Kawasaki FH641D

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