THE NEW HARLEY DAVIDSON REVOLUTION MAX 1250 ENGINE

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THE NEW HARLEY DAVIDSON REVOLUTION MAX 1250 ENGINE

Pan America 1250 and Pan America 1250 Special with new, liquid-cooled V2

The Harley-Davidson Pan America 1250 and Pan America 1250 Special are powered by the newly designed Revolution Max 1250 engine, a liquid-cooled V2 with powerful torque, powerful top performance and exciting revving. The company developed the engine to give the new adventure touring bikes a perfect drive: with smooth power delivery in the lower speed range and with sensitive control at low speeds, which is essential for off-road operation.

“Throughout our company’s history, Harley-Davidson has embraced technological advances without losing sight of our brand’s heritage. The decisive factor was always engines that offer real two-wheel fans everyday performance,” explains Harley-Davidson chief designer Alex Bozmoski. Revolution Max , redesigned from the ground up, is an engine that will power the Pan America models reliably, powerfully and with maximum efficiency.”

Development priorities in terms of performance and weight reduction form the background to central decisions in the architecture of the entire vehicle as well as the engine, in the selection of materials and the radical optimization of all components. Harley-Davidson integrated the engine as a supporting element in a central position in the chassis in order to achieve the lowest possible overall weight. Modern lightweight materials also contribute to the amazingly low power-to-weight ratio.

Revolution Max 1250

Displacement: 1,250 cm³

Bore x Stroke: 105.0mm x 72.0mm

Power: 112 kW (152 HP)/8,750 rpm

Max. torque: 128 Nm/6,750 rpm

Rotation speed: 9,500 rpm

Compression ratio: 13:1

Technical characteristics of the Revolution Max 1250

• V2 architecture

• A longitudinally installed V2 engine ensures a narrow design, the masses of which are grouped close to the center of gravity to ensure active handling, without affecting the space available for legs and feet.
• Thanks to its cylinder angle of 60 degrees, the engine is compact, but at the same time offers space between the cylinders for two throttle bodies in a flow-efficient downdraft arrangement for optimal performance.

• Weight-optimized design
A low engine weight also contributes to reducing the overall weight. Weight saving is the key to optimizing fuel consumption, acceleration, agility and braking performance.

• The finite element method and modern optimization processes in the development of the engine help to reduce the mass of cast and molded components, even in terms of the sheer amount of materials used. For example, as development progressed, more and more material was removed from the starter gear and camshaft drive gears in order to make these parts lighter.
• Weight-saving design features also include one-piece light alloy cylinders with a tread coating of nickel and silicon carbide.
• The valve and primary drive covers of the new models are made of a lightweight magnesium alloy.

• Drive as a load-bearing chassis component

The Revolution Max 1250 is also integrated into the chassis as a supporting part.

• The engine fulfills two functions: It serves as a drive and is also a structural element of the chassis.
• The lack of a classic main frame is the key to giving the chassis both a particularly low weight and extremely high torsional rigidity.
• A front frame element, a middle segment and the rear frame are bolted directly to the engine.
• The engine is designed to be particularly robust and rigid so that it can effectively fulfill its function as a chassis component.
• The advantage for the driver is optimized driving characteristics thanks to significant weight savings, high torsional rigidity and masses that are tightly centralized around the center of gravity.

• Liquid cooling

Strong waste heat affects both longevity and driver comfort. Liquid cooling ensures stable, controllable engine and oil temperatures for consistent performance across a wide range of environmental conditions and driving situations.

• Engine components with tight tolerances contribute to high drive performance. Tight tolerances, in turn, require efficient temperature control to limit thermal expansion and contraction of metal parts.
• The liquid cooling also supports the exhaust sound by dampening the mechanical noise from inside the engine.
• The waste heat from the engine oil is also dissipated by the liquid cooling, which ensures optimal lubrication and long oil change intervals even under the toughest operating conditions.
• When designing the cooling system, the focus was on attractive appearance, easy maintenance and robustness.
• The internal coolant pump is equipped with high-performance bearings and seals for maximum durability.
• To save weight and width, the coolant lines are integrated directly into the complex cast alternator cover.
• The coolant drain plug is well protected from damage during off-road use in a recess in the area of ​​a footrest.

