Professional Series™ (Single Cylinder)

World-class performance – time after time. With commercial-grade power, easy starting and quiet operation, the Professional Series riding mower engine delivers great results for your toughest jobs. And it keeps delivering, because this mower engine is built to last with our exclusive Advanced Debris Management System, chrome-plated exhaust valves and other durable features.

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Product Details

Professional Series™ rider mower engines

Single cylinder and V-twin engines offer the best of both worlds: world-class endurance and power.

Advanced Debris Management System

Keeps the engine clean by deflecting and ejecting grass and debris for a longer engine life.

Anti-Vibration System - AVS®

Provides a smoother ride and more comfort.

ReadyStart® Engine Starting System

No prime, no choke, no worries. Just pull for power.

Engine Type Single cylinder, 4-stroke, air cooled, OHV (Overhead Valve)
Gross Horsepower 15.5*
Model Number 31S7
Engine Displacement (cc) 500
Cylinder Cast Iron Sleeve
Bore (mm) 90.5
Stroke (mm) 77.8
Oil Capacity (L) 1.4
Dry Weight (kg) 29.5
Length (mm) 479
Width (mm) 411
Height (mm) 327
Consumer Warranty 2 Year Domestic Limited†
Commercial Warranty 1 Year Commercial Limited†

*Power levels are stated gross horsepower at 3600rpm per SAE J1940 as rated by Briggs & Stratton.
†See briggsandstratton.com for warranty details.

Engine Type Single cylinder, 4-stroke, air cooled, OHV (Overhead Valve)
Gross Horsepower 16.5*
Model Number 31S8
Engine Displacement (cc) 500
Cylinder Cast Iron Sleeve
Bore (mm) 90.5
Stroke (mm) 77.8
Oil Capacity (L) 1.4
Dry Weight (kg) 29.5
Length (mm) 479
Width (mm) 411
Height (mm) 327
Consumer Warranty 2 Year Domestic Limited†
Commercial Warranty 1 Year Commercial Limited†

*Power levels are stated gross horsepower at 3600rpm per SAE J1940 as rated by Briggs & Stratton.
†See briggsandstratton.com for warranty details.

Engine Type Single cylinder, 4-stroke, air cooled, OHV (Overhead Valve)
Gross Horsepower 17.5
Model Number 31S9
Engine Displacement (cc) 500
Cylinder Cast Iron Sleeve
Bore (mm) 90.5
Stroke (mm) 77.8
Oil Capacity (L) 1.4
Dry Weight (kg) 29.5
Length (mm) 479
Width (mm) 411
Height (mm) 327
Consumer Warranty 2 Year Domestic Limited†
Commercial Warranty 1 Year Commercial Limited†

*Power levels are stated gross horsepower at 3600rpm per SAE J1940 as rated by Briggs & Stratton.
†See briggsandstratton.com for warranty details.

Engine Type Single cylinder, 4-stroke, air cooled, OHV (Overhead Valve)
Gross Horsepower 18.5*
Model Number 33S7
Engine Displacement (cc) 540
Cylinder Cast Iron Sleeve
Bore (mm) 94
Stroke (mm) 77.8
Oil Capacity (L) 1.4
Dry Weight (kg) 29.5
Length (mm) 479
Width (mm) 411
Height (mm) 327
Consumer Warranty 2 Year Domestic Limited†
Commercial Warranty 1 Year Commercial Limited†

*Power levels are stated gross horsepower at 3600rpm per SAE J1940 as rated by Briggs & Stratton.
†See briggsandstratton.com for warranty details.

Engine Type Single cylinder, 4-stroke, air cooled, OHV (Overhead Valve)
Gross Horsepower 19*
Model Number 33S8
Engine Displacement (cc) 540
Cylinder Cast Iron Sleeve
Bore (mm) 94
Stroke (mm) 77.8
Oil Capacity (L) 1.4
Dry Weight (kg) 29.5
Length (mm) 479
Width (mm) 411
Height (mm) 327
Consumer Warranty 2 year Domestic Limited†
Commercial Warranty 1 Year Commercial Limited†

*Power levels are stated gross horsepower at 3600rpm per SAE J1940 as rated by Briggs & Stratton.
†See briggsandstratton.com for warranty details.

Engine Type V-Twin, 4-stroke, air cooled, OHV (Overhead Valve)
Gross Horsepower 18*
Model Number 40U7
Engine Displacement (cc) 656
Cylinder Cast Iron Sleeve
Bore (mm) 79.2
Stroke (mm) 73.4
Oil Capacity (L) 1.9
Dry Weight (kg) 37.9
Length (mm) 479
Width (mm) 393
Height (mm) 327
Consumer Warranty 2 Year Domestic Limited†
Commercial Warranty 1 Year Commercial Limited†

*Power levels are stated gross horsepower at 3600rpm per SAE J1940 as rated by Briggs & Stratton.
†See briggsandstratton.com for warranty details.

Engine Type V-Twin, 4-stroke, air cooled, OHV (Overhead Valve)
Gross Horsepower 20*
Model Number 40U8
Engine Displacement (cc) 656
Cylinder Cast Iron Sleeve
Bore (mm) 79.2
Stroke (mm) 73.4
Oil Capacity (L) 1.9
Dry Weight (kg) 37.6
Length (mm) 479
Width (mm) 393
Height (mm) 327
Consumer Warranty 2 Year Domestic Limited†
Commercial Warranty 1 Year Commercial Limited†

*Power levels are stated gross horsepower at 3600rpm per SAE J1940 as rated by Briggs & Stratton.
†See briggsandstratton.com for warranty details.