Honda G150

Honda G150 engineThe Honda G150 is a 144 cc (8.8 single-cylinder air-coolled 4-stroke internal combustion small gasoline engine manufactured by Honda Motor Company since 1977 for general-purpose applications.

The Honda G150 engine has a slide valve (L-head) design and camshaft driven by a single row chain driven by the crankshaft. The engine has an electric or recoil starter, horizontal carburetor with butterfly valve and transistorized magneto or contact point breaker (CDI) ignition system.

The G150 engine a compression ratio rating is 6.5:1, cylinder bore and piston stroke are 64.0 mm (2.52 in) and 45.0 mm (1.77 in), respectively.

The G150 produced 3.5 HP (2.6 kW) at 3600 rpm of maximum horsepower for CDI ignition models or 3.8 HP (2.8 kW) at 3600 rpm for models with transistorized magneto ignition.

General information

Engine Specifications
Type4-stroke, side valve type (L-head), single cylinder
Displacement144 cm 3 (8.8 cu-in)
Max. horsepower 3.5 HP (2.6 kW) at 3600 PRM (CDI)
3.8 HP (2.8 kW) at 3600 PRM (Magneto ignition)
Max. torque Crankshaft PTO type:
7.1 Nm (0.72 kg·m) at 3000 PRM (CDI)
7.4 Nm (0.76 kg·m) at 3000 PRM (Magneto ignition)
Camshaft PTO type:
14.2 Nm (1.44 kg·m) at 1500 PRM (CDI)
14.8 Nm (1.52 kg·m) at 1500 PRM (Magneto ignition)
CarburetorHorizontal, butterfly valve
Cooling systemForced-air
Ignition systemTransistorized magneto or CDI
Lubricating systemSplash system
Starting systemRecoil starter
Stoping systemGround of primary circuit
Fuel usedUnleaded gasoline (octane number 86 or higher)
Fuel tank capacity2.5 L (0.66 US gal, 0.55 Imp gal.)
Fuel consumption310 g/HPh
PTO shaft rotationCounterclockwise (from PTO shaft side)

Cylinder Block and Head

Cylinder block
Compression ratio:6.5:1
Bore x Stroke64 X 45 mm (2.52 x 1.77 in)
Sleeve internal diameter64.00 mm (2.52 in)
Piston skirt outer diameter64.00 mm (2.52 in)
Number of piston rings (compression / oil):2 / 1
Ring side clearanceTop/second/oil0.01-0.05 mm (0.0004-0.002 in)
Ring end gapTop/second0.2-0.4 mm (0.008-0.016 in)
Oil0.2-0.4 mm (0.008-0.016 in)
Ring widthTop/second2.0 mm (0.08 in)
Oil3.0 mm (0.12 in)
Connecting rod small end ID15.0 mm (0.059 in)
Connecting rod big end ID26.0 mm (1.023 in)
Crankpin outer diameter26.0 mm (1.02 in)
Cylinder Head
Warpage (limit)0.10 mm (0.004 in)
Valve Arrangement:Side valve type (L-head)
Stem outer diameter (standard):INTAKE7.0 mm (0.28 in)
EXHAUST7.0 mm (0.28 in)
Guide internal diameterINTAKE / EXHAUST7.0 mm (0.28 in)
Spring free length36.7 mm (1.44 in)
Cam height:INTAKE33.5 mm (1.32 in)
EXHAUST33.8 mm (1.33 in)
Camshaft journal diameter:17.8 mm (0.70 in)

Maintenance data

Maximum speed3850 ± 150 rpm
Idle speed1400 ± 150 rpm
Cylinder compression6.0 kg/cm2 (85 psi)
Adjust timing ignition
Ignition timing 24° B.T.D.C. – for magneto ignition
20° B.T.D.C. (Fixed) – Contact breaker point
The CDI type does not require adjustment.
Adjust valve clearance
Intake valve0.08-0.16 mm (0.0031-0.0063 in)
Exhaust valve0.16-0.24 mm (0.0063-0.0094 in)
Oil system
Oil typeHonda 4-stroke “SE”
Recommended oil10W-40
Oil capacity0.7 L (1.5 US pt. 1.2 Imp. pt.)
Main jet#70
Float height8.2 mm (0.32 in)
Pilot screw opening1-5/8 turns out
Ignition system
Spark plug NGK: B4H, BR4HS
Spark plug gap0.6-0.7 mm (0.024-0.028 in)
Spark plug cap resistance10 kΩ
Ignition coil (Contact breaker piont type)
Resistance in secondary coil6.6 kΩ
Ignition coil (Transistorized magneto type)
Primary ignition coil resistance0.9 kΩ
Secondary ignition coil resistance6.5 kΩ
Ignition coil air gap0.3 ± 0.1 (0.012 ± 0.004)

Tightening torque specs

Tightening torque specs
Air cleaner case nut (M6x10)10 Nm; 1.0 kg·m; 7 ft·lb
Air cleaner case bolt (M6x70)2.5 Nm; 0.25 kg·m; 1.8 ft·lb
Connecting rod bolt (M7x35)12 Nm; 1.2 kg·m; 8.6 ft·lb
Cylinder head bolt (M8x45)25 Nm; 2.5 kg·m; 18 ft·lb
Cylinder barrel stud (M8)4 Nm; 0.4 kg·m; 2.9 ft·lb
Crankcase cover bolt (M6x32)10 Nm; 1.0 kg·m; 7 ft·lb
Control lever bolt (M6x12)10 Nm; 1.0 kg·m; 7 ft·lb
Fan cover (M6x12)10 Nm; 1.0 kg·m; 7 ft·lb
Flywheel nut (M14x1.5)75 Nm; 7.5 kg·m; 54 ft·lb
Fuel cock bolt (M6x12)10 Nm; 1.0 kg·m; 7 ft·lb
Fuel tank bolt, nut (M6x10)10 Nm; 1.0 kg·m; 7 ft·lb
Ignition coil bolt (M6x32)10 Nm; 1.0 kg·m; 7 ft·lb
Muffler mounting nut (M8x12.5)12 Nm; 1.2 kg·m; 8.6 ft·lb
Muffler protector mounting nut (M6x8)5 Nm; 0.5 kg·m; 3.6 ft·lb
Oil drain bolt (M12)20 Nm; 2.0 kg·m; 14.5 ft·lb
Side plate (M6x12)10 Nm; 1.0 kg·m; 7 ft·lb
Shroud (M6x12)10 Nm; 1.0 kg·m; 7 ft·lb
Tappet room cover bolt (M6x12)14 Nm; 1.4 kg·m; 10 ft·lb
5 mm bolts, nuts5.5 Nm; 0.55 kg·m; 4.0 ft·lb
6 mm bolts, nuts10 Nm; 1.0 kg·m; 7 ft·lb
8 mm bolts, nuts24 Nm; 2.4 kg·m; 17 ft·lb
10 mm bolts, nuts37 Nm; 3.7 kg·m; 27 ft·lb
12 mm bolts, nuts55 Nm; 5.5 kg·m; 39.5 ft·lb
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