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Honda GXH50 Engine

The Honda GXH50 is a 4-stroke OHV single cylinder horizontal shaft air-cooled gasoline engine from GXH-series. A 2.99 cu. in (49.1 cc) engine has a cylinder bore of 1.66" (42 mm), piston stroke of 1.42" (36 mm), and rated power of 2.1 Hp (1.6 kW) at 4500 rpm. The compression ratio rating is 8:1. The Honda GXH50 engine is equipped with a splash type lubrication system, float type carburetor, forced-air cooling system, and transistorized magneto ignition system. The operating weight is 12 lbs (5.5 kg).

General Technical Data

Engine Specifications

Engine Model ................. Honda GXH50
Engine Type ................. 4-cycle 1-cylinder OHV air-cooled gasoline
Number of Cylinders ................. Single
Displacement, cu.in (cc) ................. 2.99 (49.1)
Cylinder Bore, in (mm) ................. 1.66 (42.0)
Piston Stroke, in (mm) ................. 1.42 (36.0)
Rated Engine Power, hp (kW) ................. 2.1 (1.6)
Rated Engine Speed, rpm ................. 4500
Idle Speed, rpm ................. 2500±100
Maximum Torque, Nm (ft-lbs) ................. 2.7 (2.0)
Torque Speed, rpm ................. 4500
Compression Ratio ................. 8.0:1
Lubrication System ................. Splash type
Cooling System ................. Forced air
Ignition System ................. Transistorized magneto
Starting System ................. Recoil starter
Electrical System Rating, Volts .................. 12

Fuel System

Fuel System Type ................. Carburetor
Carburetor Type ................. Float
Fuel Consumption, g/HPh ................. 240
Fuel Type ................. Gasoline (86 or higher)
Fuel Tank Capacity, qts (L) ................. 1.3 (1.2)

Dimensions and Weight

Overall Length, in (mm) ................. 8.9 (225)
Overall Width, in (mm) ................. 10.8 (275)
Overall Height, in (mm) ................. 14.0 (355)
Net Weight, lbs (kg) ................. 12.1 (5.5)

Maintenance Data

Engine Oil

Engine Oil Type (Summer) ................. SAE 10W-30
Engine Oil Type (Winter) ................. SAE 10W
API Service Classifications ................. SG or SF
Oil Capacity, qts (L) ................. 0.26 (0.25)

Carburetor Adjustment

Carb Main Jet ................. #55
Float Height, in (mm) ................. 0.47 (12.0)
Pilot Screw Opening ................. 1-1/8 turns out
Idling Speed, rpm ................. 2500±200

Ignition System

Spark Plug Type ................. NGK CR5HSB, Denso U16FSR-UB
Spark Plug Gap, in (mm) ................. 0.0236-0.0276 (0.60-0.70)
Ignition Coil Air Gap, in (mm) ................. 0.012-0.020 (0.3-0.5)
Ignition Timing, deg ................. 30 BTDC

Service Specifications

Cylinder Block

Cylinder Compression, psi (kPa) ................. 61 (420)
Cylinder Bore Inside Diameter (Std), in (mm) ................. 1.6445 (41.80)
Cylinder Bore Inside Diameter (Wear Limit), in (mm) ................. 1.6463 (41.815)
Connecting Rod Small End I.D, in (mm) .................. 0.3939-0.3944 (10.006-10.007)
Connecting Rod Big End I.D, in (mm) .................. 0.5906-0.5910 (15.000-15.011)
Crankpin Outside Diameter (Std), in (mm) .................. 0.5895-0.5899 (14.973-14.984)
Piston Skirt Outside Diameter (Std), in (mm) ................. 1.6453 (41.79)
Piston Skirt Outside Diameter (Wear Limit), in (mm) ................. 1.6445 (41.77)
Top Ring Width, in (mm) .................. 0.030-0.031 (0.77-0.79)
Middle Ring Width, in (mm) .................. 0.038-0.039 (0.97-0.99)
Top Ring Side Clearance, in (mm) .................. 0.0006-0.0020 (0.015-0.050)
Middle Ring Side Clearance, in (mm) .................. 0.0006-0.0020 (0.015-0.050)
Top Ring End Gap, in (mm) .................. 0.006-0.012 (0.15-0.30)
Middle Ring End Gap, in (mm) .................. 0.006-0.012(0.15-0.30)

Cylinder Head and Valves

Cylinder Head (Max Out of Flatness), in (mm) ................. 0.004 (0.10)
Intake Valve Clearance, in (mm) ................. 0.002-0.004 (0.06-0.10)
Exhaust Valve Clearance, in (mm) ................. 0.003-0.005 (0.09-0.13)
Intake Valve Stem Outside Diameter, in (mm) ................. 0.1563-0.1569 (3.970-3.985)
Exhaust Valve Stem Outside Diameter, in (mm) ................. 0.1549-0.1555 (3.935-3.950)
Intake Valve Spring Free Length, in (mm) ................. 0.93 (23.7)
Exhaust Valve Spring Free Length, in (mm) ................. 0.93 (23.7)
Intake Cam Height, in (mm) ................. 1.101 (27.97)
Exhaust Cam Height, in (mm) ................. 1.101 (27.97)

Tightening Torque Specs

Connecting Rod Bolt, Nm (ft-lb) ................. 6 (4.3)
Crankcase Cover Bolt, Nm (ft-lb) ................. 7.5 (5.4)
Flywheel Nut, Nm (ft-lb) ................. 22 (16)
Oil Case Bolt, Nm (ft-lb) ................. 7.5 (5.4)
Ignition Coil Bolt, Nm (ft-lb) ................. 6 (4.3)
Carburetor Drain Screw, Nm (ft-lb) ................. 1.5 (1.1)
Carburetor Drain Bolt, Nm (ft-lb) ................. 4.5 (3.3)
Spark Plug, Nm (ft-lb) ................. 12 (8.7)

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