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Briggs and Stratton 31R977 Specs
The Briggs and Stratton 31R977 is a 501 cc (30.6 cubic inches) single-cylinder air-cooled 4-cycle internal combustion gasoline engine, manufactured by Briggs and Stratton.
The engine has an OHV (overhead) design and a vertical PTO shaft. This engine is equipped with float type carburetor, integral type fuel pump and an electronic ignition system. The Briggs 31R977 engine used a paper cartridge air filter. 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 output 17.7 PS (13.0 KW; 17.5 HP) at 3,600 rpm of maximum power.
Engine code identification:
31 - Total displacement,
R - Basic design series,
9 - Vertical PTO-shaft,
7 - Plain bearing, Pressure lubrication,
7 - Electric starter.
| General Technical Data |
Engine Model ................ Briggs and Stratton 31R977 Intek
Engine Type ................ 4-cycle single cylinder OHV vertical shaft air-cooled gasoline engine
Number of Cylinders ................ 1
Displacement, cu.in (cc) ................ 30.5 (500)
Cylinder Bore, in (mm) ................ 3.56 (91.0)
Piston Stroke, in (mm) ................ 3.06 (78.0)
Rated Engine Power, hp (kW) ................ 17.5 (13.0)
Rated Engine Speed, rpm ................ 3600
Idle Speed, rpm ................ 1750
Cylinder Bore Type ................ Cast iron sleeve
Lubrication System ................ Oil pump with filter
Air Cleaner ................ Dual element
Cooling System ................ Forced air
Ignition System ................ Electronic
Starting System ................ Electric starter
Electrical System Rating, Volts ................ 12
Charging System Rating, Amps ................ 9
| Fuel System |
Fuel System Type ................ Carburetor
Carburetor Type ................ Float
Fuel Pump ................ Integral type
Governor Type ................ Mechanical
Fuel Type ................ Gasoline
| Dimensions and Weight |
Overall Length, in (mm) ................ 18.3 (462)
Overall Width, in (mm) ................ 14.8 (375)
Overall Height, in (mm) ................ 12.8 (324)
Net Weight, lbs (kg) ................ 79.2 (36.0)
| Cylinder Block |
Cylinder Bore Inside Diameter (Standard), in (mm) ................ 3.563 (90.50)
Cylinder Bore Inside Diameter (Maximum), in (mm) ................ 3.567 (90.60)
Cylinder Bore (Out-Of-Round), in (mm) ................ 0.0015 (0.04)
Main Bearing Bore Diameter (Cylinder Block), in (mm) ................ 1.3795 (35.04)
Main Bearing Bore Diameter (Crankcase Cover), in (mm) ................ 1.063 (27.00)
Camshaft Bearing Bore Diameter (Cylinder Block), in (mm) ................ 0.5011 (15.88)
Camshaft Bearing Bore Diameter (Crankcase Cover), in (mm) ................ 0.501 (12.72)
Crank Pin Journal Outside Diameter (Standard), in (mm) ................ 1.4982 (38.05)
Crank Pin Journal Outside Diameter (Wear Limit), in (mm) ................ 1.497 (31.02)
Crankshaft Journal Outside Diameter (Magneto Side), in (mm) ................ 1.3775 (35.00)
Crankshaft Journal Outside Diameter (PTO Side), in (mm) ................ 1.3775 (35.00)
Crankshaft Eccentrics (Standard), in (mm) ................ 2.2045 (55.91)
Crankshaft Eccentrics (Wear Limit), in (mm) ................ 2.202 (55.93)
Crankshaft End Play, in (mm) ................ 0.002-0.023 (0.05-0.58)
Camshaft Journal Outside Diameter (Magneto Side), in (mm) ................ 0.499 (12.67)
Camshaft Journal Outside Diameter (PTO Side), in (mm) ................ 0.499 (12.67)
Connecting Rod Big End Inside Diameter (Standard), in (mm) ................ 1.2505 (31.76)
Connecting Rod Big End Inside Diameter (Wear Limit), in (mm) ................ 1.2525 (31.81)
Connecting Rod Small End Inside Diameter (Standard), in (mm) ................ 0.8006 (20.33)
Connecting Rod Small End Inside Diameter (Wear Limit), in (mm) ................ 0.802 (20.37)
Counterweight Bearings Diameter (Standard), in (mm) ................ 2.207 (56.05)
Counterweight Bearings Diameter (Wear Limit), in (mm) ................ 2.210 (56.13)
| Cylinder Head and Valves |
Cylinder Head (Max Out of Flatness), in (mm) ................ 0.004 (0.10)
Intake Valve Clearance, in (mm) ................ 0.003-0.005 (0.08-0.13)
Exhaust Valve Clearance, in (mm) ................ 0.005-0.007 (0.13-0.18)
Valve Guide Inside Diameter (Standard), in (mm) ................ 0.237 (6.02)
Valve Guide Inside Diameter (Wear Limit), in (mm) ................ 0.240 (6.10)
Intake Valve Stem Outside Diameter (Standard), in (mm) ................ 0.235 (5.97)
Intake Valve Stem Outside Diameter (Wear Limit), in (mm) ................ 0.233 (5.92)
Exhaust Valve Stem Outside Diameter (Standard), in (mm) ................ 0.235 (5.97)
Exhaust Valve Stem Outside Diameter (Wear Limit), in (mm) ................ 0.233 (5.92)
Cam Lobes (Intake), in (mm) ................ 1.240 (31.49)
Cam Lobes (Exhaust), in (mm) ................ 1.240 (31.49)
| Piston and Piston Rings |
Piston Pin Outside Diameter (Standard), in (mm) ................ 0.7998 (20.31)
Piston Pin Outside Diameter (Wear Limit), in (mm) ................ 0.799 (20.29)
Piston Pin Bearing Inside Diameter (Standard), in (mm) ................ 0.8006 (20.33)
Piston Pin Bearing Inside Diameter (Wear Limit), in (mm) ................ 0.802 (20.37)
Top Ring End Gap (Standard), in (mm) ................ 0.006-0.009 (0.15-0.23)
Second Ring End Gap (Standard), in (mm) ................ 0.014-0.018 (0.35-0.45)
Oil Ring End Gap (Standard), in (mm) ................ 0.006-0.010 (0.15-0.25)
Piston Ring End Gap (Wear Limit), in (mm) ................ 0.030 (0.76)
Top Ring Side Clearance (Standard), in (mm) ................ 0.002-0.005 (0.05-0.12)
Second Ring Side Clearance (Standard), in (mm) ................ 0.002-0.005 (0.05-0.12)
Oil Ring Side Clearance (Standard), in (mm) ................ 0.002-0.005 (0.05-0.12)
Piston Ring Side Clearance (Wear Limit) ................ 0.007 (0.18)
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