Subaru-Robin EX35D

Subaru-Robin EX35D engineThe Robin-Subaru EX35D is a 404 cc, (24.6 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 EX35D engine has a single-cylinder, heavy-duty chain-driven overhead camshaft (OHC) system, a sophisticated mechanical compression release system, and a recoil or electric starter. This engine used a horizontal draft, float type carburetor, transistorized magneto ignition system, splash type lubricating system, and forced-air cooling system. The EX35D is equipped with a 7.0 L (1.85 US. gal. 1.54 Imp. gal.) fuel tank.

The EX35D engine produced 10.1 PS (7.4 kW; 9.9 HP) at 3,600 rpm of maximum net power and 12.0 PS (8.8 kW; 11.8 HP) at 3,600 rpm of maximum gross power. Peak torque is 26.0 N·m (2.7 kg·m, 19.2 ft·lb) at 2,400 rpm.

General information

Engine Specifications
Engine model Robin-Subaru EX35D
Engine type 4-stroke, OHC, single-cylinder
Displacement 404 cm3, (24.65 cu·in)
Max. horsepower 10.0 PS (7.4 kW; 10.0 HP) at 3,600 rpm
Max. torque 26.0 N·m (2.7 kg·m, 19.2 ft·lb) at 2,400 rpm
Cooling system Forced air
Lubricating system Splash type
Ignition system Transistorized magneto ignition
Fuel system Horizontal draft, float type carburetor
Fuel tank capacity 7.0 L (1.85 US. gal. 1.54 Imp. gal.)
Fuel used Unleaded gasoline (octane number 86 or higher)
Starting system Recoil or electric starter (option)
Stoping system Ignition primary circuit ground
Governor Centrifugal govervor
Charging capacity 12-1A, 3A, 16.7A (option)
PTO shaft rotation Counterclockwise (from PTO shaft side)
Dimensions (L x W X H) 389 x 450 x 447 mm (15.3 x 17.7 x 17.6 in)
Dry weight 33.0 kg (72.8 lbs)

Cylinder Block and Head

Cylinder bore and piston stroke are 89.0 mm (3.5 in) and 65.0 mm (2.56 in), respectively. Compression ratio rating is 8.3:1. 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 single compression rings.

Cylinder block
Compression ratio: 8.3:1
Cylinder bore: 89.0 mm (3.5 in)
Piston stroke: 65.0 mm (2.56 in)
Cylinder internal diameter (standard): 89.000-89.022 mm (3.5039-3.5048 in)
Piston skirt outer diameter (standard): 88.980-89.000 mm (3.5031-3.5039 in)
Number of piston rings (compression / oil): 1/1
Connecting rod big end diameter (standard): 38.000-38.016 mm (1.4961-1.4967 in)
Connecting rod small end diameter (standard): 21.010-21.023 mm (0.8272-0.8277 in)
Piston pin diameter: 20.992-21.000 mm (0.8265-0.8268 in)
Side clearance (Top): 0.050-0.080 mm (0.002-0.0031 in)
Side clearance (Oil): 0.030-0.125 mm (0.0012-0.0049 in)
Ring end gap (Top): 0.10-0.25 mm (0.0039-0.0098 in)
Ring end gap (Oil): 0.15-0.55 mm (0.0059-0.0217 in)
Crankshaft main journal diameter: 34.986-34.997 mm (1.3774-1.3778 in)
Crankpin journal diameter: 37.956-37.970 mm (1.4943-1.4949 in)
Crankshaft center distance: 32.5 mm (1.28 in)
Cylinder head
Valve arrangement: OHC, chain driven
Valves: 2
Valve steam diameter (INTAKE): 5.970-5.985 mm (0.235-0.2356 in)
Valve steam diameter (EXHAUST): 5.970-5.985 mm (0.235-0.2356 in)
Valve spring free length (INTAKE): 36.5 mm (1.437 in)
Valve spring free length (EXHAUST): 36.5 mm (1.437 in)
Camshaft lobe height (INTAKE): 35.658-35.758 mm (1.4039-1.4078 in)
Camshaft lobe height (EXHAUST): 39.408-39.508 mm (1.5515-1.5554 in)

Tightening torque

Tightening torque settings
Cylinder head M10 × 75 flange bolt (Re-use): 29-31 Nm; 2.9-3.1 kg·m; 21.0-22.4 ft·lb
Cylinder head M10 × 75 flange bolt (New): 37-39 Nm; 3.7-3.9 kg·m; 26.7-28.2 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: 22-27 Nm; 2.2-2.7 kg·m; 16.3-19.9 ft·lb
Main bearing cover bolts: 22-24 Nm; 2.2-2.4 kg·m; 16.2-17.7 ft·lb
Flywheel nut: 100-120 Nm; 10.0-12.0 kg·m; 72.3-86.8 ft·lb

Service Data

The 4-stroke engine oil, API service classification SE oil with a viscosity of SAE 10W-30 is recommended for the EX35D, refilling oil capacity is 1.2 L (1.27 US. qt, 1.06 Imp. qt.). Recommended spark plug is NGK BR-6HS 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 0.12-0.15 mm (0.0047-0.0059 in) for exhaust valves. Standard cylinder compression is 4.5 kg/cm2 at 500 rpm.

Cylinder compression
Cylinder compression: 4.5 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: 7-11 ml/h
Oil type: 4-stroke engine oil, API service classification SE
Recommended oil: SAE 10W-30
Oil capacity: 1.2 L (1.27 US. qt, 1.06 Imp. qt.)
Fuel system
Type: Horizontal draft, float type carburetor
Main jet: URETHANE: 109, DUAL: 107
Slow jet: URETHANE: 40, DUAL: 44
Ignition system
Type: Transistorized magneto ignition
Spark plug: NGK BR-6HS
Spark plug gap: 0.6-0.7 mm (0.0236-0.0276 in)
Spark plug torque: 25 N·m (2.5 kg·m, 18.4 ft·lb)
Ignition coil air gap 0.3-0.5 mm (0.0118-0.0118 in)

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