A modification package designed to increase the displacement of a Harley-Davidson motorcycle engine to 107 cubic inches. This typically involves replacing the cylinders and pistons with larger-diameter components.
Increasing engine displacement generally leads to enhanced horsepower and torque. This results in improved acceleration and overall performance, particularly noticeable during passing maneuvers and when carrying heavy loads. The practice of increasing engine size has roots in motorsports and performance enhancement, becoming increasingly accessible to motorcycle enthusiasts seeking greater power.
Subsequent sections will delve into the specific components included, the installation process, performance gains achievable, and considerations regarding compatibility and engine management. This will provide a complete overview of achieving enhanced engine performance.
1. Increased Displacement
The core principle behind a 107 big bore enhancement lies in altering the fundamental volume within the engine’s cylinders. Displacement, measured in cubic inches, dictates the total space the pistons sweep through. By increasing this space, the engine has the potential to draw in more air and fuel during each combustion cycle, the very lifeblood of power production. The 107 kit represents a deliberate increase from a smaller stock displacement, typically 96 or 103 cubic inches, aiming to transform the bike’s performance character. A veteran rider, accustomed to the limitations of his factory-standard bike, might experience a marked difference in throttle response and acceleration after such a conversion. The change is not mere perception, but a tangible result of the engine’s enhanced capacity.
This expansion in volume, however, is not a solitary act. It triggers a cascade of effects throughout the engine. The augmented intake requires a corresponding adjustment to fuel delivery; the engine control unit (ECU) must be recalibrated to provide the correct air-fuel mixture. Similarly, the increased pressure generated during combustion demands stronger components, like forged pistons, to withstand the added stress. Without these supporting modifications, the potential of the increased displacement may not be fully realized, or, worse, the engine’s long-term reliability could be compromised. The connection is crucial, since it is not only the piston dimension that matters. Choosing the right components, in the installation quality, and fine-tuning, are the other three legs of this approach. It is a system-wide adjustment with displacement increase at the center.
In essence, increased displacement within a 107 kit serves as the catalyst for a comprehensive engine upgrade. It provides the foundation for enhanced performance, but its success hinges on the careful integration of other supporting components and precise tuning. The challenge lies not only in achieving peak power, but in maintaining the engine’s integrity and longevity, creating a harmonious balance between increased output and enduring reliability. Understanding this relationship is key to appreciating the true potential and responsible application of a 107 big bore modification.
2. Cylinder Material
The story of a 107 big bore conversion is etched not just in increased volume, but in the very substance that contains the controlled explosions: the cylinder material. The original cylinders, often sufficient for stock displacement, are now tasked with containing significantly higher pressures and temperatures. The choice of material becomes paramount, a silent guardian against catastrophic failure. Cast iron, the traditional choice, offers cost-effectiveness and reasonable heat dissipation. However, its weight and limitations under extreme stress often push enthusiasts toward alternatives. Aluminum alloys, often with a specialized lining, emerge as contenders. They shed weight, improving the bike’s handling, and offer superior heat transfer, a crucial factor in preventing overheating and engine damage. Each material whispers a different tale of compromise and performance.
Consider a seasoned Harley mechanic, painstakingly assembling a 107 kit for a customer’s touring bike. He recalls a previous installation where a less-reputable kit, utilizing substandard cylinder material, resulted in premature wear and eventual cylinder wall failure. The increased heat and pressure, combined with the material’s inability to withstand the stress, led to a costly and frustrating experience for the owner. This time, he insists on cylinders crafted from a high-silicon aluminum alloy, known for its exceptional strength and thermal conductivity. The small premium in cost is an investment in the engine’s longevity, ensuring miles of reliable performance under demanding conditions. The choice wasn’t merely about price; it was about peace of mind.
Ultimately, the selection of cylinder material within a 107 big bore kit is a decision that resonates far beyond the spec sheet. It’s a commitment to reliability, performance, and the enduring spirit of the machine. While increased displacement grabs headlines, the composition of the cylinders is the unsung hero, quietly containing the power within and ensuring the engine’s song continues for years to come. The lesson is that the right material choice is not a mere detail, but a foundational element in achieving the desired outcome.
