The Rato R420 is a 420 cc (25.63 cu-in) single-cylinder air-cooled 4-stroke internal combustion general-purpose gasoline engine with horizontal shaft manufactured by Chongqing RATO Holding (Group) CO., LTD.
The Rato R420 engine has an (OHV) overhead-valve design; flat suction valve carburetor; recoil starter or electric starter, transistorized magneto ignition (TCI) system and centrifugal mechanical governor system.
The R420 motor has a 90.0 mm (3.54 in) cylinder bore and 66.0 mm (2.60 in) piston stroke with a compression ratio of 8.5:1. It produced 15.0 HP of horsepower at 3,600 rpm and 26.5 N·m (2.7 kg·m, 19.54 ft·lb) at 2,500 rpm of torque.
General information
| Engine Specifications | |
| Model | R420 |
| Type | 4-stroke, OHV, single cylinder |
| Displacement | 420 cm 3 (25.63 cu-in) |
| Max. horsepower | 15.0 HP at 3,600 rpm |
| Max. torque (crank PTO) | 26.5 N·m (2.7 kg·m, 19.54 ft·lb) at 2,500 rpm |
| Carburetor | Flat suction valve carburetor |
| Cooling system | Forced-air |
| Ignition system | Transistorized magneto ignition (TCI) |
| Lubricating system | Splash |
| Starting system | Recoil / electric starter |
| Stoping system | Ignition primary circuit ground |
| Fuel used | Unleaded gasoline (octane number 86 or higher) |
| PTO shaft rotation | Counterclockwise (from PTO shaft side) |
Cylinder Block and Head
The Rato R420 engine has cast-iron cylinder liner, dual ball bearings and steel forged and hardened crankshaft.
| Cylinder block | ||
| Compression ratio: | 8.5:1 | |
| Bore x Stroke | 90 X 66 mm (3.54 x 2.60 in) | |
| Sleeve internal diameter | 90.000-90.015 mm (3.5433-3.5439 in) | |
| Piston skirt outer diameter | 89.960-89.970 mm (3.5417-3.5421 in) | |
| Number of piston rings (compression / oil): | 2 / 1 | |
| Ring side clearance | Top/Second | 0.020-0.060 mm (0.0008-0.0023 in) |
| Ring end gap | Top/Second | 0.20-0.40 mm (0.008-0.016 in) |
| Oil | 0.20-0.70 mm (0.008-0.027 in) | |
| Connecting rod small end ID | 20.011 mm (0.7878 in) | |
| Connecting rod big end ID | 36.025 mm (1.4183 in) | |
| Crankshaft crank pin outer diameter | 35.985 mm (1.4167 in) | |
| Cylinder Head | ||
| Warpage (limit) | 0.10 mm (0.004 in) | |
| Valve Arrangement: | OHV | |
| Valves: | 2 | |
| Stem outer diameter (standard): | INTAKE | 6.580 mm (0.2590 in) |
| EXHAUST | 6.560 mm (0.2583 in) | |
| Cam height: | INTAKE | 6.59 mm (0.2595 in) |
| EXHAUST | 6.07 mm (0.2390 in) | |
| Valve spring free length: | 39.0 mm (1.5354 in) | |
| Camshaft journal diameter: | 15.984 mm (0.6293 in) | |
Tightening torque specs
| Tightening torque specs | |
| Connecting rod bolt | 15 Nm; 1.5 kg·m; 11 ft·lb |
| Oil dran plug | 22 Nm; 2.2 kg·m; 16 ft·lb |
| Crankcase cover | 28 Nm; 2.8 kg·m; 21 ft·lb |
| Flywheel subassembly | 95 Nm; 9.5 kg·m; 70 ft·lb |
| Cylinder head subassembly | 42 Nm; 4.2 kg·m; 31 ft·lb |
| Rocker shaft bolt | 24 Nm; 2.4 kg·m; 18 ft·lb |
| Cylinder head cover | 10 Nm; 1.0 kg·m; 7 ft·lb |
| Spark plug | 28 Nm; 2.8 kg·m; 21 ft·lb |
| Ignition coil | 10 Nm; 1.0 kg·m; 7 ft·lb |
Service Information
| Engine | |
| Maximum speed | 3750-3810 rpm |
| Cylinder compression | 12.2 kg/cm2 at 1400 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 | 4-stroke or an equivalent (SJ) |
| Recommended oil | SAE 10W-30, 15W-40 |
| Oil capacity | 1.1 L |
| Ignition system | |
| Spark plug | NGK: BPR6ES |
| Spark plug gap | 0.7-0.8 mm (0.028-0.031 in) |
| Primary ignition coil resistance | 0.6-0.9 Ω |
| Secondary ignition coil resistance | 5.6-6.9 kΩ |
| Ignition coil air gap | 0.4 ± 0.2 (0.016 ± 0.008) |
Author:
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