Honda GS65

Honda GS65 engineThe Honda GS65 is a 240 cc single-cylinder air-coolled 4-stroke internal combustion small gasoline engine manufactured by Honda Motor Company since 1975 for general-purpose applications.

The Honda GS65 engine has a slide valve (L-head) design and camshaft driven by a single row chain driven by the crankshaft. It has an electric starter motor, horizontal carburetor with butterfly valve and high voltage ignition.

The GS65 produced 6.8 PS (5.0 kW) at 4000 rpm of maximum output and 12.2 Nm (1.24 kg·m) at 3000 rpm. The dry weight of the Honda GS65 engine was 30.0 kg (66.0 lbs). A 72 mm (2.8 in) cylinder bore and 59 mm (2.3 in) piston stroke give the engine a total of 240 cc (14.6 of displacement. The compression ratio is 6.1:1.

General information

Engine Specifications
Type4-stroke, side valve type (L-head), single cylinder
Displacement240 cm 3 (14.6 cu-in)
Max. horsepower6.8 HP (5.0 kW) at 4000 rpm
Max. torque12.0 Nm (1.24 kg·m) at 3000 rpm
CarburetorHorizontal, butterfly valve
Cooling systemForced-air
Ignition systemHigh voltage ignition
Lubricating systemSplash system
Starting systemElectirc starter motor
Stoping systemGround switch
Fuel usedUnleaded gasoline (octane number 86 or higher)
Fuel tank capacity6.9 L (1.6 US gal., 1.5 Imp. gal.)
Fuel consumption300 g/HPh (0.67 lb/HPh)
PTO shaft rotationCounterclockwise (from PTO shaft side)

Cylinder Block and Head

Cylinder block
Compression ratio:6.1:1
Bore x Stroke72 X 59 mm (2.8 x 2.3 in)
Sleeve internal diameter72.00 mm (2.835 in)
Piston skirt outer diameter71.97 mm (2.833 in)
Ring widthTop2.48 mm (0.098 in)
Second/Oil2.49 mm (0.098 in)
Ring Side ClearanceTop0.02 mm (0.0008 in)
Second/Oil0.01 mm (0.0004 in)
Piston pin outer diameter19.0 mm (0.748 in)
Cylinder Head
Warpage (max)0.2 mm (0.01 in)
Valve Arrangement:OHV
Stem outer diameter (standard):INTAKE6.97 mm (0.274 in)
EXHAUST6.93 mm (0.273 in)
Valve guide internal diameter7.00 mm (0.276 in)
Cam height:INTAKE35.18 mm (1.385 in)
EXHAUST35.18 mm (1.385 in)

Tightening torque specs

Tightening torque specs
Fuel tank (8 mm nut, bolt)20-28 Nm; 2.0-2.8 kg·m; 14.5-20.2 ft·lb
Side cover (8 mm bolt)20-25 Nm; 2.0-2.5 kg·m; 14.5-18.1 ft·lb
Cylinder Head (8 mm bolt)20-25 Nm; 2.0-2.5 kg·m; 14.5-18.1 ft·lb
Cylinder (6 mm bolt)8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb
Cylinder (8 mm bolt)20-28 Nm; 2.0-2.8 kg·m; 14.5-20.2 ft·lb
Camshaft center (6 mm bolt)10-15 Nm; 1.0-1.5 kg·m; 7.2-10.8 ft·lb
Starter pulley (6 mm bolt)8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb
Flywheel (17 mm nut)70-80 Nm; 7.0-8.0 kg·m; 50.6-57.9 ft·lb
Muffler (6 mm nut)8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb
Carburetor (6 mm nut)8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb

Maintenance data

Cylinder compression4.0 kg/cm2 at 450-600 rpm
Tappet clearance
Intake valve0.06-0.11 mm (0.0023-0.0043)
Exhaust valve0.06-0.11 mm (0.0023-0.0043)
Oil system
Oil typeHonda 4-stroke or an equivalent (SG, SF)
Recommended oilSAE 10W-30, 10W-40
Oil capacity0.82 L (1.7 US pt., 1.4 Imp. pt.)
Ignition system
Ignition timing25 ° B.T.D.C (Fixed)
Spark plugNGK: BR6HS, B6HS
Spark plug gap0.6-0.7 mm (0.024-0.028 in)
Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

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