Honda GX120 Specifications
| Engine Model: Honda GX120 |
| Engine Type: 4-cycle single-cylinder OHV air-cooled gasoline |
| Total Displacement: 7.2 cu.in (118 cc) |
| Rated Engine Power: 3.5 Hp (2.6 kW) at 3600 rpm |
| Carburetor Type: Horizonal with butterfly valve |
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Engine Model .............. Honda GX120
Engine Type .............. 4-cycle overhead valve 1-cylinder air-cooled small gasoline engine
Number of Cylinders .............. Single
Displacement, cu.in (cc) .............. 7.2 (118)
Cylinder Bore, in (mm) .............. 2.36 (60.0)
Piston Stroke, in (mm) .............. 1.65 (42.0)
Rated Engine Power, hp (kW) .............. 3.5 (2.6)
Rated Engine Speed, rpm .............. 3600
Maximum Torque, Nm (ft-lbs) .............. 7.3 (5.4)
Torque Speed, rpm .............. 2500
Compression Ratio .............. 8.5:1
Valve Arrangement .............. OHV
Lubrication System .............. Forced splash type
Air Cleaner .............. Dual type, semi dry type
Cooling System .............. Forced air
Ignition System .............. C.D.I. type magneto ignition
Breather System .............. Reed valve type
Starting System .............. Recoil starter
Fuel System Type .............. Carburetor
Carburetor Type .............. Horizonal with butterfly valve
Governor Type .............. Mechanical centrifugal
Fuel Tank Capacity, qts (L) .............. 2.1 (2.0)
Fuel Type .............. Gasoline (86 or higher)
Overall Length, in (mm) .............. 13.1 (332)
Overall Width, in (mm) .............. 13.6 (346)
Overall Height, in (mm) .............. 13.0 (329)
Dry Weight, lbs (kg) .............. 30.9 (14.0)
Cylinder Bore Inside Diameter (Std), in (mm) .............. 2.3622-2.3628 (60.000-60.015)
Cylinder Bore Inside Diameter (Wear Limit), in (mm) .............. 2.3687 (60.165)
Connecting Rod Small End Inside Diameter (Std), in (mm) .............. 0.5120-0.5126 (13.005-13.020)
Connecting Rod Small End Inside Diameter (Wear Limit), in (mm) .............. 0.515 (13.07)
Connecting Rod Big End Inside Diameter (Std), in (mm) .............. 1.0244-1.0249 (26.020-26.033)
Connecting Rod Big End Inside Diameter (Wear Limit), in (mm) .............. 1.026 (26.066)
Connecting Rod Big End Oil Clearance, in (mm) .............. 0.0016-0.0025 (0.040-0.063)
Crank Pin Outside Diameter (Std), in (mm) .............. 1.0224-1.0228 (25.970-25.980)
Crank Pin Outside Diameter (Wear Limit), in (mm) .............. 1.020 (25.92)
Number of Valves .............. 2
Cylinder Head (Max Out of Flatness), in (mm) .............. 0.004 (0.10)
Intake Valve Clearance, in (mm) .............. 0.005-0.007 (0.13-0.17)
Exhaust Valve Clearance, in (mm) .............. 0.007-0.009 (0.18-0.22)
Intake Valve Stem Outside Diameter (Std), in (mm) .............. 0.2153-0.2157 (5.468-5.480)
Intake Valve Stem Outside Diameter (Wear Limit), in (mm) .............. 0.2094 (5.318)
Exhaust Valve Stem Outside Diameter (Std), in (mm) .............. 0.2136-0.2142 (5.425-5.440)
Exhaust Valve Stem Outside Diameter (Wear Limit), in (mm) .............. 0.2077 (5.275)
Intake Valve Guide Inside Diameter, in (mm) .............. 0.2165-0.2170 (5.500-5.512)
Exhaust Valve Guide Inside Diameter, in (mm) .............. 0.2165-0.2170 (5.500-5.512)
Intake Valve Guide To Stem Clearance, in (mm) .............. 0.0008-0.0017 (0.020-0.044)
Exhaust Valve Guide To Stem Clearance, in (mm) .............. 0.0024-0.0034 (0.060-0.087)
Valve Seat Width (Intake/Exhaust), in (mm) .............. 0.03-0.04 (0.70-0.90)
Valve Spring Free Length, in (mm) .............. 1.20 (30.50)
Cam Height (Intake), in (mm) .............. 1.0827-1.0984 (27.500-27.900)
Cam Height (Exhaust), in (mm) .............. 1.0845-1.1003 (27.547-27.947)
