| Engine Specifications | |
| Model | GX620 K1 |
| Type | 4-stroke, OHV, 90° V-twin |
| Displacement | 614 cm 3 (37.5 cu-in) |
| Max. horsepower | 20 HP (14.9 kW HP) at 3,600 rpm |
| Max. torque (crank PTO) | 44.1 N·m (4.50 kg·m, 32.5 ft·lb) at 2,500 rpm |
| Carburetor | Horizontal type, butterfly valve |
| Cooling system | Forced-air |
| Ignition system | Transistorized magneto ignition |
| Lubricating system | Forced lubrication |
| Starting system | Recoil starter or Recoil and electric starter |
| Stoping system | Ignition primary circuit ground |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| Fuel consumption | 230 g/HPh |
| PTO shaft rotation | Counterclockwise (from PTO shaft side) |
| QAF | VXE8 | SAE1 | |
| Length, mm (in) | 388 (15.3) | 408 (16.1) | 379 (15.0) |
| Width, mm (in) | 457 (18.0) | ||
| Height, mm (in) | 452 (17.8) | ||
| Dry weight, kg (lb) | 42.0 (92.6) | ||
| Operating weight, kg (lb) | 43.0 (94.8) | ||
| Cylinder block | ||
| Compression ratio: | 8.3:1 | |
| Bore x Stroke | 77 X 66 mm (3.0 x 2.6 in) | |
| Sleeve internal diameter | 77.00 mm (3.03 in) | |
| Piston skirt outer diameter | 76.985 mm (3.03 in) | |
| Ring side clearance | Top/Second | 0.030-0.060 mm (0.0006-0.0018 in) |
| Ring end gap | Top/Second | 0.20-0.40 mm (0.010-0.020 in) |
| Ring width | Top/Second | 1.990 mm (0.0783 in) |
| Connecting rod small end ID | 18.005 mm (0.7087 in) | |
| Piston pin outer diameter | 18.000 mm (0.7087 in) | |
| Crankpin diameter | 39.995 mm (1.5746 in) | |
| Crankshaft journal diameter | 38.000 mm (1.4961 in) | |
| Cylinder Head | ||
| Warpage (limit) | 0.10 mm (0.004 in) | |
| Valve Arrangement: | OHV | |
| Valves: | 4 (2 per cylinder) | |
| Stem outer diameter (standard): | INTAKE | 6.590 mm (0.2594 in) |
| EXHAUST | 6.550 mm (0.2579 in) | |
| Valve spring free length: | 39.0 mm (1.54 in) | |
| Valve lifter internal diameter: | 6.010 mm (0.2366 in) | |
| Valve lifter shaft outer diameter: | 6.000 mm (0.2362 in) | |
| Camshaft journal diameter: | 16.985 mm (0.6687 in) | |
| Cam height: | INTAKE | 29.865 mm (1.1758 in) |
| EXHAUST | 29.865 mm (1.1758 in) | |
| 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 |
| Engine | |
| Maximum speed | 3,850 ± 100 rpm |
| Idle speed | 1,400 ± 150 rpm |
| Cylinder compression | 6.0-8.0 kg/cm2 (85-114 psi) at 500 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 | |
| Oil type | Honda 4-stroke or an equivalent (SG or SF) |
| Recommended oil | SAE 10W-30 |
| Oil capacity | With oil filter: 1.80 L (1.90 US. qt, 1.58 Imp. qt.) Without oil filter: 1.50 L (1.59 US. qt, 1.32 Imp. qt.) |
| Oil change interval | Every 6 month or 100 Hrs. |
| Carburetor | |
| Main jet | #105 |
| Float height | 14.0 mm (0.55 in) |
| Pilot screw opening | 1-3/4 turns out |
| Ignition system | |
| Ignition timing | 20° B.T.D.C. |
| Spark plug |
NGK: ZGR5A DENSO: J16CR-U |
| Spark plug gap | 0.7-0.8 mm (0.028-0.031 in) |
| Primary ignition coil resistance | 0.8-1.0 Ω |
| Secondary ignition coil resistance | 5.9-7.1 kΩ |
| Ignition coil air gap | 0.4 ± 0.2 (0.016 ± 0.008) |
| Starter motor | |
| Brush length | 10.0 mm (0.43 in) |
