Kohler K91

Kohler K91The 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 modelK91
Engine type4-stroke, L-head, single-cylinder
Displacement145 cm3, (8.85 cu·in)
Max. horsepower4.1 PS (3.0 kW; 4.0 HP) at 4,000 rpm
Max. torque
Cooling systemForced air
Air cleanerPaper air cleaner (oiled foam precleaner)
Lubricating systemSplash type
Ignition systemMagneto ignition system, battery ignition system, breakerless ignition system
Fuel systemCarburetor (Kohler or Walbro – fixed main jet or adjustable main jet)
Fuel consumption
Fuel tank capacity
Fuel usedUnleaded gasoline (octane number 86 or higher)
Starting systemRecoil or electric starter
GovernorCentrifugal governor
PTO shaft rotationCounterclockwise (from PTO shaft side)
Dimensions (L x W X H)
Dry weight19.5 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)
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 bolt23 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 plug25-30 Nm; 2.55-3.06 kg·m; 18-22 ft·lb

Service Data

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)


1. Kohler K91, K141, K161, K181, K241, K301, K321, K341, service manual. Kohler Co. 1992.

Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

ATTENTION! Dear visitors, this is an informational database of technical specifications, we are not a parts supplier or a marketplace.

We try to use official documentation and verify the published data, but errors may occur. In addition, specifications of machinery and equipment may vary depending on markets and modifications. We do not recommend the use of this data for spare parts or repairs. Use official service manuals or parts catalogs for your product.

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