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Briggs and Stratton 31P977 Specifications
| Engine Model: Briggs and Stratton 31P977 |
| Engine Type: 4-cycle single cylinder OHV vertical shaft gasoline engine |
| Total Displacement: 30.6 cu.in (501 cc) |
| Rated Engine Power: 20 Hp (14.9 kW) at 3600 rpm |
| Fuel System: Float type carburetor with fixed main jet |
Engine Model ................ Briggs and Stratton 31P977
Engine Type ................ 4-cycle single cylinder OHV vertical shaft air-cooled gasoline engine
Number of Cylinders ................ 1
Displacement, cu.in (cc) ................ 30.6 (501)
Cylinder Bore, in (mm) ................ 3.56 (91.0)
Piston Stroke, in (mm) ................ 3.06 (78.0)
Rated Engine Power, hp (kW) ................ 20.0 (14.9)
Rated Engine Speed, rpm ................ 3600
Idle Speed, rpm ................ 1750
Cylinder Bore Type ................ Cast iron sleeve
Lubrication System ................ Full pressure
Air Cleaner ................ Paper cartridge
Cooling System ................ Forced air
Ignition System ................ Electronic
Starting System ................ Electric starter
Electrical System Rating, Volts ................ 12
Charging System Rating, Amps ................ 9
Fuel System Type ................ Carburetor
Carburetor Type ................ Float
Fuel Pump ................ Pulse type
Governor Type ................ Mechanical
Fuel Type ................ Gasoline
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 (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 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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