Briggs and Stratton 256707

Briggs and Stratton 256707The Briggs and Stratton 256707 is a 399 cc (24.3 cu·in) single-cylinder, air-cooled, four-stroke cycle, internal combustion gasoline engine, manufactured by Briggs and Stratton.

The B&S 256707 engine has an L-head (side valve) design and a vertical PTO shaft. This engine is equipped with flo-jet carburetor, an transistor module ignition system, splash type lubrication system and 12V electric starter.

The cylinder bore is 87.30 mm (3.44 in) and the piston stroke is 66.7 mm (2.63 in). The Briggs and Stratton 256707 engine produced 10.2 PS (7.5 KW; 10.0 HP) at 3,600 rpm of maximum horsepower.

The breakdown of the engine code is as follows:

  • 25 – Displacement
  • 6 – Basic design series
  • 7 – Vertical PTO-shaft, Flo-Jet carburetor
  • 0 – Plain bearing
  • 7 – Electric starter 12V, gear drive with alternator

General information

Engine Specifications
Model B&S 256707
Type 4-stroke, L-head, single-cylinder
Displacement 399 cm 3 (24.3 cu-in)
Max. horsepower 10.2 PS (7.5 KW; 10.0 HP) at 3,600 rpm
Max. torque
Fuel system Flo-Jet carburetor
Cooling system Forced-air
Ignition system Transistor module
Lubrication system Splash type
Starting system Electric starter (12V)
Fuel used Unleaded gasoline (octane number 86 or higher)
Fuel tank capacity 2.8 liters (3.0 US.qts, 2.46 Imp. qts)

Cylinder Block and Head

Cylinder block
Compression ratio:
Bore x Stroke 87.3 mm X 66.7 mm (3.44 x 2.63 in)
Sleeve internal diameter 87.290-87.310 mm (3.4366-3.4374 in)
Number of piston rings (compression / oil): 2 / 1
Ring groove clearance 0.228 mm (0.009 in)
Ring end gap (compression ring) 0.890 mm (0.035 in)
Ring end gap (oil ring) 1.140 mm (0.045 in)
Piston pin outer diameter 20.290 mm (0.799 in)
Pin bore inner diameter 20.350 mm (0.801 in)
Connecting rod small end bearing 20.370 mm (0.802 in)
Connecting rod big end bearing 31.800 mm (1.252 in)
Crankshaft main journal diameter PTO side: 34.950 mm (1.376 in)
Magneto side: 34.950 mm (1.376 in)
Crankpin diameter 31.670 mm (1.2469 in)
Cylinder Head
Valve Arrangement: L-head (sidevalve)
Valves: 2
Cam gear journal diameter: 12.650 mm (0.498 in)
Cam lobe: 30.070 mm (1.1839 in)

Tightening torque specs

Tightening torque specs
Cylinder Head 19.0 Nm (1.9 kgf·m; 14 ft·lb)
Connecting Rod 21.0 Nm (2.1 kgf·m; 15.5 ft·lb)
Flywheel Nut 87.8 Nm (9 kgf·m; 64.8 ft·lb)
Crankcase Cover 16.0 Nm (1.6 kgf·m; 11.8 ft·lb)
Fuel Shut-Off Valve 8.0 Nm (0.8 kgf·m; 5.9 ft·lb)
Governor Lever Nut 7.0 Nm (0.7 kgf·m; 5.2 ft·lb)
Spark Plug Torque 18.0 Nm (1.8 kgf·m; 13.3 ft·lb)
Oil Drain Plug 20.0 Nm (2 kgf·m; 14.8 ft·lb)

Service Information

Engine
Max speed 3,600 rpm
Valve clearance
Intake valve clearance 0.13-0.18 mm (0.005-0.007 in)
Exhaust valve clearance 0.23-0.28 mm (0.009-0.011 in)
Oil system
Oil type API SF, SG, SH, SJ or higher
Recommended oil Summer: SAE 30, 10W-30
Winter: SAE 5W-20, 5W-30
Oil capacity (with filter) 1.4 liters (1.5 US.qts, 1.24 Imp. qts)
Ignition system
Spark plug Champion CJ-8
Spark plug gap 0.762 mm (0.030 in)
Ignition armature air gap 0.254-0.356 mm (0.010-0.014 in)

Applications

The B&S 256707 engine is used on the following lawn tractors

Model Years Produced
Wheel Horse 210-5 1990-1992
Wheel Horse 110-4 1989-1993
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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