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.
|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|
|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
|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|
|Maximum speed||3500 ± 100 rpm|
|Idle speed||1500 ± 100 rpm|
|Cylinder compression||3.9 kg/cm2 (56 psi) at 500 rpm|
|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 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|
|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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