The Rato R225 is a 223 cc (13.6 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 R225 engine has an OHV design; flat suction valve carburetor; recoil starter or electric starter, transistorized magneto ignition (TCI) system and centrifugal mechanical governor system.
A 70.0 mm (2.76 in) cylinder bore and 58.0 mm (2.28 in) piston stroke give the Rato R225 motor a total of 223 cc of displacement. Compression ratio rating is 9.0:1. It produced 7.5 HP of horsepower at 3,600 rpm and 13.0 N·m (1.33 kg·m, 9.58 ft·lb) of torque at 2,500 rpm.
General information
| Engine Specifications | |
| Model | R225 |
| Type | 4-stroke, OHV, single cylinder |
| Displacement | 223 cm 3 (13.6 cu-in) |
| Max. horsepower | 7.5 HP at 3,600 rpm |
| Max. torque (crank PTO) | 13.0 N·m (1.33 kg·m, 9.58 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 R225 engine has cast-iron cylinder liner, dual ball bearings and steel forged and hardened crankshaft.
| Cylinder block | ||
| Compression ratio: | 9.0:1 | |
| Bore x Stroke | 70 X 58 mm (2.76 x 2.28 in) | |
| Sleeve internal diameter | 70.00 mm (2.7559 in) | |
| Piston skirt outer diameter | 69.985 mm (2.7553 in) | |
| Number of piston rings (compression / oil): | 2 / 1 | |
| Ring side clearance | Top/Second | 0.015-0.045 mm (0.0006-0.0018 in) |
| Ring end gap | Top/Second | 0.20-0.40 mm (0.008-0.016 in) |
| Oil | 0.15-0.35 mm (0.006-0.014 in) | |
| Ring width | Top/Second | 1.5 mm (0.060 in) |
| Oil | 2.0 mm (0.079 in) | |
| Connecting rod small end ID | 18.005 mm (0.7087 in) | |
| Connecting rod big end ID | 30.02 mm (1.182 in) | |
| Crankshaft crank pin outer diameter | 29.98 mm (1.180 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 | 27.7 mm (1.09 in) |
| EXHAUST | 27.75 mm (1.093 in) | |
| Valve spring free length: | 34.0 mm (1.3386 in) | |
| Camshaft journal diameter: | 13.984 mm (0.5505 in) | |
Tightening torque specs
| Tightening torque specs | |
| Connecting rod bolt | 8 Nm; 0.8 kg·m; 5.9 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 | 32 Nm; 3.2 kg·m; 23.6 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 | 3800 ± 200 rpm |
| Cylinder compression | 12.0 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 | 0.6 L |
| Carburetor | |
| Main jet | 0.85 |
| Float height | 13.7 mm (0.54 in) |
| Pilot screw opening | 2-1/8 turns out |
| Ignition system | |
| Spark plug | NGK: BPR6ES |
| 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) |
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