Kohler M20

Kohler M20The Kohler M20 is a 770 cc (46.98 cu·in) two-cylinder air-cooled four-stroke internal combustion gasoline engine from the Magnum-series, manufactured by Kohler Co.

The Kohler Magnum 20 engine has an L-head (side valve) design and a horizontal PTO shaft. This engine is equipped with the Kohler or two types of Walbro-build carburetor (with fixed main jet or with adjustable mian or high speed needle) and an electronic magneto ignition system. The M20 engine used a high-density paper air cleaner.

The cylinder bore is 79.25 mm (3.12 in) and the piston stroke is 77.7 mm (3.06 in). The compression ratio rating is 6.6:1.

This engine produced 20.3 PS (14.9 KW; 20.0 HP) at 3,600 rpm of horsepower.

The breakdown of the engine code is as follows:

  • M – M-series
  • 20 – 20.0 HP horsepower
  • Suffix (engine is available with the following options):
    S – Electric starter;
    G – Tapered crankshaft (Generator applications);
    P – Threaded crankshaft (Pump applications);
    EP – Generator;
    Q – Quilet model;

General information

Engine Specifications
ModelMagnum M20
Type4-stroke, L-head, two-cylinder
Displacement770 cm 3 (46.98 cu-in)
Max. horsepower20.3 PS (14.9 KW; 20.0 HP) at 3,600 rpm
Max. torque (crank PTO)
Fuel systemKohler or Walbro carburetor
Cooling systemForced-air
Ignition systemElectronic magneto ignition system
Lubricating systemFull-pressure
Starting systemElectric starter
Fuel usedUnleaded gasoline (octane number 86 or higher)
Weight59.0 kg (130 lbs)

Cylinder Block and Head

Cylinder block
Compression ratio:6.6:1
Bore x Stroke79.25 mm X 77.7 mm (3.12 x 3.06 in)
Sleeve internal diameter79.362-79.388 mm (3.1245-3.1255 in)
Piston skirt outer diameter79.268-79.286 mm (3.1208-3.1215 in)
Number of piston rings (compression / oil):2 / 1
Ring end gapTop0.253-0.582 mm (0.010-0.023 in)
Second0.253-0.582 mm (0.010-0.023 in)
Piston pin outer diameter19.047-19.052 mm (0.7499-0.7501 in)
Main bearing surface (max)44.213 mm (1.7407 in)
Crankpin outer diemeter38.082-38.095 mm (1.4993-1.4998 in)
Cylinder Head
Valve Arrangement:L-head (sidevalve)
Valve minimum lift – Zero lash:INTAKE6.9 mm (0.274 in)
EXHAUST6.9 mm (0.274 in)
Stem outer diameter (standard):INTAKE7.881 mm (0.3103 in)
EXHAUST7.843 mm (0.3088 in)

Tightening torque specs

Tightening torque specs
Cylinder head bolt20-37 Nm; 2.04-3.77 kg·m; 14.8-27.3 ft·lb
Spark plug18 N·m; 1.8 kg·m; 13.3 ft·lb

Service Information

Max speed3,600 rpm
Valve clearance
Intake valve clearance0.076-0.152 mm (0.003-0.006 in)
Exhaust valve clearance S/n 1816500646 and earlier: 0.406-0.482 mm (0.016-0.019 in)
S/n 1816500656 and later: 0.278-0.354 mm (0.011-0.014 in)
Oil system
Oil typeAPI SF or SG
Recommended oil Summer: SAE 30W
Winter: SAE 5W-20, 5W-30
Oil capacity (with filter) With oil filter: 1.6 L (1.69 US. qt, 1.41 Imp. qt.)
W/o oil filter: 1.4 L (1.48 US. qt, 1.23 Imp. qt.)
Ignition system
Spark plugChampion: RV17YC
Spark plug gap0.89 mm (0.035 in)
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.

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