Honda GXV120

Honda GXV120 engineThe Honda GXV120 is a 118 cc (7.2 cu-in) single-cylinder air-cooled four-stroke internal combustion small gasoline engine with vertical shaft manufactured by Honda Motor Company for general-purpose applications, such as lawn mowers, commercial lawn and garden equipment, forestry equipment, construction and industrial equipment, agricultural equipment.

The Honda GXV120 engine has an OHV (overhead valve) design; horizontal type carburetor with butterfly valve; centrifugal mechanical governor; heavy-duty recoil or electric starter and transistorized magneto ignition system.

The cylinder bore is 60.0 mm (2.4 in) and the piston stroke is 42.0 mm (1.7 in), compression ratio rating is 8.0:1 or 8.7:1. The engine produced 4.0 HP (2.9 kW) of horsepower at 3,600 rpm and 8.0 Nm (0.82 kg·m, 5.92 ft·lb) of torque at 2,700 rpm.

General information

Engine Specifications
ModelGXV120
Type4-stroke, OHV, single cylinder
Displacement118 cm 3 (7.2 cu-in)
Max. horsepower4.0 HP (2.9 kW) at 3,600 rpm
Max. torque (crank PTO)8.0 Nm (0.82 kg·m, 5.92 ft·lb) at 2,700 rpm
CarburetorHorizontal type, butterfly valve
Cooling systemForced-air
Ignition systemTransistorized magneto ignition
Lubricating systemForced splash
Starting systemRecoil starter / Self starter
Stoping systemIgnition primary circuit ground
Fuel usedUnleaded gasoline (octane number 86 or higher)
Fuel tank capacity1.0 L (0.26 US qt)
Fuel consumption250 g/HPh
PTO shaft rotationCounterclockwise (from PTO shaft side)

Cylinder Block and Head

The Honda GXV120 motor has cast iron cylinder sleeve, ball bearing supported forged steel crankshaft. The piston has two compression rings and one oil ring. Precision camshaft design offers precise valve timing and optimal valve overlap for better fuel efficiency.

Cylinder block
Compression ratio: 8.7:1 for engine with S/N: 100001-1219523
8.0:1 for engine with S/N: from 1219524
Bore x Stroke60 X 42 mm (2.4 x 1.7 in)
Sleeve internal diameter60.000 mm (2.3622 in)
Piston skirt outer diameter59.985 mm (2.3616 in)
Number of piston rings (compression / oil):2 / 1
Ring side clearanceTop0.015-0.045 mm (0.0006-0.0018 in)
Second0.015-0.045 mm (0.0006-0.0018 in)
Ring end gapTop/Second0.20-0.40 mm (0.008-0.016 in)
Oil0.15-0.35 mm (0.006-0.014 in)
Ring widthTop/Second1.5 mm (0.06 in)
Oil2.5 mm (0.10 in)
Connecting rod small end ID13.005 mm (0.5120 in)
Connecting rod big end ID26.02 mm (1.024 in)
Piston pin outer diameter13.0 mm (0.5118 in)
Crankshaft crank pin outer diameter25.98 mm (1.023 in)
Cylinder Head
Warpage (limit)0.10 mm (0.004 in)
Valve Arrangement:OHV
Valves:2
Stem outer diameter (standard):INTAKE5.480 mm (0.216 in)
EXHAUST5.440 mm (0.214 in)
Valve spring free length:34.0 mm (1.339 in)
Camshaft outer diameter:13.984 mm (0.5506 in)
Cam height:INTAKE27.70 mm (1.09 in)
EXHAUST27.75 mm (1.093 in)

Tightening torque specs

Tightening torque specs
Connecting rod lower cap12 Nm; 1.2 kg·m; 9 ft·lb
Cylinder head bolt24 Nm; 2.4 kg·m; 17 ft·lb
Flywheel nut75 Nm; 7.5 kg·m; 54 ft·lb
Pivot adjusting nut10 Nm; 1.0 kg·m; 7 ft·lb
Pivot bolt24 Nm; 2.4 kg·m; 17 ft·lb
Oil filter extension10 Nm; 1.0 kg·m; 7 ft·lb
Oil drain bolt18 Nm; 1.8 kg·m; 13 ft·lb
Oil pan24 Nm; 2.4 kg·m; 17 ft·lb
Standard torque values
Bolt, nut (5 mm)5.5 Nm; 0.55 kg·m; 4.0 ft·lb
Bolt, nut (6 mm)10 Nm; 1.0 kg·m; 7 ft·lb
Bolt, nut (8 mm)24 Nm; 2.4 kg·m; 17 ft·lb
Bolt, nut (10 mm)37.5 Nm; 3.75 kg·m; 27 ft·lb
Bolt, nut (12 mm)55 Nm; 5.5 kg·m; 40 ft·lb

Service Information

Engine
Maximum speed3,100 ± 100 rpm
Idle speed2,000 ± 150 rpm
Cylinder compression3.0-7.0 kg/cm2 (44-100 psi) at 600 rpm
Valve clearance
Intake valve clearance0.15±0.02 mm (0.006±0.001 in)
Exhaust valve clearance0.20±0.02 mm (0.008±0.001 in)
Oil system
Oil typeHonda 4-stroke or an equivalent (SE or SF)
Recommended oilSAE 10W-30
Oil capacity0.6 L (0.63 US. qt, 0.53 Imp. qt.)
Carburetor
Main jet#65
Float height12.2-15.2 mm (0.48-0.60 in)
Pilot screw opening3 turns out
Ignition system
Ignition timing25° B.T.D.C.
Spark plugNGK: BP5ES, BPR5ES
NIPPONDENSO: W16EP-U, W16EPR-U
Spark plug gap0.7-0.8 mm (0.028-0.031 in)
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