Rato R225

Rato R225The 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)
Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

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