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
Type4-stroke, OHV, single cylinder
Displacement49 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
CarburetorFloat type
Cooling systemForced-air
Ignition systemTransistorized magneto ignition
Lubricating systemSplash
Starting systemRecoil starter
Stoping systemIgnition primary circuit ground
Fuel usedUnleaded gasoline (octane number 86 or higher)
Fuel tank capacity1.2 L (0.32 US gal, 0.26 Imp gal)
Fuel consumption240 g/HPh
PTO shaft rotationCounterclockwise (from PTO shaft side)

Cylinder Block and Head

Cylinder block
Compression ratio:8.0:1
Bore x Stroke41.8 mm X 36 mm (1.65 x 1.42 in)
Sleeve internal diameter41.800-41.815 mm (1.6445-1.6463 in)
Piston skirt outer diameter41.770-41.790 mm (1.6445-1.6453 in)
Ring side clearanceTop/second0.015-0.050 mm (0.0006-0.0020 in)
Ring end gapTop0.15-0.30 mm (0.0059-0.0118 in)
Second0.15-0.30 mm (0.0059-0.0118 in)
Ring widthTop0.77-0.79 mm (0.030-0.031 in)
Second0.97-0.99 mm (0.038-0.039 in)
Connecting rod small end ID10.006-10.007 mm (0.3939-0.3944 in)
Connecting rod big end ID15.000-15.011 mm (0.5906-0.5910 in)
Crankpin outer diameter14.973-14.984 mm (0.5895-0.5899 in)
Cylinder Head
Warpage (limit)0.10 mm (0.004 in)
Valve Arrangement:OHV
Stem outer diameter (standard):INTAKE3.970-3.985 mm (0.1563-0.1569 in)
EXHAUST3.935-3.950 mm (0.1549-0.1555 in)
Spring free length23.7.0 mm (0.93 in)
Cam height27.972 mm (1.1013 in)

Tightening torque specs

Tightening torque specs
Spark plug12 Nm; 1.2 kg·m; 8.6 ft·lb
Connecting rod bolt6 Nm; 0.6 kg·m; 4.3 ft·lb
Crankcase cover bolt7.5 Nm; 0.75 kg·m; 5.4 ft·lb
Oil case bolt7.5 Nm; 0.75 kg·m; 5.4 ft·lb
Flywheel nut22 Nm; 2.2 kg·m; 16 ft·lb
Igniton coil bolt6 Nm; 0.6 kg·m; 5 ft·lb
Carburetor drain screw1.2 Nm; 0.12 kg·m; 0.9 ft·lb
Carburetor drain bolt4.5 Nm; 0.45 kg·m; 3.3 ft·lb
4 mm bolts, nuts3.5 Nm; 0.35 kg·m; 2.5 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

Service Information

Maximum speed7,800 ± 150 rpm
Idle speed2,500 ± 200 rpm
Cylinder compression4.3 kg/cm2 (61 psi) at 1000 rpm
Valve clearance
Intake valve0.06-0.10 mm (0.0024-0.0039 in)
Exhaust valve0.09-0.13 mm (0.0035-0.0051 in)
Oil system
Oil typeHonda 4-stroke or an equivalent (SE or SF)
Recommended oilSAE 10W-30
Oil capacity0.25 l (0.26 US. qt, 0.22 Imp. qt.)
Ignition system
Ignition timing30° B.T.D.C.
Spark plugNGK: CR5HSB
Spark plug gap0.6-0.7 mm (0.024-0.028 in)
Spark plug tightening torque12 Nm; 1.2 kg·m; 8.6 ft·lb
Primary ignition coil resistance0.98-1.20 kΩ
Secondary ignition coil resistance8-10 kΩ
Ignition coil air gap0.3-0.5 mm (0.012-0.020 in)
Main jet#55
Float height12 mm (0.47 in)
Pilot screw opening1-1/8 turns out
Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

ATTENTION! Dear visitors, this site is not a trading platform, an official dealer or a spare parts supplier, so we do not have any price lists or spare parts catalogs. We are an information portal and provide the technical specifications of gasoline and diesel engines.

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.

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

Leave a Reply

Your email address will not be published.