The Kohler ZT720 is a 725 cc (44.2 cu·in) natural aspirated V-twin four-stroke air-cooled internal combustion small gasoline engine from the Confidant series with a vertical shaft, manufactured by Kohler Co for general-purpose applications.
A 83.0 mm (3.27 in) cylinder bore and 67.0 mm (2.64 in) piston stroke give the ZT720 engine a total of 725 cc of displacement. The compression ratio rating is 9.1:1.
The ZT720 engine produced 21.4 PS (15.7 KW; 21.0 HP) at 3,600 rpm of maximum horsepower and 55.2 Nm (5.63 kg·m; 40.74 ft·lb) at 2,200 rpm of maximum torque.
The Kohler ZT720 features:
- High-impact nylon shroud and valve cover
- OHV design
- Aluminum cylinder block
- Cast iron cylinder liners
- Electronic ignition system
- Carburetor with fixed main jet (Walbro or Keihin)
- Mechanical centrifugal governor
- Full pressure lubrication system
- Forced air cooling system
- Electric or recoil starter
General information
| Engine Specifications | |
| Engine model | Confidant ZT720 |
| Engine type | 4-stroke, OHV, V-twin |
| Displacement | 725 cm3, (44.24 cu·in) |
| Max. horsepower | 21.4 PS (15.7 KW; 21.0 HP) at 3,600 rpm |
| Max. torque | 55.2 Nm (5.63 kg·m; 40.74 ft·lb) at 2,200 rpm |
| Cooling system | Forced air |
| Air cleaner | Heavy-duty air cleaner |
| Lubricating system | Full pressure |
| Ignition system | Electronic ignition system |
| Fuel system | Carburetor with fixed main jet (Walbro or Keihin) |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Starting system | Electric or recoil starter |
| Governor | Mechanical centrifugal governor |
| PTO shaft rotation | Counterclockwise (from PTO shaft side) |
| Dimensions (L x W X H) | 478 x 443 x 431 mm (18.8 × 17.5 × 17.0 in) |
| Dry weight | 41.3 kg (91.0 lbs) |
Cylinder Block and Head
| Cylinder block | |
| Compression ratio: | 9.1:1 |
| Cylinder bore: | 83.0 mm (3.27 in) |
| Piston stroke: | 67.0 mm (2.64 in) |
| Cylinder internal diameter (standard): | 82.988-83.013 mm (3.2672-3.2682 in) |
| Thrust face outer diameter (standard): | 82.978 mm (3.2668 in) |
| Piston pin diameter: | 16.995-17.000 mm (0.6691-0.6693 in) |
| Number of piston rings (compression / oil): | 2/1 |
| Side clearance (Top): | 0.030-0.070 mm (0.0010-0.0026 in) |
| Side clearance (Second): | 0.030-0.070 mm (0.0010-0.0026 in) |
| Side clearance (Oil): | 0.060-0.190 mm (0.0022-0.0073 in) |
| Ring end gap (Top): | 0.189-0.277 mm (0.0074-0.0109 in) |
| Ring end gap (Second): | 1.519-1.797 mm (0.0598-0.0708 in) |
| Number of main bearings: | 2 |
| Crankshaft main journal diameter: | 40.913-40.935 mm (1.6107-1.6116 in) |
| Crankpin journal diameter: | 35.950-35.974 mm (1.4154-1.4163 in) |
| Cylinder head | |
| Valve arrangement: | OHV, gear driven |
| Valves: | 2 (4 valves in total) |
| Valve head diameter (INTAKE): | 33.370-33.630 mm (1.3138-1.324 in) |
| Valve head diameter (EXHAUST): | 29.370-29.630 mm (1.1563-1.1665 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): | 6.982-7.000 mm (0.2749-0.2756 in) |
| Valve steam diameter (EXHAUST): | 6.970-6.988 mm (0.2744-0.2751 in) |
| Valve lift minimal (INTAKE): | 8.500 mm (0.3346 in.) |
| Valve lift minimal (EXHAUST): | 8.500 mm (0.3346 in.) |
| Camshaft journal diameter: | 19.948-19.960 mm (0.7854-0.7858 in) |
Tightening torque specs
| Tightening torque specs | |
| Intake manifold mounting (torque in 2 increments) | Step 1: 7.4 Nm (0.75 kg·m; 5.5 ft·lb) Step 2: 9.9 Nm (1.00 kg·m; 7.3 ft·lb) |
| Cylinder head bolt (torque in 2 increments) | Step 1: 22.6 Nm (2.31 kg·m; 16.7 ft·lb) Step 2: 41.8 Nm (4.26 kg·m; 30.8 ft·lb) |
| Rocker arm stud | 11.3 Nm (1.2 kgf·m; 8.3 ft·lb) |
| Rocker arm adjuster setscrew | 7.9 Nm (0.8 kgf·m; 5.8 ft·lb) |
| Connecting rod cap | Black Coating: 11.3 Nm (1.2 kgf·m; 8.3 ft·lb) Gray Metallic Coating: 13.6 Nm (1.4 kgf·m; 10.0 ft·lb) |
| Flywheel retaining screw | 74.5 Nm (7.6 kgf·m; 55.0 ft·lb) |
| Governor lever nut | 6.8 Nm (0.7 kgf·m; 5.0 ft·lb) |
| Oil drain plug | 13.6 Nm (1.4 kgf·m; 10.0 ft·lb) |
| Spark plug | 27.0 Nm (2.75 kg·m; 20.0 ft·lb) |
Service Data
| Engine | |
| Maximum speed: | 3600±50 rpm |
| Idle speed: | 1200±75 rpm |
| Compression pressure | |
| Standard: | 1.1 MPa (160 psi) |
| Compression differential limit between cylinders: | 15% and less |
| Oil system | |
| Lubrication system: | Full pressure |
| Oil type: | API SG, SH, SJ, or higher |
| Recommended oil: | SAE 10W-30 |
| Oil capacity: | W/o oil filter: 1.7 L (1.8 US. qt, 1.5 Imp. qt.) With oil filter: 1.9 L (2.0 US.qts, 1.7 Imp. qts) |
| Fuel system | |
| Type: | Carburetor with fixed main jet (Walbro or Keihin) |
| Fuel pump: | Pulse type |
| Fuel filter: | In-line |
| Ignition system | |
| Type: | Electronic ignition system |
| Spark plug: | Champion RC12YC |
| Spark plug gap: | 0.76 mm (0.030 in) |
| Ignition coil air gap | 0.203-0.305 mm (0.008-0.012 in) |
References
1. Kohler Confidant ZT710-ZT740 service manual. Kohler Co. 2021.
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