Honda G80

The Honda G80 is a 296 cc (18.0 cu.in.) 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 cu.in.) 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

Engine
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