Honda G100 K1

Honda G100 K1 2.2 HPThe Honda G100 K1 is a 83 cc (5.06 single-cylinder air-coolled 4-stroke internal combustion small gasoline engine manufactured by Honda Motor Company since 1980. The G100 K1 is the second generation of this engine. It has larger cylinder bore and, as a result, larger displacement.

The Honda G100 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.

There are three versions of G100 engine:

  • Honda G100, with 76 cc of displacement and 2.0 HP or 2.2 HP of horsepower
  • Honda G100 K1, with 83 cc of displacement and 2.2 HP
  • Honda G100 K2, with 98 cc of displacement and 2.5 HP of maximum output power

The G100K1 engine a compression ratio rating is 6.5:1, cylinder bore and piston stroke are 48.0 mm (1.88 in) and 46.0 mm (1.81 in), respectively.

The Honda G100 K1 produced 2.2 HP (1.64 kW) at 4200 rpm of maximum horsepower and 3.8 Nm (0.38 kg·m) of torque.

General information

Engine Specifications
Model G100 K1
Type 4-stroke, side valve type (L-head), single cylinder
Displacement 83 cm 3 (5.06 cu-in)
Max. horsepower 2.2 HP (1.64 kW) at 4200 rpm
Max. torque 3.8 Nm (0.38 kg·m)
Carburetor Horizontal, butterfly valve
Cooling system Forced-air
Ignition system Transistorized magneto or CDI
Lubricating system Splash system
Starting system Recoil starter
Stoping system Ground of primary circuit
Fuel used Unleaded gasoline (octane number 86 or higher)
Fuel tank capacity 1.4 L
Fuel consumption 320 g/HPh
PTO shaft rotation Counterclockwise (from PTO shaft side)

Cylinder Block and Head

Cylinder block
Compression ratio: 6.5:1
Bore x Stroke 48 x 46 mm (1.88 in x 1.81 in in)
Sleeve internal diameter 48.00 mm (1.88 in)
Piston skirt outer diameter 47.995 mm (1.8503 in)
Number of piston rings (compression / oil): 2 / 1
Ring side clearance Top/second/oil 0.01-0.05 mm (0.0004-0.002 in)
Ring end gap Top/second 0.25 mm (0.009 in)
Oil 0.45 mm (0.017 in)
Connecting rod small end ID 10.0 mm (0.393 in)
Connecting rod big end ID 18.0 mm (0.708 in)
Crankpin outer diameter 17.98 mm (0.707 in)
Cylinder Head
Warpage (limit) 0.10 mm (0.004 in)
Valve Arrangement: Side valve type (L-head)
Valves: 2
Stem outer diameter (standard): INTAKE 5.490 mm (0.2161 in)
EXHAUST 5.445 mm (0.2143 in)
Guide internal diameter INTAKE / EXHAUST 5.5 mm (0.2165 in)
Spring free length 27.1 mm (1.066 in)
Cam height: INTAKE 20.82 mm (0.8196 in)
EXHAUST 20.82 mm (0.8196 in)
Camshaft journal diameter: 12.184 mm (0.4796 in)

Maintenance data

Idle speed 1400 ± 110 rpm
Cylinder compression 6.5 kg/cm2 (637 kPa) at 800 rpm
Adjust timing ignition
Ignition timing 20° B.T.D.C. (Fixed)
Adjust valve clearance
Intake valve 0.08-0.16 mm (0.0031-0.0063 in)
Exhaust valve 0.08-0.16 mm (0.0031-0.0063 in)
Oil system
Oil type Honda 4-stroke “SE”
Recommended oil 10W-40
Oil capacity 0.45 L
Main jet #62
Ignition system
Spark plug NGK: BM4A, BMR4A
Spark plug gap 0.6-0.7 mm (0.024-0.028 in)
Primary ignition coil resistance 0.7-0.9 kΩ
Secondary ignition coil resistance 6.3-7.7 kΩ

Tightening torque specs

Tightening torque specs
Carburetor 4-6 Nm; 0.4-0.6 kg·m; 2.9-4.3 ft·lb
Flywheel 45-55 Nm; 4.5-5.5 kg·m; 32.5-40 ft·lb
Governor arm 8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb
Cylinder head 8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb
Crankcase cover 8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb
Connecting rod 4-6 Nm; 0.4-0.6 kg·m; 2.9-4.3 ft·lb
5 mm bolts, nuts 4-7 Nm; 0.4-0.7 kg·m; 2.9-5.1 ft·lb
6 mm bolts, nuts 8-12 Nm; 0.8-1.2 kg·m; 5.8-8.7 ft·lb
8 mm bolts, nuts 20-28 Nm; 2.0-2.8 kg·m; 14.5-20.3 ft·lb
10 mm bolts, nuts 35-40 Nm; 3.5-4.0 kg·m; 25-29 ft·lb
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We try to use verified sources and official documentation, however, differences between sources or errors in entering information may occur. We do not provide advice on technical issues related to the engines operation or repair. We do not recommend using provided information for engines repairing engines or spare parts ordering, use only official service manuals and spare-parts catalogs.


    • Hi just wandering on a honda G100 K1 engine what size is the PTO shaft please I’m interested in buying one just wanted to check if it’s suitable?

  1. Hello there I’m interested in purchasing a Honda G100 2.2 hp engine just wandering what size shaft it is please

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