Honda G80

Honda G80 engineThe Honda G80 is a 296 cc (18.0 single-cylinder air-coolled 4-stroke internal combustion small gasoline engine manufactured by Honda Motor Company since 1975 for general-purpose applications.

The Honda G80 engine has a slide valve (L-head) design and camshaft driven by a single row chain driven by the crankshaft. The engine has a recoil starter, horizontal carburetor with butterfly valve and high voltage ignition.

An 80.0 mm (3.2 in) cylinder bore and 59.0 mm (2.3 in) piston stroke give the engine a total of 296 cc (18.0 of displacement. The compression ratio was 6.3:1. The G80 produced 8.0 HP (5.9 kW) at 4000 rpm of maximum horsepower and continuous rated output was 6.0 HP (4.5 kW) at 3600 rpm. The maximum torque was 15.7 Nm (1.6 kg·m) at 2500 rpm. The dry weight of the Honda G80 engine was 30.4 kg (67.0 lbs).

General information

Engine Specifications
Model G80
Type 4-stroke, side valve type (L-head), single cylinder
Displacement 296 cm 3 (18.0 cu-in)
Max. horsepower 8.0 HP (5.9 kW) at 4,000 rpm
Max. torque 15.7 Nm (1.6 kg·m) at 2,500 rpm
Carburetor Horizontal, butterfly valve
Cooling system Forced-air
Ignition system High voltage ignition
Lubricating system Splash system
Starting system Recoil starter
Stoping system Ground switch
Fuel used Unleaded gasoline (octane number 86 or higher)
Fuel tank capacity 6.9 L (1.8 US gal., 1.5 Imp. gal.)
Fuel consumption 285 g/HPh
PTO shaft rotation Counterclockwise (from PTO shaft side)

Cylinder Block and Head

Cylinder block
Compression ratio: 6.3:1
Bore x Stroke 80 X 59 mm (3.2 x 2.3 in)
Sleeve internal diameter 80.00 mm (3.150 in)
Piston skirt outer diameter 79.97 mm (3.148 in)
Ring width Top 2.48 mm (0.098 in)
Second/Oil 2.49 mm (0.098 in)
Ring Side Clearance Top 0.02 mm (0.0008 in)
Second/Oil 0.01 mm (0.0004 in)
Piston pin outer diameter 19.0 mm (0.748 in)
Cylinder Head
Warpage (max) 0.2 mm (0.01 in)
Valve Arrangement: Side valve type (L-head)
Valves: 2
Stem outer diameter (standard): INTAKE 6.97 mm (0.274 in)
EXHAUST 6.93 mm (0.273 in)
Valve guide internal diameter 7.00 mm (0.276 in)
Cam height: INTAKE 35.18 mm (1.385 in)
EXHAUST 35.18 mm (1.385 in)

Maintenance data

Cylinder compression 4.0 kg/cm2 at 450-600 rpm
Tappet clearance
Intake valve 0.06-0.11 mm (0.0023-0.0043)
Exhaust valve 0.06-0.11 mm (0.0023-0.0043)
Oil system
Oil type Honda 4-stroke or an equivalent (SG, SF)
Recommended oil SAE 10W-30, 10W-40
Oil capacity 1.1 L (2.3 US pt, 1.9 lmp pt)
Ignition system
Ignition timing 25 ° B.T.D.C (Fixed)
Spark plug NGK: BR6HS, B6HS
Spark plug gap 0.6-0.7 mm (0.024-0.028 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 (10 mm bolt) 35-40 Nm; 3.5-4.0 kg·m; 25.3-28.9 ft·lb
Cylinder Head (10 mm bolt) 35-40 Nm; 3.5-4.0 kg·m; 25.3-28.9 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
Muffler (8 mm bolt) 20-28 Nm; 2.0-2.8 kg·m; 14.5-20.2 ft·lb
Carburetor (6 mm nut) 8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb
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