| Piston pin diameter: | 14.282-14.287 mm (0.5623-0.5625 in) |
| Ring end gap (Top): | 0.177-0.432 mm (0.007-0.017 in) |
| Ring end gap (Second): | 0.177-0.432 mm (0.007-0.017 in) |
| Crankshaft center distance: | 25.4 mm (1 in) |
| Cylinder head | |
| Valve arrangement: | L-head (side valve) |
| Valves: | 2 |
| Valve head diameter (INTAKE): | 24.866-25.120 mm (0.979-0.989 in) |
| Valve head diameter (EXHAUST): | 20.498-20.752 mm (0.807-0.817 in) |
| Valve steam diameter (INTAKE): | 6.299-6.312 mm (0.248-0.2485 in) |
| Valve steam diameter (EXHAUST): | 6.248-6.261 mm (0.246-0.2465 in) |
Tightening torque specs
| Tightening torque specs | |
| Cylinder head bolt | 23 Nm; 2.3 kg·m; 17 ft·lb |
| Flywheel | Nut: 55-68 Nm; 5.5-6.9 kg·m; 40-50 ft·lb Screw: 28 Nm; 2.9 kg·m; 21 ft·lb |
| Spark plug | 25-30 Nm; 2.55-3.06 kg·m; 18-22 ft·lb |
Service Data
| Engine | |
| Maximum speed: | 4,000 rpm |
| Valve clearance | |
| Intake valve clearance: | 0.13-0.23 mm (0.0051-0.0091 in) |
| Exhaust valve clearance: | 0.28-0.38 mm (0.011-0.015 in) |
| Oil system | |
| Lubrication system: | Splash type |
| Oil type: | API: SF or SG |
| Recommended oil: | Summer: SAE 30W Winter: SAE 5W-20, 5W-30 |
| Oil capacity: | 0.7 L (0.74 US. qt, 0.62 Imp. qt.) |
| Fuel system | |
| Type: | Carburetor (Kohler or Walbro – fixed main jet or adjustable main jet) |
| Ignition system | |
| Type: | Magneto ignition system, battery ignition system, breakerless ignition system |
| Spark plug: | Champion RJ8C |
| Spark plug gap: | 0.65 mm (0.0256 in) |
References
1. Kohler K91, K141, K161, K181, K241, K301, K321, K341, service manual. Kohler Co. 1992.
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