Kohler M8

The Kohler M8 is a 305 cc (18.64 cu·in) single-cylinder air-cooled four-stroke internal combustion gasoline engine from the Magnum-series, manufactured by Kohler Co.

The Kohler M8 engine has an L-head (side valve) design and a horizontal PTO shaft. This engine is equipped with the Kohler-build side-draft carburetor with an adjustable jet and an electronic magneto ignition system. The M8 engine used a high-density paper air cleaner.

The cylinder bore is 74.7 mm (2.94 in) and the piston stroke is 69.85 mm (2.75 in). The compression ratio rating is 6.8:1.

The Kohler M8 engine produced 8.2 PS (6.0 KW; 8.0 HP) at 3,600 rpm of horsepower.

The breakdown of the engine code is as follows:

• M – M-series
• 8 – 8.0 HP horsepower
• Suffix (engine is available with the following options):
  S – Electric starter;
  T – Retractable starter;
  ST – Electric and retractable starter;
  G – Tapered crankshaft (Generator applications);
  P – Threaded crankshaft (Pump applications);
  R – Reduction gear unit;
  EP – Generator;

General information

Engine Specifications
Model	Magnum M8
Type	4-stroke, L-head, single cylinder
Displacement	305 cm 3 (18.64 cu-in)
Max. horsepower	8.2 PS (6.0 KW; 8.0 HP) at 3,600 rpm
Max. torque (crank PTO)	–
Fuel system	Side-draft carburetor
Cooling system	Forced-air
Ignition system	Electronic magneto ignition system
Lubricating system	Splash type
Starting system	Recoil or electric starter
Fuel used	Unleaded gasoline (octane number 86 or higher)
Fuel tank capacity	4.7 liters (1.25 US gal, 1.0 Imp. gal)
Weight	32.2 kg (71.0 lbs)

Cylinder Block and Head

Cylinder block
Compression ratio:		6.8:1
Bore x Stroke		74.7 X 69.85 mm (2.94 x 2.75 in)
Sleeve internal diameter		74.5998-74.6252 mm (2.9370-2.9370 in)
Number of piston rings (compression / oil):		2 / 1
Style A
Piston skirt outer diameter		74.3737-74.4144 mm (2.9281-2.9297 in)
Ring end gap	Top	0.178-0.432 mm (0.007-0.017 in)
	Second	0.178-0.432 mm (0.007-0.017 in)
Style C and D
Piston skirt outer diameter		74.4957-74.5134 mm (2.9329-2.9336 in)
Ring end gap	Top	0.254-0.584 mm (0.010-0.023 in)
	Second	0.254-0.584 mm (0.010-0.023 in)
Connecting rod small end ID		15.8877-15.8953 mm (0.6255-0.6258 in)
Piston pin outer diameter		15.8674-15.8725 mm (0.6247-0.6249 in)
Cylinder Head
Valve Arrangement:		L-head (sidevalve)
Valves:		2
Valve minimum lift – Zero lash:	INTAKE	6.90 mm (0.2718 in)
	EXHAUST	6.30 mm (0.2482 in)
Stem outer diameter (standard):	INTAKE	7.887-7.899 mm (0.3105-0.3110 in)
	EXHAUST	7.833-7.851 mm (0.3084-0.3091 in)

Tightening torque specs

Tightening torque specs
Cylinder head bolt	34-41 Nm; 3.5-4.2 kg·m; 25-30 ft·lb
Spark plug	25-30 Nm; 2.55-3.06 kg·m; 18-22 ft·lb

Service Information

Engine
Max speed	3,600 rpm
Valve clearance
Intake valve clearance	0.15-0.20 mm (0.0060-0.0079 in)
Exhaust valve clearance	0.43-0.48 mm (0.0169-0.0189 in)
Oil system
Oil type	API SF or SG
Recommended oil	Summer: SAE 30W Winter: SAE 5W-20, 5W-30
Oil capacity	0.95 liters (1 US.qts, 0.84 Imp. qts)
Ignition system
Spark plug	Champion: RCJ-8
Spark plug gap	0.65 mm (0.0256 in)
Ignition module air gap	0.30-0.40 mm (0.012-0.016 in)