The Rato R300 is a 301 cc (18.4 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 R300 engine has an OHV design; flat suction valve carburetor; recoil starter or electric starter, transistorized magneto ignition (TCI) system and centrifugal mechanical governor system.
The R300 motor has an 80.0 mm (3.15 in) cylinder bore and 60.0 mm (2.36 in) piston stroke with a compression ratio of 8.5:1. It produced 12.0 HP of horsepower at 3,600 rpm and 18 N·m (1.83 kg·m, 13.27 ft·lb) of torque at 2,500 rpm.
General information
| Engine Specifications | |
| Model | R300 |
| Type | 4-stroke, OHV, single cylinder |
| Displacement | 301 cm 3 (18.4 cu-in) |
| Max. horsepower | 12.0 HP at 3,600 rpm |
| Max. torque (crank PTO) | 18 N·m (1.83 kg·m, 13.27 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 R300 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 | 80 X 60 mm (3.15 x 2.36 in) | |
| Sleeve internal diameter | 80.000-80.015 mm (3.1496-3.1501 in) | |
| Piston skirt outer diameter | 79.975-79.985 mm (3.1486-3.1490 in) | |
| Number of piston rings (compression / oil): | 2 / 1 | |
| Ring side clearance | Top/Second | 0.025-0.060 mm (0.0010-0.0023 in) |
| Ring end gap | Top | 0.20-0.40 mm (0.008-0.016 in) |
| Second | 0.30-0.50 mm (0.012-0.020 in) | |
| Oil | 0.20-0.70 mm (0.008-0.027 in) | |
| Connecting rod small end ID | 15.011-15.022 mm (0.5909-0.5914 in) | |
| Connecting rod big end ID | 33.025-33.039 mm (1.3001-1.3007 in) | |
| Crankshaft crank pin outer diameter | 32.975-32.985 mm (1.2982-1.2986 in) | |
| Cylinder Head | ||
| Warpage (limit) | 0.10 mm (0.004 in) | |
| Valve Arrangement: | OHV | |
| Valves: | 2 | |
| Stem outer diameter (standard): | INTAKE | 5.48 mm (0.216 in) |
| EXHAUST | 5.44 mm (0.214 in) | |
| Cam height: | INTAKE | 6.045 mm (0.2380 in) |
| EXHAUST | 5.766 mm (0.2270 in) | |
| Valve spring free length: | 38.5-39.5 mm (1.5157-1.5551 in) | |
| Camshaft journal diameter: | 16.166-16.184 mm (0.6364-0.6371 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 | 75 Nm; 7.5 kg·m; 55 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 | 3750-3850 rpm |
| Cylinder compression | 11.2 kg/cm2 at 1400 rpm |
| Valve clearance | |
| Intake valve clearance | 0.10-0.15 mm (0.004-0.006 in) |
| Exhaust valve clearance | 0.15-0.20 mm (0.006-0.008 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:
Thanks for the information. Do you has specs on the diameter and the length of the shaft? I am looking to put an equivalent engine in.