The Kawasaki FH721D is a 0.68 l (675 cc, 41.19 cu-in) V-twin 90° air-cooled 4-stroke internal combustion small gasoline motor with horisontal shaft, manufactured by Kawasaki Heavy Industries LTd., for general-purpose applications.
The FH721D has OHV (overhead valve design); cast-iron cylinder liners; twin-barrel, float type carburetor with fixed main jet; pulse type fuel pump; flywheel magneto transistor type ignition system; mechanical governor and low tone muffler.
The Kawasaki FH721D uses a full pressure lubrication system with spin-on oil filter and dual element air cleaner. The engine was equipped with BENDIX type electric starter and 12V-13A charging coil with a regulator.
The Kawasaki FH721D develops 25.3 PS (18.6 kW; 25.0 HP) at 3,600 rpm and 56.0 Nm (5.7 kg·m; 41.3 ft·lb) at 2,400 rpm of torque. It has a 75.2 mm (2.96 in) cylinder bore and 76.0 mm (2.99 in) piston stroke. Compression ratio rating is 8.1:1.
General information
| Engine Specifications | |
| Model | FH721D |
| Type | 4-stroke, OHV, V-twin 90° |
| Displacement | 675 cm 3 (41.2 cu-in) |
| Max. horsepower | 25.3 PS (18.6 KW; 25.0 HP) at 3,600 rpm |
| Max. torque (crank PTO) | 56.0 Nm (5.7 kg·m; 41.3 ft·lb) at 2,400 rpm |
| Carburetor | Twin barrel, float type |
| Cooling system | Air-cooling |
| Ignition system | Flywheel magneto transistor type |
| Lubricating system | Full pressure with spin-on oil filter |
| Starting system | Electric starter |
| Charging system | 12 Volt – 13A with regulator |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Fuel consumption | 245 g/HPh |
| Cooling system | Pressurized forced circulation type |
Dimensions and Weight
| Kawasaki FH721D | |
| Length, mm (in) | 447.5 (17.6) |
| Width, mm (in) | 430 (16.9) |
| Height, mm (in) | 492 (19.4) |
| Dry weight, kg (lb) | 44.0 (97.0) |
Tightening torque specs
| Tightening torque specs | Cylinder head | 28 Nm; 2.8 kg·m; 20.6 ft·lb |
| Connecting rod | 10 Nm; 1.0 kg·m; 7 ft·lb |
| Flywheel | 56 Nm; 5.7 kg·m; 41.3 ft·lb |
| Intake manifold | 6 Nm; 0.6 kg·m; 4.4 ft·lb |
| Valve clearance lock nut | 7 Nm; 0.7 kg·m; 5.1 ft·lb |
Maintenance data
| Engine | |
| Maximum speed | 3500 ± 100 rpm |
| Idle speed | 1500 ± 100 rpm |
| Cylinder compression | 3.9 kg/cm2 (56 psi) at 500 rpm |
| Valve clearance | |
| Intake valve | 0.10-0.15 mm (0.004-0.006 in) |
| Exhaust valve | 0.10-0.15 mm (0.004-0.006 in) |
| Oil system | |
| Oil type | 4-stroke or an equivalent (SF, SG, SH, or SJ ) |
| Recommended oil | SAE 10W-40, 10W-30, 5W-20 |
| Oil capacity (with filter changed) | 1.6 L |
| Ignition system | |
| Spark plug | NGK: BPR4ES |
| Spark plug gap | 0.75 mm (0.029 in) |
| Spark plug tightening torque | 22 Nm; 2.2 kg·m; 16.2 ft·lb |
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