Honda GXH50

Honda GXH50The Honda GXH50 is a small (49 cc, 2.99 cu-in) single-cylinder air-cooled 4-stroke internal combustion gasoline engine with horizontal shaft, manufactured by Honda Motor Company, for general-purpose applications, such as construction and industrial equipment; agricultural equipment; water pumps.

This engine has a single-cylinder, overhead-valve, and precision camshaft design; high compression ratio for better fuel efficiency; ball bearing supported crankshaft for greater stability; large capacity, multi-chamber exhaust system. The Honda GXH50 engine is equipped with transistorized magneto ignition, float type carburetor and recoil starter.

The GXH50 motor a compression ratio rating is 8.0:1, cylinder bore and piston stroke are 41.8 mm (1.65 in) and 36.0 mm (1.42 in), respectively. The Honda GXH50 engine produces 2.5 PS (1.8 kW) at 7,000 rpm and 3.04 N·m (0.31 kg·m, 2.25 ft·lb) at 4,500 rpm of torque.

General information

Engine Specifications
Model GXH50
Type 4-stroke, OHV, single cylinder
Displacement 49 cm 3 (2.99 cu-in)
Max. horsepower Net: 2.1 HP (1.6 kW) at 7,000 rpm
Gross: 2.5 PS (1.8 kW) at 7,000 rpm
Max. torque (crank PTO) Net: 2.7 N·m (0.27 kg·m, 2.0 ft·lb) at 4,500 rpm
Gross: 3.04 N·m (0.31 kg·m, 2.25 ft·lb) at 4,500 rpm
Carburetor Float type
Cooling system Forced-air
Ignition system Transistorized magneto ignition
Lubricating system Splash
Starting system Recoil starter
Stoping system Ignition primary circuit ground
Fuel used Unleaded gasoline (octane number 86 or higher)
Fuel tank capacity 1.2 L (0.32 US gal, 0.26 Imp gal)
Fuel consumption 240 g/HPh
PTO shaft rotation Counterclockwise (from PTO shaft side)

Cylinder Block and Head

Cylinder block
Compression ratio: 8.0:1
Bore x Stroke 41.8 mm X 36 mm (1.65 x 1.42 in)
Sleeve internal diameter 41.800-41.815 mm (1.6445-1.6463 in)
Piston skirt outer diameter 41.770-41.790 mm (1.6445-1.6453 in)
Ring side clearance Top/second 0.015-0.050 mm (0.0006-0.0020 in)
Ring end gap Top 0.15-0.30 mm (0.0059-0.0118 in)
Second 0.15-0.30 mm (0.0059-0.0118 in)
Ring width Top 0.77-0.79 mm (0.030-0.031 in)
Second 0.97-0.99 mm (0.038-0.039 in)
Connecting rod small end ID 10.006-10.007 mm (0.3939-0.3944 in)
Connecting rod big end ID 15.000-15.011 mm (0.5906-0.5910 in)
Crankpin outer diameter 14.973-14.984 mm (0.5895-0.5899 in)
Cylinder Head
Warpage (limit) 0.10 mm (0.004 in)
Valve Arrangement: OHV
Valves: 2
Stem outer diameter (standard): INTAKE 3.970-3.985 mm (0.1563-0.1569 in)
EXHAUST 3.935-3.950 mm (0.1549-0.1555 in)
Spring free length 23.7.0 mm (0.93 in)
Cam height 27.972 mm (1.1013 in)

Tightening torque specs

Tightening torque specs
Spark plug 12 Nm; 1.2 kg·m; 8.6 ft·lb
Connecting rod bolt 6 Nm; 0.6 kg·m; 4.3 ft·lb
Crankcase cover bolt 7.5 Nm; 0.75 kg·m; 5.4 ft·lb
Oil case bolt 7.5 Nm; 0.75 kg·m; 5.4 ft·lb
Flywheel nut 22 Nm; 2.2 kg·m; 16 ft·lb
Igniton coil bolt 6 Nm; 0.6 kg·m; 5 ft·lb
Carburetor drain screw 1.2 Nm; 0.12 kg·m; 0.9 ft·lb
Carburetor drain bolt 4.5 Nm; 0.45 kg·m; 3.3 ft·lb
4 mm bolts, nuts 3.5 Nm; 0.35 kg·m; 2.5 ft·lb
5 mm bolts, nuts 5.5 Nm; 0.55 kg·m; 4.0 ft·lb
6 mm bolts, nuts 10 Nm; 1.0 kg·m; 7 ft·lb

Service Information

Maximum speed 7,800 ± 150 rpm
Idle speed 2,500 ± 200 rpm
Cylinder compression 4.3 kg/cm2 (61 psi) at 1000 rpm
Valve clearance
Intake valve 0.06-0.10 mm (0.0024-0.0039 in)
Exhaust valve 0.09-0.13 mm (0.0035-0.0051 in)
Oil system
Oil type Honda 4-stroke or an equivalent (SE or SF)
Recommended oil SAE 10W-30
Oil capacity 0.25 l (0.26 US. qt, 0.22 Imp. qt.)
Ignition system
Ignition timing 30° B.T.D.C.
Spark plug NGK: CR5HSB
Spark plug gap 0.6-0.7 mm (0.024-0.028 in)
Spark plug tightening torque 12 Nm; 1.2 kg·m; 8.6 ft·lb
Primary ignition coil resistance 0.98-1.20 kΩ
Secondary ignition coil resistance 8-10 kΩ
Ignition coil air gap 0.3-0.5 mm (0.012-0.020 in)
Main jet #55
Float height 12 mm (0.47 in)
Pilot screw opening 1-1/8 turns out
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1 Comment

  1. Please …What size are the 4 bolts around the shaft that attaches a transmission on a Honda GXH 50? I have searched my manual and websites with no luck. Thx

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