• Crank pin offset

The two crank pins are arranged on the crankshaft at 30 degrees to each other. Harley-Davidson was able to draw on its extensive experience in flat track racing when optimizing the Revolution Max 1250.

• The crank pin offset of 30 degrees gives the engine the firing order of a 90-degree V engine for smooth running, especially in the upper speed range.
• This crankshaft design requires a lateral cylinder offset. For ergonomics, Harley-Davidson moved the rear cylinder slightly to the left.
• The firing order provides more traction in certain off-road driving situations, giving the driver improved control over the machine.
• At the same time, the firing order contributes to a characteristic exhaust sound.

• Light alloy forged pistons

• The piston crowns are milled to ensure a precise compression ratio. A compression ratio of 13:1 supports high torque in all speed ranges. The high compression is made possible by the most modern knock sensors. To achieve its rated power, the engine requires premium 91 octane gasoline. However, when the power is reduced, it also runs on fuel with a lower octane number and is protected from harmful knocking by modern sensor technology. Of course, petrol fuels with higher levels of bioethanol (E 10) can also be used.
• Thanks to the chamfered piston skirt, no piston ring clamping mechanism is required for assembly.
• The piston skirt has a coating to reduce frictional resistance.
• Piston rings with low preload further reduce friction and contribute to high power output.
• The top piston ring is anodized for increased longevity.
• Spray oil nozzles directed from below onto the piston crowns help dissipate the combustion heat.

• Four-valve cylinder heads

• Cylinder heads with four valves each allow larger valve cross sections.
• An optimized gas flow through the combustion chamber ensures optimal power development with powerful torque in the lower and middle speed ranges as well as smooth onset of peak power.
• The exhaust valves contain a sodium fill to aid heat dissipation.
• Highly developed casting processes allow the oil lines to be integrated directly into the cylinder heads and at the same time contribute to weight savings by optimizing the wall thicknesses.
• The cylinder heads are made from light metal alloy 354. Since they also form suspension points of the chassis, they have a well-defined flexibility in the area of ​​the corresponding flanges, while the area of ​​the combustion chamber is very rigid. Harley-Davidson achieves this, among other things, through targeted heat treatment.

• Two overhead camshafts per cylinder (DOHC)

The Revolution Max 1250 works with separate intake and exhaust camshafts for both cylinders.

• The DOHC design, with its low inertia, promotes high revving and maximum speed. This also increases the performance output.
• It also allows independent variable intake and exhaust valve timing (VVT), each optimized for the front and rear cylinders, and thus a wider usable speed range.
• All valve elevation curves are optimized for the most advantageous performance characteristics possible.
• The bearing journal of the camshaft on the drive side is integrated into the drive gear. This design makes it possible to dismantle the camshaft for maintenance or tuning purposes without dismantling the camshaft drive.
• The timing chain guides and gears are optimized to be as light as possible. Design features of the internal timing chain tensioner minimize noise when starting.

• Hydraulic valve clearance compensation

• The valves on the Revolution Max 1250 are operated via roller rocker arms with hydraulic valve clearance compensation.
• This design allows constant contact between the valves and their actuators despite the thermal expansion of the individual components.
• Thanks to the hydraulic valve clearance compensation, the valve train is maintenance-free, saving the owner time and money. There is no mechanical adjustment device.
• At the same time, this design reduces the noise generated by the valve train, especially during cold starts.
• The hydraulic valve clearance compensation ensures constant pressure on the valve stem. This allows for more aggressive valve lift curves for more power.

• Variable valve timing (VVT)

The Revolution Max 1250 features electronically controlled Variable Valve Timing (VVT) on the intake and exhaust camshafts.

• The variable valve timing has a control range of 40 degrees on the intake and exhaust camshafts.
• Compared to an engine with fixed valve timing, VVT ensures a wider usable speed range with increased efficiency and optimized torque characteristics. The engine offers more dynamic acceleration from low revs, but at the same time is extremely easy to rev with high peak performance.
• VVT simultaneously reduces consumption and thus increases the range.
• The electro-hydraulic phaser is located between the camshaft drive gear and the camshaft.
• When the engine is switched off, the variable valve timing retards the intake camshafts as far as possible and retards the exhaust camshafts in the opposite direction to reduce compression and thus make the next starting process easier.
• The camshaft position sensors are located in the valve covers.

