Rato R100

The 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

Engine
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)