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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
Feature
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 TWINPRO STOCK MOTORCYCLE – SUZUKI
(left side of header image)(right side of header image)
ENGINE BLOCKENGINE BLOCK
Design: Naturally aspirated 160-cid V-Twin, two-valves per cylinderDesign: 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 machinedCylinder 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 inchesBore centers: 95mm 1, 2 - 3, 4 (3.74inch)/120mm 2, 3 (4.72 inch)
Compression ratio: 14.5:1Compression ratio: 16:1
Bank angle: 60 degree 
CRANKSHAFTCRANKSHAFT
Crankshaft: CNC-machined steel plain-rod bearings, roller mainsCrankshaft: CNC-machined steel nine-piece pressed/welded together with roller bearing rods and mains
Rods: aluminumRods: high-strength steel
Oiling system: Wet or dry sump permittedOiling system: wet sump
Cylinder sleeves: Ductile iron 
CYLINDER HEADSCYLINDER HEAD
Cylinder heads: 6013 Billet-aluminum, CNC portedCylinder heads: Cast aluminum, CNC ported
Intake valve size: 2.70 inchesIntake valve size: 46-48mm (1.81 inch-1.89 inch)
Exhaust valve size: 2.00 inchesExhaust valve size: 38-40mm (1.49 inch-1.58 inch)
Valve covers: billet magnesiumValve covers: billet aluminum or cast magnesium
Camshaft: Roller camshaft made from tool steel, four individual cams, gear drivenCamshaft: 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 2.0Lobe separation: 114-116 degrees
Lobe separation: 110-116 degreesDuration: 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 valveValve springs: Steel, 195 pounds installed, 475 pounds max lift
Valve springs: Steel, 500-pounds installed, 1,400-pounds, max lift 
INTAKE AND IGNITIONINDUCTION and IGNITON
Throttle body: Individual per cylinder/ billet aluminum with 3.25-inch bladeThrottle 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 airboxFuel Injectors: Limited to one per cylinder
Fuel Injectors: Limited to one per cylinderIgnition system: electronic fuel injection/ignition, two spark plugs per cylinder.
Ignition system: Electronic fuel injection/two spark plugs per cylinderSpark plugs: Denso Iridium
OTHER SPECSOTHER 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 completionFuel burned per run: 20-ounces, burnout to run completion
Spark plugs: Denso IridiumHeaders: 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 inchEngine scavenge: 20-22 inHG
Engine scavenge: 20-22 inHGEngine redline: 14,000
Engine redline: 10,400 rpmEstimated horsepower and torque: 370 @13,600 rpm / 160 @ 10,000 rpm
Estimated horsepower and torque: 400 @ 9800/240 @ 7,000Estimated weight: 185-pounds dry weight (engine and transmission as singular unit)
Estimated weight: 220-pounds (dry weight)