Kohler TH650

Kohler TH650The Kohler TH650 is a 653 cc (39.8 cu·in) natural aspirated V-twin four-stroke air-cooled internal combustion small gasoline engine from the Triad series with a horizontal shaft, manufactured by Kohler Co for general-purpose applications.

The cylinder bore and the piston stroke are 80.0 mm (3.15 in) and 65.0 mm (2.56 in), respectively. Compression ratio rating is 8.8:1.

The Kohler TH650 engine produced 20.3 PS (14.9 KW; 20.0 HP) at 3,600 rpm of horsepower and 45.1 Nm (4.6 kg·m; 33.3 ft·lb) at 2,500 rpm of torque.

The Kohler TH650 features:

  • OHC design
  • Cast iron cylinder liners
  • Electronic ignition system (CDI)
  • Carburetor with fixed main jet
  • Mechanical centrifugal governor
  • Full pressure lubrication system
  • Forced air cooling system
  • Recoil or electric starter

General information

Engine Specifications
Engine modelTriad TH650
Engine type4-stroke, OHV, V-Twin
Displacement653 cm 3 (39.8 cu-in)
Max. horsepower20.3 PS (14.9 KW; 20.0 HP) at 3,600 rpm
Max. torque45.1 Nm (4.6 kg·m; 33.3 ft·lb) at 2,500 rpm
Cooling systemForced air
Air cleanerReplaceable high-density paper element
Lubricating systemFull pressure
Ignition systemElectronic ignition system (CDI)
Fuel systemCarburetor with fixed main jet
Fuel usedUnleaded gasoline (octane number 86 or higher)
Starting systemRecoil or electric starter
GovernorMechanical centrifugal governor
PTO shaft rotationCounterclockwise (from PTO shaft side)
Dimensions (L x W X H)328 x 400 x 449 mm (12.9 x 15.7 x 17.7 in)
Dry weight43.0 kg (90.0 lbs)

Cylinder Block and Head

Cylinder block
Compression ratio:8.8:1
Cylinder bore:80.0 mm (3.15 in)
Piston stroke:65.0 mm (2.56 in)
Cylinder head
Valve arrangement:OHC, belt driven
Valves:4 (2 per cylinder)
Valve head diameter (INTAKE):29.180-29.430 mm (1.1488-1.1586 in)
Valve head diameter (EXHAUST):26.300-26.700 mm (1.0354-1.0512 in)
Valve seat angle (INTAKE):89°
Valve seat angle (EXHAUST):89°
Valve seat angle (INTAKE):45°
Valve seat angle (EXHAUST):45°
Valve steam diameter (INTAKE):5.982-6.000 mm (0.2355-0.2362 in)
Valve steam diameter (EXHAUST):5.970-5.988 mm (0.2350-0.2357 in)
Valve lift minimal (INTAKE):7.50 mm (0.295 in)
Valve lift minimal (EXHAUST):7.50 mm (0.295 in)

Tightening torque specs

Tightening torque specs
Connecting rod11.3 Nm (1.2 kgf·m; 8.3 ft·lb)
Electric starter7.9 Nm (0.8 kgf·m; 5.8 ft·lb)
Oil drain plug16.3 Nm (1.7 kgf·m; 12.0 ft·lb)
Oil filter5.6-9.0 Nm (0.6-0.9 kgf·m; 4.1-6.6 ft·lb)
Muffler retaining nuts24.4 Nm (2.5 kgf·m; 18 ft·lb)
Valve cover5.6 Nm (0.6 kgf·m; 4.1 ft·lb)
Flywheel66.4 Nm (6.77 kg·m; 49 ft·lb)
Spark plug24.4-29.8 Nm (2.5-3 kgf·m; 18-22 ft·lb)
Ignition module4.0-6.2 Nm (0.4-0.6 kgf·m; 3-4.6 ft·lb)

Service Data

Maximum speed:3600±50 rpm
Valve clearance
Intake0.013-0.064 mm (0.0005-0.0025 in)
Exhaust0.076-0.127 mm (0.0030-0.0050 in)
Oil system
Lubrication system:Full pressure
Oil type:API SG, SH, SJ, or higher
Recommended oil:SAE 10W-30
Oil capacity:1.4 liters (1.48 US.qts, 1.23 Imp. qts)
Fuel system
Type:Carburetor with fixed main jet
Fuel pump:Pulse type
Fuel filter:In-line
Ignition system
Type:Electronic ignition (CDI)
Spark plug:Champion RC12YC
Spark plug gap:0.76 mm (0.030 in)
Ignition module air gap0.200-0.300 mm (0.0079-0.0118 in)


1. Kohler OHC 16,18 HP horizontal crankshaft service manual. Kohler Co. 1997.
2. Kohler Triad OHC TH520-TH650 horizontal crankshaft owner’s manual. Kohler Co. 2004.

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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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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