The Honda GX620 U1/R1 is a 614 cc, (37.5 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.
Cylinder bore and piston stroke are 77.0 mm (3.03 in) and 66.0 mm (2.6 in), respectively. The compression ratio rating is 8.3:1.
The Honda GX620 U1/R1 engine produced 18.4 PS (13.5 kW; 18.1 HP) at 3,600 rpm of maximum output power and 40.6 N·m (4.1 kg·m, 29.9 ft·lb) at 2,500 rpm of peak torque.
The Honda GX620 U1/R1 features:
- Overhead valve (OHV) design
- Transistorized magneto ignition system
- Horizontal type carburetor with butterfly valve
- Centrifugal governor
- Forced lubrication system
- Forced air cooling system
- Recoil or electric starter
General information
| Engine Specifications | |
| Engine model | GX620 U1/R1 |
| Engine type | 4-stroke, OHV, V-twin |
| Displacement | 614 cm3, (37.47 cu·in) |
| Max. horsepower | 18.4 PS (13.5 kW; 18.0 HP) at 3,600 rpm |
| Max. torque | 40.6 N·m (4.1 kg·m, 29.9 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 | 313 g/kWh |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Starting system | Recoil or 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) | 388 x 457 x 452 mm (15.3 x 18 x 17.8 in) |
| Dry weight | 42.0 kg (92.6 lbs) |
Cylinder Block and Head
| Cylinder block | |
| Compression ratio: | 8.3:1 |
| Cylinder bore: | 77.0 mm (3.03 in) |
| Piston stroke: | 66.0 mm (2.6 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 |
| Connecting rod small end diameter (standard): | 18.005 mm (0.7089 in) |
| Piston pin diameter: | 18.000 mm (0.7087 in) |
| Side clearance (Top): | 0.030-0.060 mm (0.0012-0.0024 in) |
| Side clearance (Second): | 0.030-0.060 mm (0.0012-0.0024 in) |
| Ring end gap (Top): | 0.20-0.40 mm (0.0079-0.0157 in) |
| Ring end gap (Second): | 0.20-0.40 mm (0.0079-0.0157 in) |
| Ring width (Top): | 1.990 mm (0.0783 in) |
| Ring width (Second): | 1.990 mm (0.0783 in) |
| Crankshaft main journal diameter: | 38.000 mm (1.4961 in) |
| Crankpin journal diameter: | 39.995 mm (1.5746 in) |
| Crankshaft center distance: | 33.0 mm (1.3 in) |
| Cylinder head | |
| Valve arrangement: | OHV, gear driven |
| Valves: | 2 ,(4 valves in total) |
| Valve steam diameter (INTAKE): | 6.590 mm (0.2594 in) |
| Valve steam diameter (EXHAUST): | 6.550 mm (0.2579 in) |
| Valve spring free length (INTAKE): | 39.0 mm (1.5354 in) |
| Valve spring free length (EXHAUST): | 39.0 mm (1.5354 in) |
| Camshaft lobe height (INTAKE): | 29.865 mm (1.1758 in) |
| Camshaft lobe height (EXHAUST): | 29.865 mm (1.1758 in) |
| Camshaft journal diameter : | 16.985 mm (0.6687 in) |
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 |
| Idle speed: | 1,400 ±150 rpm rpm |
| Cylinder compression: | 6.0-8.0 kg/cm2 (85-121 psi) at 600 rpm |
| Valve clearance | |
| Intake valve clearance): | 0.15±0.02 mm (0.006±0.001 in) |
| Exhaust valve clearance: | 0.20±0.02 mm (0.008±0.001 in) |
| Oil system | |
| Lubrication system: | Forced lubrication |
| Oil type: | Honda 4-stroke or an equivalent (SG or SF) |
| Recommended oil: | SAE 10W-30 or 10W-40 |
| Oil capacity: | 1.50 L (1.59 US. qt, 1.32 Imp. qt.) |
| Fuel system | |
| Type: | Horizontal type carburetor with butterfly valve |
| Ignition system | |
| Type: | Transistorized magneto ignition |
| Ignition timing: | B.T.D.C. 20° (Fixed) |
| Spark plug: | NGK: ZGR5A DENSO: J16CR-U |
| Spark plug gap: | 0.7-0.8 mm (0.0276-0.0315 in) |
| Spark plug torque: | 18 N·m (1.8 kg·m, 13.3 ft·lb) |
| Ignition coil air gap | 0.2-0.6 mm (0.0079-0.0236 in) |
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