_______________________________________________________________________________________

Briggs and Stratton 31F707 Engine

General Technical Data

Briggs and Stratton 31F707 Engine Specifications

Engine Model ............ Briggs and Stratton 31F707
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) ............ 17.0 (12.7)
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 (paper and foam)
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 ............ Pulse type
Governor Type ............ Mechanical
Fuel Type ............ Gasoline

Briggs and Stratton 31F707 Maintenance Data

Cylinder Block and Valves

Cylinder Bore Inside Diameter (Maximum), in (mm) ............ 3.567 (90.60)
Cylinder Head (Max. Out of Flatness), in (mm) ............ 0.004 (0.10)
Valve Clearance (Intake), in (mm) ............ 0.003-0.005 (0.08-0.13)
Valve Clearance (Exhaust), in (mm) ............ 0.005-0.007 (0.13-0.18)

Engine Oil and Filters

Engine Oil Type (Summer) ............ SAE 30, 10W-30
Engine Oil Type (Winter) ............ SAE 5W-30
API Service Classifications ............ SF, SG, SH, SJ or higher
Oil Capacity, qts (L) ............ 1.51 (1.42)
Oil Filter Part Number ............ 492932S
Air Filter Element Part Number ............ 794422

Ignition System

Spark Plug Type ............ Champion RC12YC
Spark Plug Gap, in (mm) ............ 0.03 (0.76)
Armature Air Gap, in (mm) ............ 0.010-0.014 (0.25-0.36)
Spark Plug Torque, Nm (lb-ft) ............ 20 (14.8)

Service Intervals

Service Air Filter Pre-Cleaner ............ Every 25 hours
Clean Air Filter ............ Every 25 hours
Change Engine Oil ............ Every 50 hours
Check and Adjust Spark Plug ............ Every 50 hours
Change Engine Oil Filter ............ Every 100 hours
Replace Air Filter ............ Every 100 hours
Replace Inline Fuel Filter ............ Every 100 hours
Check Carburetor Adjustment ............ Every 100 hours
Replace Spark Plug ............ Every 100 hours
Check Valve Clearance ............ Every 200 hours

Briggs and Stratton 31F707 Service Specifications

Cylinder Block

Cylinder Bore I.D. (Standard), in (mm) ............ 3.563 (90.50)
Cylinder Bore I.D. (Maximum), in (mm) ............ 3.567 (90.60)
Cylinder Bore (Out-Of-Round), in (mm) ............ 0.0015 (0.04)
Main Bearing Bore Dia. (Cylinder Block), in (mm) ............ 1.3795 (35.04)
Main Bearing Bore Dia. (Crankcase Cover), in (mm) ............ 1.063 (27.00)
Camshaft Bearing Bore Dia. (Cylinder Block), in (mm) ............ 0.5011 (15.88)
Camshaft Bearing Bore Dia. (Crankcase Cover), in (mm) ............ 0.501 (12.72)
Crank Pin Journal O.D. (Standard), in (mm) ............ 1.4982 (38.05)
Crank Pin Journal O.D. (Wear Limit), in (mm) ............ 1.497 (31.02)
Crankshaft Journal O.D. (Magneto Side), in (mm) ............ 1.3775 (35.00)
Crankshaft Journal O.D. (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 O.D. (Magneto Side), in (mm) ............ 0.499 (12.67)
Camshaft Journal O.D. (PTO Side), in (mm) ............ 0.499 (12.67)
Connecting Rod Big End I.D. (Standard), in (mm) ............ 1.2505 (31.76)
Connecting Rod Big End I.D. (Wear Limit), in (mm) ............ 1.2525 (31.81)
Connecting Rod Small End I.D. (Standard), in (mm) ............ 0.8006 (20.33)
Connecting Rod Small End I.D. (Wear Limit), in (mm) ............ 0.802 (20.37)
Counterweight Bearings Dia. (Standard), in (mm) ............ 2.207 (56.05)
Counterweight Bearings Dia. (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 I.D. (Standard), in (mm) ............ 0.237 (6.02)
Valve Guide I.D. (Wear Limit), in (mm) ............ 0.240 (6.10)
Intake Valve Stem O.D. (Standard), in (mm) ............ 0.235 (5.97)
Intake Valve Stem O.D. (Wear Limit), in (mm) ............ 0.233 (5.92)
Exhaust Valve Stem O.D. (Standard), in (mm) ............ 0.235 (5.97)
Exhaust Valve Stem O.D. (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 O.D. (Standard), in (mm) ............ 0.7998 (20.31)
Piston Pin O.D. (Wear Limit), in (mm) ............ 0.799 (20.29)
Piston Pin Bearing I.D. (Standard), in (mm) ............ 0.8006 (20.33)
Piston Pin Bearing I.D. (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)

Briggs and Stratton 31F707 Tightening Torque Specs

Air Cleaner Base, Lb-ft (Nm) ............ 4.4 (6.0)
Alternator, Lb-ft (Nm) ............ 1.5 (2.0)
Armature, Lb-ft (Nm) ............ 2.2 (3.0)
Blower Housings, Lb-ft (Nm) ............ 7.4 (10.0)
Blower Housing Brackets, Lb-ft (Nm) ............ 7.4 (10.0)
Breather, Lb-ft (Nm) ............ 2.2 (3.0)
Carburetor to Intake Manifold, Lb-ft (Nm) ............ 5.9 (8.0)
Carburetor Solenoid, Lb-ft (Nm) ............ 3.7 (5.0)
Connecting Rod, Lb-ft (Nm) ............ 12.6 (17.0)
Control Bracket, Lb-ft (Nm) ............ 2.2 (3.0)
Crankcase Sump, Lb-ft (Nm) ............ 18.5 (25.0)
Cylinder Head, Lb-ft (Nm) ............ 18.5 (25.0)
Cylinder Shield, Lb-ft (Nm) ............ 3.7 (5.0)
Exhaust Manifold/Adapter, Lb-ft (Nm) ............ 14.1 (19.0)
Flywheel Nut, Lb-ft (Nm) ............ 100.0 (135.0)
Flywheel Fan, Lb-ft (Nm) ............ 11.9 (16.0)
Fuel Pump, Lb-ft (Nm) ............ 7.4 (10.0)
Governor Lever Nut, Lb-ft (Nm) ............ 3.7 (5.0)
Intake Manifold to Cylinder Head, Lb-ft (Nm) ............ 7.4 (10.0)
Muffler, Lb-ft (Nm) ............ 7.4 (10.0)
Oil Drain Plug, Lb-ft (Nm) ............ 8.1 (11.0)
Oil Fill Tube, Lb-ft (Nm) ............ 7.4 (10.0)
Oil Pump Cover, Lb-ft (Nm) ............ 7.4 (10.0)
Regulator/Rectifier, Lb-ft (Nm) ............ 3.7 (5.0)
Rewind Starter, Lb-ft (Nm) ............ 2.2 (3.0)
Rocker Ball Set Screw or Nut, Lb-ft (Nm) ............ 3.7 (5.0)
Spark Plug, Lb-ft (Nm) ............ 14.8 (20.0)
Starter Motor, Lb-ft (Nm) ............ 11.9 (16.0)
Rocker Cover, Lb-ft (Nm) ............ 5.2 (7.0)