• Double ignition

The new Revolution Max 1250 has two spark plugs per cylinder.

• The double ignition contributes to optimized combustion despite the large cylinder bore.
• Instead of traditional spark plugs, the Revolution Max 1250 uses spark plugs with two side ground electrodes.

• Downdraft throttle body

Two separate throttle bodies between the cylinders in a downdraft arrangement ensure minimal turbulence and the greatest possible gas throughput.

• The highest possible inlet volume flow promotes high peak performance.
• Fuel injection can be optimized separately for each cylinder to improve fuel consumption and range.
• The central position of the throttle body also allows the airbox with a volume of eleven liters to be ideally installed above the engine. Such a large-volume airbox is crucial for optimal power development.
• The shape of the airbox allows the use of specially tailored separate intake funnels for both throttle bodies. These use the inertia of the incoming air to increase the degree of filling of the cylinders and thus the performance.
• The airbox is made of glass fiber reinforced nylon. Integrated ribs on the inside help suppress unwanted resonances and dampen intake noise. Its forward-facing intake directs the intake noise away from the driver, helping to enhance the exhaust note.
• The circular base of the washable conical air filter element forms an ideal seal for the airbox.

• Robust lubrication system

The lubrication system is designed to function reliably even under difficult operating conditions.

• The new engine has dry sump lubrication, the oil reservoir of which is integrated into the engine housing below all moving parts. This design eliminates churning losses in favor of increased engine performance.
• Three separate suction pumps suck the engine oil from the crankcase as well as the alternator and clutch tunnels.
• A baffle plate also prevents the clutch from introducing too much air into the engine oil, which could affect delivery performance.
• A large oil strainer in front of the feed pump filters particles from the oil flow to ensure a long engine life.
• The oil pump is designed to create negative pressure in the crankcase. Harley-Davidson uses this effect to further reduce internal friction, as this allows piston rings to be used with lower preload.
• The oil is directed through the center of the crankshaft to the lubrication points of the main bearings and connecting rod bearings. This design allows a comparatively low oil pressure in the range of 4.1 to 4.8 bar and thus reduces power losses at high speeds.

• Drive with complete mass balancing

Internal balancer shafts almost completely eliminate engine vibrations for increased driving comfort and durability.

• Primary balancer shaft: The helical chain-driven balancer shaft in the crankcase balances the first-order inertial forces caused by the crank pins, pistons and connecting rods, as well as the lateral vibration moment caused by the lateral cylinder offset.
• Secondary Balancer Shaft: A small balancer shaft between the front cylinder head camshafts complements the primary balancer shaft to further reduce vibration levels.
• The balance shafts are tuned to allow just enough vibration so that the motorcycle feels alive.
• The balancer shafts contribute to weight savings and high power output, as numerous engine components no longer have to be designed to withstand the vibration load caused by vibrations.

• Clutch and gearbox

The engine and six-speed gearbox on the new Revolution Max 1250 are housed in a common housing.

• The clutch is operated via a large cross-section Bowden cable for smooth operation with consistent separation and low friction.
• A clutch support function reduces the operating forces on the clutch lever without affecting the smooth transmission of the high engine power.
• The clutch has eight friction discs for reliable power transmission in every driving situation.
• The anti-hopping function prevents both engine over-revving and rear wheel stalling when downshifting.
• The entire primary drive is designed to minimize noise and vibration. Its specially designed helical gearing reduces both load change jerking and mechanical noise.
• Balance springs in the primary gear smooth torque peaks from the crankshaft before they enter the transmission to ensure consistent torque delivery.
• A roller-bearing shift drum and Teflon-coated shift shaft support bushings minimize friction losses in the shifting mechanism of the six-speed transmission and ensure a precise shifting feel.
• The internal components of the gearshift are durable, but at the same time weight-optimized to achieve smooth gear changes and powerful acceleration and to avoid loss of power when shifting.
• The gear tunnel, which is continuously evacuated by the dry sump lubrication, ensures minimal power losses and reduced consumption because the gears do not constantly roll in the oil bath.