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
ModelR225
Type4-stroke, OHV, single cylinder
Displacement223 cm 3 (13.6 cu-in)
Max. horsepower7.5 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
CarburetorFlat suction valve carburetor
Cooling systemForced-air
Ignition systemTransistorized magneto ignition (TCI)
Lubricating systemSplash
Starting systemRecoil / electric starter
Stoping systemIgnition primary circuit ground
Fuel usedUnleaded gasoline (octane number 86 or higher)
PTO shaft rotationCounterclockwise (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 Stroke70 X 58 mm (2.76 x 2.28 in)
Sleeve internal diameter70.00 mm (2.7559 in)
Piston skirt outer diameter69.985 mm (2.7553 in)
Number of piston rings (compression / oil):2 / 1
Ring side clearanceTop/Second0.015-0.045 mm (0.0006-0.0018 in)
Ring end gapTop/Second0.20-0.40 mm (0.008-0.016 in)
Oil0.15-0.35 mm (0.006-0.014 in)
Ring widthTop/Second1.5 mm (0.060 in)
Oil2.0 mm (0.079 in)
Connecting rod small end ID18.005 mm (0.7087 in)
Connecting rod big end ID30.02 mm (1.182 in)
Crankshaft crank pin outer diameter29.98 mm (1.180 in)
Cylinder Head
Warpage (limit)0.10 mm (0.004 in)
Valve Arrangement:OHV
Valves:2
Stem outer diameter (standard):INTAKE5.48 mm (0.216 in)
EXHAUST5.44 mm (0.214 in)
Cam height:INTAKE27.7 mm (1.09 in)
EXHAUST27.75 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 bolt8 Nm; 0.8 kg·m; 5.9 ft·lb
Oil dran plug22 Nm; 2.2 kg·m; 16 ft·lb
Crankcase cover28 Nm; 2.8 kg·m; 21 ft·lb
Flywheel subassembly75 Nm; 7.5 kg·m; 55 ft·lb
Cylinder head subassembly32 Nm; 3.2 kg·m; 23.6 ft·lb
Rocker shaft bolt24 Nm; 2.4 kg·m; 18 ft·lb
Cylinder head cover10 Nm; 1.0 kg·m; 7 ft·lb
Spark plug28 Nm; 2.8 kg·m; 21 ft·lb
Ignition coil10 Nm; 1.0 kg·m; 7 ft·lb

Service Information

Engine
Maximum speed3800 ± 200 rpm
Cylinder compression12.0 kg/cm2 at 1400 rpm
Valve clearance
Intake valve clearance0.15±0.02 mm (0.006±0.001 in)
Exhaust valve clearance0.20±0.02 mm (0.008±0.001 in)
Oil system
Oil type4-stroke or an equivalent (SJ)
Recommended oilSAE 10W-30, 15W-40
Oil capacity0.6 L
Carburetor
Main jet0.85
Float height13.7 mm (0.54 in)
Pilot screw opening2-1/8 turns out
Ignition system
Spark plugNGK: BPR6ES
Spark plug gap0.7-0.8 mm (0.028-0.031 in)
Primary ignition coil resistance0.8-1.0 Ω
Secondary ignition coil resistance5.9-7.1 kΩ
Ignition coil air gap0.4 ± 0.2 (0.016 ± 0.008)
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