Rato R100

Rato R100The Rato R100 is a 98 cc (6.0 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 R100 engine has an OHV design; flat suction valve carburetor; recoil starter or electric starter and transistorized magneto ignition (TCI) system.

A 56.0 mm (2.2 in) cylinder bore and 40.0 mm (1.60 in) piston stroke give the Rato R100 motor a total of 98 cc of displacement. Compression ratio rating is 8.5±0.3:1. It produced 3.0 HP of horsepower at 3,600 rpm and 4.7 N·m (0.48 kg·m, 3.46 ft·lb) of torque at 2,500 rpm.

General information

Engine Specifications
Model R100
Type 4-stroke, OHV, single cylinder
Displacement 98 cm 3 (6.0 cu-in)
Max. horsepower 3.0 HP at 3,600 rpm
Max. torque (crank PTO) 4.7 N·m (0.48 kg·m, 3.46 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

Cylinder block
Compression ratio: 8.5:1
Bore x Stroke 56 X 40 mm (2.2 x 1.6 in)
Sleeve internal diameter 56.00 mm (2.2047 in)
Piston skirt outer diameter 55.965-55.985 mm (2.2033-2.2041 in)
Number of piston rings (compression / oil): 2 / 1
Ring side clearance Top/Second 0.03-0.07 mm (0.0012-0.0027 in)
Ring end gap Top/Second 0.15-0.30 mm (0.006-0.012 in)
Oil 0.1-0.6 mm (0.0040-0.023 in)
Ring width Top/Second 1.5 mm (0.060 in)
Oil 2.0 mm (0.079 in)
Connecting rod small end ID 14.011-14.022 mm (0.5516-0.5520 in)
Connecting rod big end ID 23.02-23.03 mm (0.9063-0.9066 in)
Crankshaft crank pin outer diameter 22.975-22.985 mm (0.9045-0.9049 in)
Cylinder Head
Warpage (limit) 0.10 mm (0.004 in)
Valve Arrangement: OHV
Valves: 2
Stem outer diameter (standard): INTAKE 5.465-5.480 mm (0.2151-0.2157 in)
EXHAUST 5.445-5.460 mm (0.2143-0.2149 in)
Cam height: INTAKE 29.4 mm (1.1575 in)
EXHAUST 29.4 mm (1.1575 in)
Valve spring free length: 25.0 mm (0.9842 in)

Tightening torque specs

Tightening torque specs
Connecting rod bolt 12 Nm; 1.2 kg·m; 9 ft·lb
Oil dran plug 22 Nm; 2.2 kg·m; 16 ft·lb
Crankcase cover 12 Nm; 1.2 kg·m; 9 ft·lb
Flywheel subassembly 55 Nm; 5.5 kg·m; 41 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

Maximum speed 3850 ± 200 rpm
Idle speed 1550 ± 150 rpm
Cylinder compression 9.2 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 0.35 L
Ignition system
Spark plug NGK:BPR6ES
Spark plug gap 0.7-0.8 mm (0.028-0.031 in)
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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We try to use verified sources and official documentation, however, differences between sources or errors in entering information may occur. We do not provide advice on technical issues related to the engines operation or repair. We do not recommend using provided information for engines repairing engines or spare parts ordering, use only official service manuals and spare-parts catalogs.

1 Comment

  1. The spark plug mentioned above is wrong,NGK CR5HSB is the correct plug for this machine.BPR6ES will not fit,please edit this fault.

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