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Whether you’re a professional engine builder, mechanic or manufacturer, or a car enthusiast who loves engines, racing cars and fast cars, Engine Builder has something for you. Our print magazines provide technical details on everything you need to know about the engine industry and its various markets, while our newsletter options keep you up to date with the latest news and products, technical information and industry performance. However, you can get all this only by subscription. Subscribe now to receive monthly print and/or electronic editions of Engine Builders Magazine, as well as our Weekly Engine Builders Newsletter, Weekly Engine Newsletter or Weekly Diesel Newsletter, straight to your inbox. You’ll be covered in horsepower in no time!
The Harley-Davidson Revolution Max 1250 engine is assembled at powertrain company Pilgrim Road’s plant in Wisconsin. The V-Twin has a displacement of 1250 cc. cm, bore and stroke 4.13 inches (105 mm) x 2.83 inches (72 mm) and is capable of 150 horsepower and 94 lb-ft of torque. The maximum torque is 9500 and the compression ratio is 13:1.
Throughout its history, Harley-Davidson has used technological developments, respecting the heritage of its brand, to provide real performance for real riders. One of Harley’s latest cutting-edge design achievements is the Revolution Max 1250 engine, an all-new liquid-cooled V-twin engine used in the Pan America 1250 and Pan America 1250 Special models.
Engineered for agility and appeal, the Revolution Max 1250 engine has a wide powerband for a redline power boost. The V-Twin engine has been specifically tuned to provide ideal power characteristics for the Pan America 1250 models, with an emphasis on smooth low-end torque delivery and low-end throttle control for off-road riding.
A focus on performance and weight reduction drives vehicle and engine architecture, material selection and active optimization of component design. To minimize the overall weight of the motorcycle, the engine is integrated into the Pan Am model as the main chassis component. The use of lightweight materials helps achieve an ideal power-to-weight ratio.
The Revolution Max 1250 engine is assembled at Harley-Davidson Pilgrim Road Powertrain Operations in Wisconsin. The V-Twin has a displacement of 1250 cc. cm, bore and stroke 4.13 inches (105 mm) x 2.83 inches (72 mm) and is capable of 150 horsepower and 94 lb-ft of torque. The maximum torque is 9500 and the compression ratio is 13:1.
The V-Twin engine design provides a narrow transmission profile, concentrates mass for improved balance and handling, and provides the rider with ample legroom. The 60-degree V-angle of the cylinders keeps the engine compact while providing space for downdraft dual throttle bodies between the cylinders to maximize airflow and improve performance.
Reducing the weight of the transmission helps reduce the weight of the motorcycle, which improves efficiency, acceleration, handling and braking. The use of Finite Element Analysis (FEA) and advanced design optimization techniques in the engine design phase minimizes material mass in cast and molded parts. For example, as the design progressed, material was removed from the starter gear and camshaft drive gear to reduce the weight of these components. The one-piece aluminum cylinder with nickel-silicon carbide surface electroplating is a lightweight design feature, as well as a lightweight magnesium alloy rocker cover, camshaft cover and main cover.
According to Harley-Davidson Chief Engineer Alex Bozmosky, the Revolution Max 1250′s drivetrain is a structural component of the motorcycle’s chassis. Therefore, the engine has two functions – to provide power and as a structural element of the chassis. The elimination of the traditional frame significantly reduces the weight of the motorcycle and provides a very strong chassis. The front frame members, middle frame members and rear frame are bolted directly to the transmission. Riders achieve optimal performance through significant weight savings, a rigid chassis and mass centralization.
In a V-Twin engine, heat is the enemy of durability and rider comfort, so the liquid-cooled engine maintains a stable and controlled engine and oil temperature for consistent performance. Because metal components expand and contract less, tight component tolerances can be achieved by controlling engine temperature, resulting in improved transmission performance.
In addition, the perfect engine sound and exciting exhaust note can dominate as noise from the engine’s internal sources is reduced by liquid cooling. The engine oil is also liquid-cooled to ensure the performance and durability of the engine oil in harsh conditions.
The coolant pump is built into high performance bearings and seals for extended life, and coolant passages are integrated into the complex casting of the stator cover to reduce transmission weight and width.
Inside, the Revolution Max 1250 has two crankpins offset by 30 degrees. Harley-Davidson used its extensive cross-country racing experience to understand the Revolution Max 1250′s power pulse rhythm. degree sequencing can improve traction in certain off-road driving situations.
