Subaru-Robin SP170

SP170The Subaru-Robin SP170 is a 169 cc (10.31 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 SP170 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.

Bore and stroke are 67.0 mm (2.64 in) and 48.0 mm (1.89 in), respectively. Compression ratio rating is 8.5:1. The engine produced 5.7 PS (4.2 kW; 5.6 HP) at 4,000 rpm of maximum horsepower and 3.5 PS (2.6 kW; 3.5 HP) at 3,000 rpm or 3.9 PS (2.9 kW; 3.9 HP) at 3,600 rpm of continuous output power. Maximum torque is 11.3 N·m (1.2 kg·m, 8.3 ft·lb) at 2,500 rpm.

General information

Engine Specifications
Type4-stroke, OHC, single cylinder
Displacement169 cm 3 (10.31 cu-in)
Max. horsepower5.7 PS (4.2 kW; 5.6 HP) at 4,000 rpm
Max. torque (crank PTO)11.3 N·m (1.2 kg·m, 8.3 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 capacity3.6 L (0.95 US. gal. 0.79 Imp. gal.)
Fuel consumption367 g/kWH
PTO shaft rotationCounterclockwise (from PTO shaft side)

Cylinder Block and Head

The SP170 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 Stroke67.0 X 48.0 mm (2.64 x 1.89 in)
Sleeve internal diameter67.000-67.019 mm (2.6378-2.6385 in)
Piston skirt outer diameter66.960-67.000 mm (2.6362-2.6378 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)
Oil0.010-0.065 mm (0.0004-0.0026 in)
Ring end gapTop0.15-0.30 mm (0.0059-0.0118 in)
Second0.20-0.40 mm (0.0079-0.0157 in)
Oil0.05-0.25 mm (0.002-0.0098 in)
Connecting rod small end ID16.010-16.021 mm (0.6303-0.6307 in)
Connecting rod big end ID30.000-30.016 mm (1.1811-1.1817 in)
Piston pin outer diameter15.992-16.000 mm (0.6296-0.6299 in)
Crankshaft crankpin outer diameter29.967-29.980 mm (1.1798-1.1803 in)
Crankshaft crankpin outer 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)
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  1. I have a SP 170 engine. what is the recommended compression for this engine? I get a reading of 50, is that acceptable?

  2. I have a SP 170 engine. what is the recommended compression for this engine? I get 50 pounds. is that acceptable?

  3. All well and good, but . . . I cannot find on 50+ listings . . . how much oil I
    should install in my 6hp Robin pressure washer when I change my oil. What the heck is the mystery, and where should I look?
    Oh yeah, what is .63 of a U.S. Qt in real numbersm as I do not have a beakeer that show that typ/kind of amts.

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