The Kawasaki FH641D is a 0.68 l (675 cc, 41.19 cu-in) V-twin 90° air-cooled 4-stroke internal combustion small gasoline motor with horizontal shaft, manufactured by Kawasaki Heavy Industries LTd., for general-purpose applications.
The FH641D 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 FH641D 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 FH641D develops 21.4 PS (15.7 kW; 21.0 HP) at 3,600 rpm and 52.1 Nm (5.3 kg·m; 38.4 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 | FH641D |
Type | 4-stroke, OHV, V-twin 90° |
Displacement | 675 cm 3 (41.2 cu-in) |
Max. horsepower | 21.4 PS (15.7 KW; 21.0 HP) at 3,600 rpm |
Max. torque (crank PTO) | 52.1 Nm (5.3 kg·m; 38.4 ft·lb) at 2,400 rpm |
Carburetor | Twin barrel, float type |
Cooling system | Air-cooled |
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 FH641D | |
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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