The Briggs and Stratton 31E777 is a 501 cc (30.6 cu·in) single-cylinder air-cooled four-stroke internal combustion gasoline engine, manufactured by Briggs and Stratton.
The B&S 31E777 engine has an OHV (overhead) design and a vertical PTO shaft. This engine is equipped with float type carburetor and an electronic ignition system. The B&S 31E777 engine used a paper air filter with a foam pre-cleaner. It is equipped with an electric starter (12V).
The cylinder bore is 90.6 mm (3.57 in) and the piston stroke is 77.8 mm (3.06 in). This engine produced 16.2 PS (11.9 KW; 16.0 HP) at 3,600 rpm of horsepower.
The breakdown of the engine code is as follows:
- 31 – Displacement
- E – Basic design series
- 7 – Vertical PTO-shaft
- 7 – Plain bearing, Pressure lubrication
- 7 – Electric starter
General information
| Engine Specifications | |
| Model | B&S 31E777 |
| Type | 4-stroke, OHV, single-cylinder |
| Displacement | 501 cm 3 (30.6 cu-in) |
| Max. horsepower | 16.2 PS (11.9 KW; 16.0 HP) at 3,600 rpm |
| Max. torque | – |
| Fuel system | Float type carburetor |
| Cooling system | Forced-air |
| Ignition system | Electronic |
| Lubricating system | Full pressure |
| Starting system | Electric starter |
| Fuel used | Gasoline |
| Fuel tank capacity | – |
Cylinder Block and Head
| Cylinder block | ||
| Compression ratio: | – | |
| Bore x Stroke | 90.6 mm X 77.8 mm (3.57 x 3.06 in) | |
| Sleeve internal diameter | 90.500-90.600 mm (3.563-3.5669 in) | |
| Number of piston rings (compression / oil): | 2 / 1 | |
| Side clearance | Top | 0.05-0.12 mm (0.002-0.005 in) |
| Second | 0.05-0.12 mm (0.002-0.005 in) | |
| Oil | 0.05-0.12 mm (0.002-0.005 in) | |
| Ring end gap | Top | 0.150-0.230 mm (0.0059-0.0091 in) |
| Second | 0.350-0.450 mm (0.0138-0.0177 in) | |
| Oil | 0.150-0.250 mm (0.0059-0.0098 in) | |
| Connecting rod small end ID | 20.330-20.370 mm (0.8004-0.802 in) | |
| Piston pin outer diameter | 20.310-20.290 mm (0.7996-0.7988 in) | |
| Cylinder Head | ||
| Valve Arrangement: | OHV (overhead) | |
| Valves: | 2 | |
| Valve steam diameter | INTAKE | 5.920-5.970 mm (0.233-0.235 in) |
| EXHAUST | 5.920-5.970 mm (0.233-0.235 in) | |
Tightening torque specs
| Tightening torque specs | |
| Air cleaner base | 6.0 Nm; 4.4 ft·lb |
| Alternator | 2.0 Nm; 1.5 ft·lb |
| Armature | 3.0 Nm; 2.2 ft·lb |
| Blower housings | 10.0 Nm; 7.4 ft·lb |
| Blower housing brackets | 10.0 Nm; 7.4 ft·lb |
| Breather | 3.0 Nm; 2.2 ft·lb |
| Carburetor to intake manifold | 8.0 Nm; 5.9 ft·lb |
| Carburetor solenoid | 5.0 Nm; 3.7 ft·lb |
| Connecting rod | 17.0 Nm; 12.6 ft·lb |
| Control bracket | 5.0 Nm; 3.7 ft·lb |
| Crankcase sump | 25.0 Nm; 18.5 ft·lb |
| Cylinder head | 25.0 Nm; 18.5 ft·lb |
| Cylinder shield | 5.0 Nm; 3.7 ft·lb |
| Exhaust manifold / adapter | 19.0 Nm; 14.0 ft·lb |
| Flywheel nut | 135.0 Nm; 100.0 ft·lb |
| Flywheel fan | 16.0 Nm; 11.9 ft·lb |
| Fuel pump | 10.0 Nm; 7.4 ft·lb |
| Governor lever nut | 5.0 Nm; 3.7 ft·lb |
| Intake manifold to cylinder head | 10.0 Nm; 7.4 ft·lb |
| Muffler | 10.0 Nm; 7.4 ft·lb |
| Oil drain plug | 11.0 Nm; 8.1 ft·lb |
| Oil fill tube | 10.0 Nm; 7.4 ft·lb |
| Oil pump cover | 10.0 Nm; 7.4 ft·lb |
| Regulator / Rectifier | 5.0 Nm; 3.7 ft·lb |
| Rewind starter | 3.0 Nm; 2.2 ft·lb |
| Rocker ball set screw or nut | 5.0 Nm; 3.7 ft·lb |
| Rocker cover | 7.0 Nm; 5.2 ft·lb |
| Starter motor | 16.0 Nm; 11.9 ft·lb |
Service Information
| Engine | |
| Max speed | 3,600 rpm |
| Valve clearance | |
| Intake valve clearance | 0.08-0.13 mm (0.003-0.005 in) |
| Exhaust valve clearance | 0.13-0.18 mm (0.005-0.007 in) |
| Oil system | |
| Oil type | API SF, SG, SH, SJ or higher |
| Recommended oil |
Summer: SAE 30, 10W-30 Winter: SAE 5W-30 |
| Oil capacity (with filter) | 1.42 L (1.5 US. qt, 1.25 Imp. qt.) |
| Ignition system | |
| Spark plug | Champion RC12YC or Champion QC12YC |
| Spark plug gap | 0.7-0.8 mm (0.0276-0.0315 in) |
Can I purchase a 31E777-0130-E1 engine to replace my original