Honda GX31 Specifications
| Engine Model: Honda GX31 |
| Engine Type: 4-cycle single-cylinder OHV air-cooled gasoline |
| Total Displacement: 1.9 cu.in (31 cc) |
| Rated Engine Power: 1.5 Hp (1.12 kW) at 7000 rpm |
| Carburetor Type: Diaphragm |
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Engine Model ................. Honda GX31
Engine Type ................. 4-cycle 1-cylinder OHV air-cooled gasoline
Number of Cylinders ................. Single
Displacement, cu.in (cc) ................. 1.9 (31.0)
Cylinder Bore, in (mm) ................. 1.54 (39.0)
Piston Stroke, in (mm) ................. 1.02 (26.0)
Rated Engine Power, hp (kW) ................. 1.5 (1.12)
Rated Engine Speed, rpm ................. 7000
Idle Speed, rpm ................. 3100±200
Maximum Torque, Nm (ft-lbs) ................. 1.64 (1.2)
Torque Speed, rpm ................. 6500
Compression Ratio ................. 8.0:1
Lubrication System ................. Pumping spray
Cooling System ................. Forced air
Ignition System ................. Transistorized magneto
Starting System ................. Recoil starter
Electrical System Rating, Volts .................. 12
Fuel System Type ................. Carburetor
Carburetor Type ................. Diaphragm
Fuel Consumption, g/HPh ................. 340
Fuel Type ................. Gasoline (86 or higher)
Fuel Tank Capacity, qts (L) ................. 0.68 (0.65)
Overall Length, in (mm) ................. 8.3 (210)
Overall Width, in (mm) ................. 9.9 (250)
Overall Height, in (mm) ................. 9.9 (250)
Net Weight, lbs (kg) ................. 7.5 (3.4)
Cylinder Compression, psi (kPa) ................. 41-84 (285-580)
Cylinder Bore Inside Diameter (Std), in (mm) ................. 1.538 (39.00)
Cylinder Bore Inside Diameter (Wear Limit), in (mm) ................. 1.542 (39.10)
Piston Skirt Outside Diameter (Std), in (mm) ................. 1.535 (38.98)
Top Ring Width, in (mm) .................. 0.04 (0.98)
Middle Ring Width, in (mm) .................. 0.04 (0.98)
Top Ring End Gap, in (mm) .................. 0.004-0.01 (0.10-0.25)
Middle Ring End Gap, in (mm) .................. 0.004-0.01 (0.10-0.25)
Oil Ring End Gap, in (mm) .................. 0.006-0.002 (0.015-0.05)
Cylinder Head (Max Out of Flatness), in (mm) ................. 0.004 (0.10)
Intake Valve Clearance, in (mm) ................. 0.004-0.006 (0.10-0.14)
Exhaust Valve Clearance, in (mm) ................. 0.005-0.007 (0.13-0.17)
Intake Valve Stem Outside Diameter, in (mm) ................. 0.1569 (3.985)
Exhaust Valve Stem Outside Diameter, in (mm) ................. 0.1555 (3.950)
Intake Valve Guide Inside Diameter, in (mm) ................. 0.1575 (4.00)
Exhaust Valve Guide Inside Diameter, in (mm) ................. 0.1575 (4.00)
Camshaft Journal Outside Diameter, in (mm) ................. 0.20 (5.02)
Intake Cam Height, in (mm) ................. 0.897 (22.8)
Exhaust Cam Height, in (mm) ................. 0.897 (22.8)
Engine Oil Type (Summer) ................. SAE 10W-30
Engine Oil Type (Winter) ................. SAE 10W
API Service Classifications ................. SG or SF
Oil Capacity, qts (L) ................. 0.11 (0.10)
Spark Plug Type ................. NGK C5HSB, CR5HSB, Denso U16FS-UB, U16FSR-UB
Spark Plug Gap, in (mm) ................. 0.0236-0.0276 (0.60-0.70)
Ignition Coil Air Gap, in (mm) ................. 0.014-0.020 (0.35-0.50)
Ignition Timing, deg ................. 27 BTDC
Cylinder Head Bolt, Nm (ft-lb) ................. 4 (2.9)
Crankcase Bolt, Nm (ft-lb) ................. 7 (5.1)
Camshaft Cover Bolt, Nm (ft-lb) ................. 3 (2.2)
Flywheel Nut, Nm (ft-lb) ................. 15 (11)
Clutch Bolt, Nm (ft-lb) ................. 15 (11)
Recoil Starter Pulley, Nm (ft-lbs) ................. 8 (5.7)
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