Camshaft Outside Diameter (Std), in (mm) .............. 0.5498-0.5506 (13.966-13.984)
Camshaft Outside Diameter (Wear Limit), in (mm) .............. 0.5479 (13.916)
Piston Pin Bore Inside Diameter (Std), in (mm) .............. 0.5119-0.5121 (13.002-13.008)
Piston Pin Bore Inside Diameter (Wear Limit), in (mm) .............. 0.5137 (13.048)
Piston Skirt Outside Diameter, in (mm) .............. 2.3608-2.3616 (59.965-59.985)
Piston to Cylinder Bore Clearance, in (mm) .............. 0.0006-0.0020 (0.015-0.050)
Piston Pin Outside Diameter (Std), in (mm) .............. 0.5116-0.5118 (12.994-13.000)
Piston Pin Outside Diameter (Wear Limit), in (mm) .............. 0.5100 (12.954)
Top Ring Width, in (mm) .............. 0.0374-0.0382 (0.950-0.970)
Second Ring Width, in (mm) .............. 0.0370-0.0378 (0.940-0.960)
Top Ring Groove Side Clearance, in (mm) .............. 0.0014-0.0028 (0.035-0.070)
Second Ring Groove Side Clearance, in (mm) .............. 0.0018-0.0032 (0.045-0.080)
Top Ring End Gap, in (mm) .............. 0.008-0.014 (0.20-0.35)
Second Ring End Gap, in (mm) .............. 0.014-0.020 (0.35-0.50)
Oil Ring End Gap, in (mm) .............. 0.01-0.03 (0.20-0.70)
Ring End Gap (Wear Limit), in (mm) .............. 0.04 (1.00)
Cylinder Bore Inside Diameter (Max), in (mm) .............. 2.3687 (60.165)
Cylinder Compression, psi (kPa) .............. 71-100 (490-690)
Cylinder Head (Max Out of Flatness), in (mm) .............. 0.004 (0.10)
Intake Valve Clearance, in (mm) .............. 0.006 (0.15)
Exhaust Valve Clearance, in (mm) .............. 0.008 (0.20)
Engine Oil Type (Summer) .............. SAE 10W-30
Engine Oil Type (Winter) .............. SAE 5W-30
API Service Classifications .............. SJ or higher
Oil Capacity, qts (L) .............. 0.59 (0.56)
Air Filter Element Part Number .............. 17211-ZE1-000
Spark Plug Type .............. NGK BPR6ES or Denso W20EPR-U
Spark Plug Gap, in (mm) .............. 0.028-0.032 (0.70-0.80)
Module Air Gap, in (mm) .............. 0.008-0.024 (0.20-0.60)
Ignition Timing, deg .............. 20 BTDC
Main Jet .............. #60
Idle Fuel (BE99A) .............. 1-5/8 turns out
Idle Fuel (BE61M) .............. 2-1/8 turns out
Float Height, in (mm) .............. 0.54 (13.7)
Low Idle Speed, rpm .............. 1400±150
High Idle Speed, rpm .............. 3900±100
Check Engine Oil Level .............. Every 10 hours
Clean Air Filter Element .............. Every 50 hours
Change Engine Oil .............. Every 100 hours
Check and Adjust Spark Plug .............. Every 100 hours
Clean Fuel Strainer .............. Every 100 hours
Check and Adjust Idle Speed .............. Every 300 hours
Check Carburetor Adjustments .............. Every 300 hours
Replace Spark Plug .............. Every 300 hours
Replace Air Filter Element .............. Every 300 hours
Check and Adjust Valve Clearance .............. Every 300 hours
Clean Combustion Chamber .............. Every 500 hours
Clean Fuel Line .............. Every 500 hours
Crankcase Cover (M6x1.0) .............. 12 Nm (9 ft-lb)
Cylinder Head Cover Bolt (M8x1.25) .............. 24 Nm (18 ft-lb)
Oil Drain Plug Bolt (M10x1.25) .............. 18 Nm (13 ft-lb)
Connecting Rod Bolt (M7x1.0) .............. 12 Nm (9 ft-lb)
Rocker Arm Pivot Bolt (M8x1.25) .............. 24 Nm (18 ft-lb)
Flywheel Nut (M14x1.5) .............. 75 Nm (55 ft-lb)
Air Cleaner Case Bolt (M6x1.0) .............. 9 Nm (6.6 ft-lb)
Muffler Bolt (M8x1.25) .............. 24 Nm (18 ft-lb)
Recoil Starter Screw (M6x1.0) .............. 5.4 Nm (4 ft-lb)
Oil Level Switch Bolt (M10x1.25) .............. 10 Nm (7 ft-lb)
Fuel Strainer Cup (M24x1.0) .............. 3.9 Nm (2.9 ft-lb)
Spark Plug (M14x1.25) .............. 20 Nm (14 ft-lb)
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