Attached to the crank and connecting rods are forged aluminum pistons with a compression ratio of 13:1, which increase the engine’s torque at all speeds. Advanced knock detection sensors make this high compression ratio possible. The engine will require 91 octane fuel for maximum power, but will run on low octane fuel and will prevent explosions thanks to knock sensor technology.
The bottom of the piston is chamfered so no ring compression tool is required for installation. The piston skirt has a low friction coating and low tension piston rings reduce friction for improved performance. The top ring linings are anodized for durability, and the oil-cooling jets point to the bottom of the piston to help dissipate the heat of combustion.
In addition, the V-Twin engine uses four-valve cylinder heads (two intake and two exhaust) to provide the largest possible valve area. This ensures strong low-end torque and a smooth transition to peak power as the airflow through the combustion chamber is optimized to meet the required performance and displacement requirements.
Exhaust valve filled with sodium for better heat dissipation. Suspended oil passages in the head are achieved through sophisticated casting technology, and weight is reduced due to the minimum wall thickness of the head.
The cylinder head is cast from high strength 354 aluminum alloy. Because the heads act as chassis attachment points, they are designed to be flexible at that attachment point but rigid over the combustion chamber. This is partly achieved through targeted heat treatment.
The cylinder head also has independent intake and exhaust camshafts for each cylinder. The DOHC design promotes higher RPM performance by reducing valve train inertia, resulting in higher peak power. The DOHC design also provides independent variable valve timing (VVT) on the intake and exhaust cams, optimized for the front and rear cylinders for a wider powerband.
Select a specific cam profile to get the most desired performance. The drive side camshaft bearing journal is part of the drive sprocket, designed to allow removal of the camshaft for service or future performance upgrades without removing the camshaft drive.
To close the valve train on the Revolution Max 1250, Harley used a roller pin valve actuation with hydraulic lash adjusters. This design ensures that the valve and valve actuator (pin) remain in constant contact as the engine temperature changes. Hydraulic lash adjusters make the valve train maintenance-free, saving owners time and money. This design maintains constant pressure on the valve stem, resulting in a more aggressive camshaft profile for improved performance.
The air flow in the engine is aided by dual downdraft throttles positioned between the cylinders and positioned to create minimal turbulence and airflow resistance. Fuel delivery can be optimized individually for each cylinder, improving economy and range. The central location of the throttle body allows the 11-litre air box to sit perfectly above the engine. Air chamber capacity is optimized for engine performance.
The shape of the airbox allows for a tuned speed stack on each throttle body, using inertia to force more air mass into the combustion chamber, increasing power output. The airbox is made from glass-filled nylon with built-in internal fins to help dampen resonance and dampen intake noise. Forward-facing intake ports deflect intake noise away from the driver. Eliminating intake noise allows the perfect exhaust sound to dominate.
Good engine performance is ensured by a reliable dry sump lubrication system with an oil reservoir built into the crankcase casting. Triple oil drain pumps drain excess oil from three engine chambers (crankcase, stator chamber and clutch chamber). Riders get the best performance because parasitic power loss is reduced because the engine’s internal components don’t have to spin through excess oil.
The windshield prevents the clutch from charging the engine oil, which can reduce oil supply. By feeding oil through the center of the crankshaft to the main and connecting rod bearings, this design provides low oil pressure (60-70 psi), which reduces parasitic power loss at high rpm.
The ride comfort of the Pan America 1250 is ensured by an internal balancer that eliminates much of the engine vibration, improving rider comfort and extending the vehicle’s durability. The main balancer, located in the crankcase, controls the main vibrations created by the crankpin, piston and connecting rod, as well as the “rolling clutch” or left-right imbalance caused by a misaligned cylinder. An auxiliary balancer in the front cylinder head between the camshafts complements the main balancer to further reduce vibration.
Finally, the Revolution Max is a unified drivetrain, which means the engine and six-speed gearbox are housed in a common body. The clutch is equipped with eight friction discs designed to provide constant engagement at maximum torque throughout the life of the clutch. Compensating springs in the final drive smooth out crankshaft torque impulses before they reach the gearbox, ensuring consistent torque transmission.
Overall, the Revolution Max 1250 V-Twin is a great example of why Harley-Davidson motorcycles are still in such demand.
This week’s engine sponsors are PennGrade Motor Oil, Elring-Das Original and Scat Crankshafts. If you have an engine you’d like to highlight in this series, please email Engine Builder editor Greg Jones [email protected]
Post time: Nov-15-2022