The Honda GX670U is a 670 cc, (41.0 cu·in) natural aspirated V-twin four-stroke air-cooled internal combustion small gasoline engine with a horizontal shaft, manufactured by Honda Motor Company for general-purpose applications.
A 77.0 mm (3.03 in) cylinder bore and 72.0 mm (2.83 in) piston stroke give the GX670U engine a total of 670 cc of displacement. The compression ratio rating is 8.3:1.
The Honda GX670 U/R engine produced 20.8 PS (15.3 kW; 20.5 HP) at 3,600 rpm of maximum output power and 46.0 N·m (4.7 kg·m, 33.9 ft·lb) at 2,500 rpm of peak torque.
The Honda GX670U features:
- OHV design
- Transistorized magneto ignition system
- Horizontal type carburetor with butterfly valve
- Centrifugal governor
- Forced lubrication system
- Forced air cooling system
- Electric starter
General information
Engine Specifications | |
Engine model | GX670 U/R |
Engine type | 4-stroke, OHV, V-twin |
Displacement | 670 cm3, (40.89 cu·in) |
Max. horsepower | 20.8 PS (15.3 kW; 20.5 HP) at 3,600 rpm |
Max. torque | 46.0 N·m (4.7 kg·m, 33.9 ft·lb) at 2,500 rpm |
Cooling system | Forced air |
Air cleaner | Dual-element type |
Lubricating system | Forced lubrication |
Ignition system | Transistorized magneto ignition |
Fuel system | Horizontal type carburetor with butterfly valve |
Fuel consumption | 7.4L (1.96 US gal, 1.63 Imp gal)/hr |
Fuel tank capacity | – |
Fuel used | Unleaded gasoline (octane number 86 or higher) |
Starting system | Electric starter |
Stoping system | Ignition primary circuit ground |
Governor | Centrifugal governor |
PTO shaft rotation | Counterclockwise (from PTO shaft side) |
Dimensions (L x W X H) | – |
Dry weight | 43.5 kg (95.9 lbs) |
Cylinder Block and Head
Cylinder block | |
Compression ratio: | 8.3:1 |
Cylinder bore: | 77.0 mm (3.03 in) |
Piston stroke: | 72.0 mm (2.83 in) |
Cylinder internal diameter (standard): | 77.000 mm (3.0315 in) |
Piston skirt outer diameter (standard): | 76.985 mm (3.0309 in) |
Number of piston rings (compression / oil): | 2/1 |
Crankshaft center distance: | 36 mm (1.415 in) |
Cylinder head | |
Valve arrangement: | OHV, gear driven |
Valves: | 2,(4 valves in total) |
Tightening torque specs
Tightening torque specs | |
Connecting rod bolt | 12 Nm; 1.2 kg·m; 9 ft·lb |
Cylinder head bolt | 34 Nm; 3.5 kg·m; 25 ft·lb |
Socket bolt | 27 Nm; 2.7 kg·m; 20 ft·lb |
Flywheel nut | 196 Nm; 20.0 kg·m; 145 ft·lb |
Pivot bolt | 24 Nm; 2.4 kg·m; 17 ft·lb |
Pivot adjusting nut | 10 Nm; 1.0 kg·m; 7 ft·lb |
Cylinder head cover bolt | 9 Nm; 0.9 kg·m; 6.5 ft·lb |
Oil level switch joint nut | 10 Nm; 1.0 kg·m; 7 ft·lb |
Oil drain bolt | 39 Nm; 4.0 kg·m; 29 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) | 22 Nm; 2.2 kg·m; 16 ft·lb |
Bolt, nut (10 mm) | 34 Nm; 3.5 kg·m; 25 ft·lb |
Bolt, nut (12 mm) | 54 Nm; 5.5 kg·m; 40 ft·lb |
Service Data
Engine | |
Maximum speed: | 3,850±150 rpm rpm |
Idle speed: | 1,450±150 rpm rpm |
Cylinder compression: | 6.0-8.0 kg/cm2 (85-114 psi) at 500 rpm |
Valve clearance | |
Intake valve clearance (COLD): | 0.13-0.17 mm (0.0051-0.0067 in) |
Exhaust valve clearance (COLD): | 0.18-0.22 mm (0.0071-0.0087 in) |
Oil system | |
Lubrication system: | Forced lubrication |
Oil type: | Honda 4-stroke or an equivalent (SJ or later) |
Recommended oil: | SAE 10W-30 |
Oil capacity: |
With oil filter replacement:: 1.4 L (1.48 US. qt, 1.23 Imp. qt.) Without oil filter replacement:: 1.1 L (1.16 US. qt, 0.97 Imp. qt.) |
Fuel system | |
Type: | Horizontal type carburetor with butterfly valve |
Ignition system | |
Type: | Transistorized magneto ignition |
Spark plug: | NGK ZGR5A DENSO J16CR-U |
Spark plug gap: | 0.7-0.8 mm (0.0276-0.0315 in) |
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