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Inside a Pro Stock Motorcycle engine

Senior editor Kevin McKenna takes you inside a Pro Stock Motorcycle engine with this technical breakdown.
19 Jan 2019
Kevin McKenna, NHRA National Dragster Senior Editor
News
Pro Stock Motorcycle

Competitors in Pro Stock Motorcycle have a choice of two drastically different powerplants, both of which are capable of 6.7-second performances at speeds approaching 200 mph. Here is a detailed look at both the Suzuki inline four-cylinder engine and the 45-degree pushrod V-Twin that powers the Harley-Davidson, Buell, and EBR entries. 

PRO STOCK MOTORCYCLE – V TWIN PRO STOCK MOTORCYCLE – SUZUKI
(left side of header image) (right side of header image)
ENGINE BLOCK ENGINE BLOCK
Design: Naturally aspirated 160-cid V-Twin, two-valves per cylinder Design: Naturally-aspirated 1,850cc (113 cid) inline four cylinder, two-valves per cylinder based on an OE Suzuki GS 1150
Engine block: Billet 7075 aluminum, CNC machined Cylinder sleeves: Ductile iron
Bore: 5.125 inch (typical) Bore: 89.5mm (3.52 inch)
Stroke: 3.875 inch (typical) Stroke: 73.4mm (2.89 inch)
Maximum bore offset: 1.0 inches Bore centers: 95mm 1, 2 - 3, 4 (3.74inch)/120mm 2, 3 (4.72 inch)
Compression ratio: 14.5:1 Compression ratio: 16:1
Bank angle: 60 degree  
CRANKSHAFT CRANKSHAFT
Crankshaft: CNC-machined steel plain-rod bearings, roller mains Crankshaft: CNC-machined steel nine-piece pressed/welded together with roller bearing rods and mains
Rods: aluminum Rods: high-strength steel
Oiling system: Wet or dry sump permitted Oiling system: wet sump
Cylinder sleeves: Ductile iron  
CYLINDER HEADS CYLINDER HEAD
Cylinder heads: 6013 Billet-aluminum, CNC ported Cylinder heads: Cast aluminum, CNC ported
Intake valve size: 2.70 inches Intake valve size: 46-48mm (1.81 inch-1.89 inch)
Exhaust valve size: 2.00 inches Exhaust valve size: 38-40mm (1.49 inch-1.58 inch)
Valve covers: billet magnesium Valve covers: billet aluminum or cast magnesium
Camshaft: Roller camshaft made from tool steel, four individual cams, gear driven Camshaft: Roller chain driven, plain bearing, tool steel
Typical lift: 0.575-0.625 inch (x rocker ratio) Typical lift: 16mm-18mm (.63 inch-.70 inch)
Rocker arm ratio: 1.8 to 2.0 Lobe separation: 114-116 degrees
Lobe separation: 110-116 degrees Duration: 265-275 degrees (intake); 265-275 degrees (exhaust)
Duration: 285-290 degrees (intake); 300-305 degrees (exhaust) Lifter tappet: steel, DLC coated
Pushrods: 8-inch length, minimum per valve Valve springs: Steel, 195 pounds installed, 475 pounds max lift
Valve springs: Steel, 500-pounds installed, 1,400-pounds, max lift  
INTAKE AND IGNITION INDUCTION and IGNITON
Throttle body: Individual per cylinder/ billet aluminum with 3.25-inch blade Throttle body: Individual per cylinder sealed to a common plenum airbox; Lectron carburetors also an option and widely used
Intake runners: Billet magnesium or billet-aluminum, common plenum, breathing from sealed airbox Fuel Injectors: Limited to one per cylinder
Fuel Injectors: Limited to one per cylinder Ignition system: electronic fuel injection/ignition, two spark plugs per cylinder.
Ignition system: Electronic fuel injection/two spark plugs per cylinder Spark plugs: Denso Iridium
OTHER SPECS OTHER SPECS
Fuel: Sunoco SR-18, 118-octane leaded (mandatory) Fuel: Sunoco SR-18 118-octane leaded race gas (mandatory)
Fuel burned per run: 20-ounces, burnout to completion Fuel burned per run: 20-ounces, burnout to run completion
Spark plugs: Denso Iridium Headers: Stepped from 1.875 inch outside diameter to 2.25 inch four-into-one collector
Headers: stepped from 2.25 inch outside diameter to 3 inch Engine scavenge: 20-22 inHG
Engine scavenge: 20-22 inHG Engine redline: 14,000
Engine redline: 10,400 rpm Estimated horsepower and torque: 370 @13,600 rpm / 160 @ 10,000 rpm
Estimated horsepower and torque: 400 @ 9800/240 @ 7,000 Estimated weight: 185-pounds dry weight (engine and transmission as singular unit)
Estimated weight: 220-pounds (dry weight)