Subaru-Robin SP170

Subaru-Robin SP170 engineThe Subaru-Robin SP170 is a 0.2 L (169 cc, 10.31 cu·in) natural aspirated single-cylinder four-stroke air-cooled internal combustion small gasoline engine with a horizontal shaft, manufactured by the Industrial Products division of Subaru Corporation for general-purpose applications.

The Robin-Subaru SP170 engine has a single-cylinder, heavy-duty chain-driven overhead camshaft (OHC) system, a sophisticated mechanical compression release system, and a heavy-duty recoil starter. This engine used a horizontal draft, float type carburetor, transistorized magneto ignition system, splash type lubricating system, and forced-air cooling system. The SP170 is equipped with a 3.6 L (0.95 US. gal. 0.79 Imp. gal.) fuel tank.

This engine produced 5.7 PS (4.2 kW; 5.6 HP) at 4,000 rpm of horsepower and 11.3 N·m (1.2 kg·m, 8.3 ft·lb) at 2,500 rpm of torque.

General information

Engine Specifications
Engine model Robin-Subaru SP170
Engine type 4-stroke, OHC, single-cylinder
Displacement 169 cm3, (10.31 cu·in)
Max. horsepower 5.7 PS (4.2 kW; 5.6 HP) at 4,000 rpm
Max. torque 11.3 N·m (1.2 kg·m, 8.3 ft·lb) at 2,500 rpm
Cooling system Forced air
Lubricating system Splash type
Ignition system Transistorized magneto ignition
Fuel system Horizontal draft, float type carburetor
Fuel consumption 367 g/kWH
Fuel tank capacity 3.6 L (0.95 US. gal. 0.79 Imp. gal.)
Fuel used Unleaded gasoline (octane number 86 or higher)
Starting system Recoil
Stoping system Ignition primary circuit ground
Governor Centrifugal govervor
PTO shaft rotation Counterclockwise (from PTO shaft side)
Dimensions (L x W X H) 304 x 354 x 335 mm (12 x 13.9 x 13.2 in)
Dry weight 15.0 kg (33.1 lbs)

Cylinder Block and Head

It has a 67.0 mm (2.64 in) cylinder bore and 48.0 mm (1.89 in) piston stroke. Compression ratio rating is 8.5:1. The engine uses cast iron cylinder liner and large ball bearings on both ends of crankshaft for maximum stability under demanding loads. The piston is equipped with single oil and two compression rings.

Cylinder block
Compression ratio: 8.5:1
Cylinder bore: 67.0 mm (2.64 in)
Piston stroke: 48.0 mm (1.89 in)
Cylinder internal diameter (standard): 67.000-67.019 mm (2.6378-2.6385 in)
Piston skirt outer diameter (standard): 66.960-67.000 mm (2.6362-2.6378 in)
Number of piston rings (compression / oil): 2/1
Connecting rod big end diameter (standard): 30.000-30.016 mm (1.1811-1.1817 in)
Connecting rod small end diameter (standard): 16.010-16.021 mm (0.6303-0.6307 in)
Piston pin diameter: 15.992-16.000 mm (0.6296-0.6299 in)
Side clearance (Top): 0.035-0.080 mm (0.0014-0.0031 in)
Side clearance (Second): 0.035-0.080 mm (0.0014-0.0031 in)
Side clearance (Oil): 0.010-0.065 mm (0.0004-0.0026 in)
Ring end gap (Top): 0.15-0.30 mm (0.0059-0.0118 in)
Ring end gap (Second): 0.20-0.40 mm (0.0079-0.0157 in)
Ring end gap (Oil): 0.05-0.25 mm (0.002-0.0098 in)
Crankshaft main journal diameter №1: 27.988-24.997 mm (1.1019-0.9841 in)
Crankshaft main journal diameter №2: 24.988-24.997 mm (0.9838-0.9841 in)
Crankpin journal diameter: 29.967-29.980 mm (1.1798-1.1803 in)
Crankshaft center distance: 24 mm (0.945 in)
Cylinder head
Valve arrangement: OHC, chain driven
Valves: 2
Valve steam diameter (INTAKE): 5.440-5.455 mm (0.2142-0.2148 in)
Valve steam diameter (EXHAUST): 5.425-5.445 mm (0.2136-0.2144 in)
Valve spring free length (INTAKE): 27.4 mm (1.0787 in)
Valve spring free length (EXHAUST): 27.4 mm (1.0787 in)
Camshaft lobe height (INTAKE): 29.028-29.128 mm (1.1428-1.1468 in)
Camshaft lobe height (EXHAUST): 29.028-29.128 mm (1.1428-1.1468 in)

Tightening torque

Tightening torque settings
Cylinder head M8 × 68 flange bolt (Re-use): 25-27 Nm; 2.5-2.7 kg·m; 18.1-19.5 ft·lb
Cylinder head M8 × 68 flange bolt (New): 28-30 Nm; 2.8-3.0 kg·m; 20.3-21.7 ft·lb
Cylinder head M8 × 35 flange bolt: 17-19 Nm; 1.7-1.9 kg·m; 12.3-13.7 ft·lb
Connecting rod bolt: 13-15 Nm; 1.3-1.5 kg·m; 9.4-10.8 ft·lb
Main bearing cover bolts: 22-24 Nm; 2.2-2.4 kg·m; 16.2-17.7 ft·lb
Flywheel nut: 59-64 Nm; 5.9-6.4 kg·m; 42.7-46.3 ft·lb

Service Data

The 4-stroke engine oil, API service classification SE oil with a viscosity of SAE 10W-30 or 10W-40 is recommended for the SP170, refilling oil capacity is 0.6 L (0.63 US. qt, 0.53 Imp. qt.). Recommended spark plugs are NGK BR-6HS or TORCH E6RC with 0.6-0.7 mm (0.0236-0.0276 in) spark plug gap.

The valve clearance is 0.12-0.15 mm (0.0047-0.0059 in) for intake valves and exhaust valves. Standard cylinder compression is 3.5 kg/cm2 at 500 rpm.

Cylinder compression: 3.5 kg/cm2 at 500 rpm
Valve clearance
Intake valve clearance (COLD): 0.12-0.15 mm (0.0047-0.0059 in)
Exhaust valve clearance (COLD): 0.12-0.15 mm (0.0047-0.0059 in)
Oil system
Lubrication system: Splash type
Oil consupumtion: 5-10 ml/h
Oil type: 4-stroke engine oil, API service classification SE
Recommended oil: SAE 10W-30 or 10W-40
Oil capacity: 0.6 L (0.63 US. qt, 0.53 Imp. qt.)
Fuel system
Type: Horizontal draft, float type carburetor
Ignition system
Type: Transistorized magneto ignition
Spark plug: NGK: BR-6HS;
TORCH: E6RC
Spark plug gap: 0.6-0.7 mm (0.0236-0.0276 in)

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