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
Type4-stroke, OHV, single cylinder
Displacement98 cm 3 (6.0 cu-in)
Max. horsepower3.0 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
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

Cylinder block
Compression ratio:8.5:1
Bore x Stroke56 X 40 mm (2.2 x 1.6 in)
Sleeve internal diameter56.00 mm (2.2047 in)
Piston skirt outer diameter55.965-55.985 mm (2.2033-2.2041 in)
Number of piston rings (compression / oil):2 / 1
Ring side clearanceTop/Second0.03-0.07 mm (0.0012-0.0027 in)
Ring end gapTop/Second0.15-0.30 mm (0.006-0.012 in)
Oil0.1-0.6 mm (0.0040-0.023 in)
Ring widthTop/Second1.5 mm (0.060 in)
Oil2.0 mm (0.079 in)
Connecting rod small end ID14.011-14.022 mm (0.5516-0.5520 in)
Connecting rod big end ID23.02-23.03 mm (0.9063-0.9066 in)
Crankshaft crank pin outer diameter22.975-22.985 mm (0.9045-0.9049 in)
Cylinder Head
Warpage (limit)0.10 mm (0.004 in)
Valve Arrangement:OHV
Stem outer diameter (standard):INTAKE5.465-5.480 mm (0.2151-0.2157 in)
EXHAUST5.445-5.460 mm (0.2143-0.2149 in)
Cam height:INTAKE29.4 mm (1.1575 in)
EXHAUST29.4 mm (1.1575 in)
Valve spring free length:25.0 mm (0.9842 in)

Tightening torque specs

Tightening torque specs
Connecting rod bolt12 Nm; 1.2 kg·m; 9 ft·lb
Oil dran plug22 Nm; 2.2 kg·m; 16 ft·lb
Crankcase cover12 Nm; 1.2 kg·m; 9 ft·lb
Flywheel subassembly55 Nm; 5.5 kg·m; 41 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

Maximum speed3850 ± 200 rpm
Idle speed1550 ± 150 rpm
Cylinder compression9.2 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 capacity0.35 L
Ignition system
Spark plugNGK:BPR6ES
Spark plug gap0.7-0.8 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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