HARLEY-DAVIDSON REVOLUTION MAX 1250 ENGINE IS TUNED FOR ADVENTURE

Revolution® Max 1250 Engine

Displacement: 1250cc

Bore x Stroke: 4.13 in. (105 mm) x 2.83 in (72 mm)

Horsepower: 150hp

Peak Torque: 94 ft. lbs.

Peak RPM: 9500

Compression Ratio: 13:1

Liquid Cooling

Heat is an enemy of both durability and rider comfort. Liquid cooling the engine maintains a stable and controllable engine and oil temperature for consistent performance in changing environmental and riding situations.

• Powertrain performance is enhanced by tight component tolerances that can be achieved when engine temperature is controlled (there is less expansion and contraction of metal parts).
• Desirable engine sounds – a stirring exhaust tone – can predominate because noise from internal engine sources is reduced by liquid cooling.
• The engine oil is also liquid cooled, which ensures that engine oil performance and durability will be maintained in challenging conditions.
• The cooling system is designed to be esthetically pleasing, easy to service and rugged.
• The coolant pump is internal and features high-performance bearings and seals for extended service life.
• Coolant passages are integrated into a complex stator cover casting to save weight and reduce powertrain width.
• A coolant drain plug is recessed and guarded by a foot peg to limit vulnerability to damage in off-road riding situations.

Offset Connecting Rod Journals

The two crankshaft connecting rod journals are offset by 30 degrees. Harley-Davidson leveraged its extensive experience in flat track racing to help inform the cadence of Revolution® Max 1250 engine power pulses.

• The 30-degree offset creates a 90-degree firing order that produces a smooth power delivery, especially at higher RPM.
• The cylinders are offset slightly to accommodate the crankshaft design, with the rear cylinder positioned to the rider’s left on the crankcase, a choice made to enhance ergonomics.
• The rider may gain control and confidence because the power pulses of a 90-degree firing order may improve traction in some off-road riding situations.
• The 90-degree firing order produces a stirring exhaust beat.

Double Overhead Camshafts (DOHC)

The Revolution Max 1250 engine is equipped with separate intake and exhaust camshafts for each cylinder.

• The DOHC design facilitates higher-RPM operation by reducing valve train inertia, which produces higher peak horsepower.
• The DOHC design permits independent Variable Valve Timing (VVT) on the intake and exhaust cam, optimized for the front and rear cylinder, to broaden the powerband.
• Specific cam profiles are selected to produce the most-desirable performance characteristics.
• The drive-side camshaft bearing journal is part of the drive sprocket, a design that makes it possible to remove the camshaft for service or a future performance upgrade without disassembling the camshaft drive.
• The camshaft drive chain guides and sprockets have been optimized to reduce as much mass as possible. The chain tensioner is internally mounted and incorporates design features to minimize start-up clatter.
   

Hydraulic Lash Adjusters

• The Revolution® Max 1250 engine features roller-finger valve actuation with hydraulic lash adjusters.
• This design ensures that the valves and valve actuators (“fingers”) are in constant contact as engine heat changes.
• The hydraulic lash adjusters make the valve train maintenance-free, saving the owner time and cost – there is no mechanical adjuster.
• This design realizes a reduction in undesirable valve train noise, especially on cold starts.
• This design maintains consistent pressure on the valve stem, which facilitates more-aggressive camshaft profiles which can boost performance.

Dual Down-Draft Throttle Bodies

Separate throttle bodies are located between the cylinders, positioned to create minimal turbulence and impedance to air flow.

• High-velocity air flow into the combustion chamber is optimized for improved performance.
• Fuel delivery can be optimized individually for each cylinder, which can improve economy and range.
• The central location of the throttle bodies permits the ideal position of an 11-liter airbox over the engine. Airbox capacity is optimized for engine performance.
• The airbox is shaped to permit use of tuned velocity stacks over each throttle body that utilize inertia to pack more air mass into the combustion chamber, which can increase power output.
• The airbox is formed of glass-filled nylon with integrated internal ribs that help quell resonance and muffle intake noise. A forward-facing intake snorkel directs intake noise away from the rider. Silencing intake noise permits desirable exhaust tone to predominate.
• The circular base of the washable conical air filter provides an optimal seal to the airbox.

Robust Oiling System

The engine oiling system is scaled to perform well in challenging conditions.

• The engine features a dry sump oiling system, with the oil reservoir (or sump) incorporated into the crankcase casting below all rotating parts. This increases performance by reducing the parasitic power loss that can occur when a rotating part must pass through an oil bath.
• Triple oil scavenge pumps evacuate excess oil from three engine cavities – crankcase, stator cavity and clutch cavity. The rider gains optimal performance as parasitic power loss is reduced because internal engine components do not have to rotate through excess oil.
• A windage tray prevents the clutch from aerating engine oil, which could degrade oil delivery.
• The oil feed pump is fitted with a large-capacity screen able to filter debris for the lifespan of the motorcycle.
• The oil pump is designed to pull vacuum in the crankcase, which can further reduce internal engine friction because lighter piston ring pressure is required to minimize combustion blow-by.
• Oil delivery to main bearings and connecting rod bearings is delivered through the center of the crankshaft, a design that enables low oil pressure (60-70 psi) that reduces parasitic power loss at high RPM.

Clutch and Transmission

The Revolution® Max is a unitized powertrain, meaning that the engine and six-speed transmission are housed in a common case.

• The clutch is mechanically actuated with a large-diameter cable for smooth, consistent  disengagement and minimal drag.
• The clutch assist function offers a lighter feel at the clutch lever while maintaining the ability to transmit full torque and power to the transmission.
• The clutch features eight friction plates designed to provide consistent engagement at maximum torque throughout the life of the clutch.
• A clutch slipper function enables the rider to downshift without over-speeding the engine or slipping or hopping the rear wheel.
• To minimize NVH (noise vibration harshness) the primary gear assembly was designed to achieve the optimal balance of sound quality and performance. A custom-designed scissor gear reduces both backlash and gear meshing noise.
• Compensation springs in the primary gear smooth out torque pulses from the crankshaft before they reach the transmission, providing consistent torque delivery.
• The six-speed transmission shift system features roller bearings to support the shift drum and Teflon-coated shift shaft support bushings to minimize frictional losses and optimize shift quality.
• Internal shift components are durable but also as light as possible to improve shift quality and acceleration by minimizing power losses during shift events.
• The semi-dry transmission cavity reduces parasitic power loss and increases fuel economy for the customer because gears are not churning through oil.