Subaru-Robin EX13D

Subaru-Robin EX13D engineThe Subaru-Robin EX13D is a 0.1 L (126 cc, 7.69 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 Subaru EX13D engine has a single cylinder, heavy-duty chain-driven overhead camshaft (OHC) system, sophisticated mechanical compression release system, and 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 EX13D is equipped with 2.7 L (0.71 US. gal. 0.59 Imp. gal.) fuel tank.

The Subaru-Robin EX13D engine produced 4.4 PS (3.2 kW; 4.3 HP) at 4,000 rpm of maximum horsepower and 8.1 N·m (0.8 kg·m, 6 ft·lb) at 2,500 rpm of maximum torque.

General information

Engine Specifications
Engine model EX13D
Engine type 4-stroke, OHC, single-cylinder
Displacement 126 cm3, (7.69 cu·in)
Max. horsepower 4.4 PS (3.2 kW; 4.3 HP) at 4,000 rpm
Max. torque 8.1 N·m (0.8 kg·m, 6 ft·lb) at 2,500 rpm
Cooling system Forced air
Air cleaner Dual Elements, Pre-Cleaner, Oil Bath, Remote
Lubricating system Splash
Ignition system Transistorized magneto ignition
Fuel system Horizontal draft, float type carburetor
Fuel consumption 367 g/kWH
Fuel tank capacity 2.7 L (0.71 US. gal. 0.59 Imp. gal.)
Fuel used Unleaded gasoline (octane number 86 or higher)
Starting system Recoil starter
Stoping system Ignition primary circuit ground
Governor Centrifugal govervor
PTO shaft rotation Counterclockwise (from PTO shaft side)
Dimensions (L x W X H) 297 x 341 x 318 mm (11.7 x 13.4 x 12.5 in)
Dry weight 14.0 kg (30.9 lbs)

Cylinder Block and Head

A 58.0 mm (2.28 in) cylinder bore and 48.0 mm (1.89 in) piston stroke give the EX13D engine a total of 126 cc of displacement. 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: 58.0 mm (2.28 in)
Piston stroke: 48.0 mm (1.89 in)
Cylinder internal diameter (standard): 58.000-58.020 mm (2.2835-2.2842 in)
Piston skirt outer diameter (standard): 57.980-58.000 mm (2.2827-2.2835 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): 13.010-13.020 mm (0.5122-0.5126 in)
Piston pin diameter: 12.991-13.009 mm (0.5115-0.5122 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): 0.020-0.075 mm (0.0008-0.003 in)
Ring end gap (Top): 0.15-0.35 mm (0.0059-0.0138 in)
Ring end gap (Second): 0.15-0.35 mm (0.0059-0.0138 in)
Ring end gap (Oil): 0.20-0.40 mm (0.0079-0.0157 in)
Number of main bearings: 2
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 EX13D, refilling oil capacity is 0.6 L (0.63 US. qt, 0.53 Imp. qt.). Recommended spark plugs are NGK BR-6HS or CHAMPION RL86C 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 and exhaust valves. Standard cylinder compression is 3.5 kg/cm2 at 500 rpm.

Compression pressure
Cylinder compression: 3.5 kg/cm2 at 500 rpm
Valve clearance
Intake valve clearance: 0.12-0.15 mm (0.0047-0.0059 in)
Exhaust valve clearance: 0.12-0.15 mm (0.0047-0.0059 in)
Oil system
Lubrication system: Splash
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;
CHAMPION: RL86C
Spark plug gap: 0.6-0.7 mm (0.0236-0.0276 in)
Spark plug torque: New: 15 N·m; 1.5 kg·m; 10.8 ft·lb
Re-tightening: 25 N·m; 2.5 kg·m; 18.4 ft·lb

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