Subaru-Robin EX13D

Subaru-Robin EX13DThe Subaru-Robin EX13D is a 126 cc (7.69 cu-in) single-cylinder air-cooled 4-stroke internal combustion small gasoline engine manufactured by Industrial Products division of Subaru Corporation for general-purpose applications.

The Subaru-Robin EX13D engine has an OHС (overhead camshaft) design; high compression ratio for better fuel efficiency; horizontal draft, float type carburetor; recoil starter and transistorized magneto ignition system.

Cylinder bore is 58.0 mm (2.28 in) and piston stroke is 48.0 mm (1.89 in), compression ratio rating is 8.5:1. The engine produced 2.9 4.4 PS (3.2 kW; 4.3 HP) at 4,000 rpm of maximum horsepower and 2.6 PS (1.9 kW; 2.5 HP) at 3,000 rpm or 3.0 PS (2.2 kW; 3.0 HP) at 3,600 rpm of continuous output power. Maximum torque is 8.1 N·m (0.8 kg·m, 6 ft·lb) at 2,500 rpm.

General information

Engine Specifications
Type4-stroke, OHC, single cylinder
Displacement126 cm 3 (7.7 cu-in)
Max. horsepower4.4 PS (3.2 kW; 4.3 HP) at 4,000 rpm
Max. torque (crank PTO)8.1 N·m (0.8 kg·m, 6 ft·lb) at 2,500 rpm
CarburetorHorizontal draft, float type carburetor
Cooling systemForced-air
Ignition systemTransistorized magneto ignition
Lubricating systemSplash
Starting systemRecoil starter
Stoping systemIgnition primary circuit ground
Fuel usedUnleaded gasoline (octane number 86 or higher)
Fuel tank capacity2.7 L (0.71 US. gal. 0.59 Imp. gal.)
Fuel consumption367 g/kWH
PTO shaft rotationCounterclockwise (from PTO shaft side)

Cylinder Block and Head

The EX13D has cast iron cylinder sleeve, ball bearing supported forged steel crankshaft, improved piston design. The piston has two compression rings and one oil ring.

Cylinder block
Compression ratio:8.5:1
Bore x Stroke58.0 X 48.0 mm (2.28 x 1.89 in)
Sleeve internal diameter58.000-58.020 mm (2.2835-2.2842 in)
Piston skirt outer diameter57.980-58.000 mm (2.2827-2.2835 in)
Number of piston rings (compression / oil):2 / 1
Ring side clearanceTop0.035-0.080 mm (0.0014-0.0031 in))
Second0.035-0.080 mm (0.0014-0.0031 in)
Oil0.020-0.075 mm (0.0008-0.003 in)
Ring end gapTop/Second0.15-0.35 mm (0.0059-0.0138 in)
Oil0.20-0.40 mm (0.0079-0.0157 in)
Connecting rod small end ID13.010-13.020 mm (0.5122-0.5126 in)
Connecting rod big end ID30.000-30.016 mm (1.1811-1.1817 in)
Piston pin outer diameter12.991-13.009 mm (0.5115-0.5122 in)
Crankshaft crankpin outer diameter29.967-29.980 mm (1.1798-1.1803 in)
Crankshaft main journal diameter№127.988-24.997 mm (1.1019-0.9841 in)
№224.988-24.997 mm (0.9838-0.9841 in)
Cylinder Head
Warpage (limit)0.10 mm (0.004 in)
Valve Arrangement:OHC
Stem outer diameter (standard):INTAKE5.440-5.455 mm (0.2142-0.2148 in)
EXHAUST5.425-5.445 mm (0.2136-0.2144 in)
Valve spring free length:27.4 mm (1.0787 in)
Camshaft lobe height:INTAKE29.028-29.128 mm (1.1428-1.1468 in)
EXHAUST29.028-29.128 mm (1.1428-1.1468 in)

Tightening torque specs

Tightening torque specs
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 bolt17-19 Nm; 1.7-1.9 kg·m; 12.3-13.7 ft·lb
Connecting rod bolt13-15 Nm; 1.3-1.5 kg·m; 9.4-10.8 ft·lb
Main bearing cover bolts22-24 Nm; 2.2-2.4 kg·m; 16.2-17.7 ft·lb
Flywheel nut59-64 Nm; 5.9-6.4 kg·m; 42.7-46.3 ft·lb

Service Information

Cylinder compression3.5 kg/cm2
Valve clearance
Intake valve clearance0.12-0.15 mm (0.0047-0.0059 in)
Exhaust valve clearance0.12-0.15 mm (0.0047-0.0059 in)
Oil system
Oil type4-stroke or an equivalent (SE or SF)
Recommended oilSAE 10W-30
Oil capacity0.6 L (0.63 US. qt, 0.53 Imp. qt.)
Ignition system
Spark plug NGK: BR-6HS;
Spark plug gap0.6-0.7 mm (0.0236-0.0276 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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  1. I’m looking for guidance as to number and shape of the carburettor gaskets for the robin EX13 especially the complicated one 2nd from the engine block, thanks for helping me so far

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