3. Piston Design
In the theater of a 107 big bore kit, the piston is not a mere player; it is the lead actor. Its design dictates the engine’s breathing, its capacity for power, and ultimately, its resilience against the relentless forces of combustion. The piston is the direct recipient of the ignited fuel-air mixture, translating that explosive energy into motion. Its form, its material composition, and its interaction with the cylinder walls define the character of the upgraded engine. Neglecting this critical element can turn a promising performance enhancement into a mechanical tragedy.
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Dome Profile
The dome, or lack thereof, on a piston dictates compression. A domed piston compresses the air/fuel mixture into a smaller space, yielding higher combustion pressures and increased power. A flat-top piston reduces compression, typically used in conjunction with other modifications to fine-tune engine characteristics. Recall the tale of the custom builder, chasing maximum horsepower, who opted for aggressively domed pistons. The engine roared, but detonation soon followed, hammering the bearings and shortening the engine’s lifespan. The lesson: dome profile must harmonize with other engine parameters.
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Piston Material
Cast pistons, once commonplace, are now often relegated to less demanding applications. Forged pistons, born from intense heat and pressure, offer superior strength and resistance to deformation. Consider the endurance racer, pushing his machine to the limits lap after lap. Cast pistons would crumble under the strain, while forged pistons endure, delivering consistent power even when the engine is pushed into the red zone. Material selection is a pact with reliability.
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Skirt Design
The piston skirt guides the piston’s movement within the cylinder, preventing wobble and ensuring smooth operation. A short skirt reduces weight and friction, but sacrifices stability. A longer skirt provides better support, but adds weight and can increase friction. A well-designed skirt balances these competing factors, minimizing wear on both the piston and the cylinder walls. Imagine a piston with an ill-fitting skirt, slapping against the cylinder walls with each stroke, a harbinger of impending failure.
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Ring Grooves and Lands
The grooves that house the piston rings and the lands between them are critical for maintaining compression, sealing combustion gases, and managing oil. Poorly machined grooves can lead to ring flutter, loss of compression, and oil consumption. An experienced engine builder meticulously checks ring end gap and groove clearances, ensuring proper sealing and preventing blow-by. The rings, properly seated in their grooves, form a critical seal, ensuring all the energy of the combustion goes towards pushing the piston down and propelling the motorcycle forward.
Ultimately, the piston, often overlooked in the enthusiasm for increased displacement, is a key determinant of the 107 big bore kit’s success. Its design, material, and precise fit define the engine’s performance, reliability, and longevity. The tale of the 107 is, in many ways, the tale of its piston. A carefully considered piston design transforms a simple engine upgrade into a lasting enhancement of the riding experience.
4. Compression Ratio
The compression ratio, a seemingly simple numerical expression, wields significant influence over the effectiveness of a 107 big bore kit. It represents the proportion between the cylinder’s volume when the piston is at its lowest point and its volume when the piston is at its highest. This ratio, meticulously engineered or carelessly overlooked, can either unlock the kit’s full potential or condemn the engine to premature failure. A higher compression ratio squeezes the air-fuel mixture more tightly, leading to a more potent explosion and, consequently, greater power output. However, this comes at a cost: increased stress on engine components and a heightened susceptibility to detonation, a destructive form of uncontrolled combustion.
Consider the case of a custom bike shop renowned for its 107 conversions. They meticulously calculate the compression ratio for each build, taking into account factors such as piston dome volume, cylinder head chamber size, and deck height. One particular project, a high-performance bagger, demanded maximum power. They opted for a compression ratio bordering on the aggressive, requiring high-octane fuel and precise tuning to avoid detonation. The result was a beast of a machine, delivering exhilarating acceleration. However, another builder, chasing similar gains with a less discerning approach, increased the compression ratio without considering the consequences. The engine suffered from chronic detonation, leading to cracked pistons and bent connecting rods. The lesson learned: a high compression ratio is a double-edged sword, demanding respect and meticulous attention to detail. Improper tuning could lead to catastrophic failure.
Ultimately, the compression ratio is a crucial parameter in any 107 big bore kit installation. It is a carefully balanced equation, where increased power must be tempered with considerations for engine durability and fuel requirements. Understanding this relationship is paramount for anyone seeking to unlock the full potential of a 107 conversion, ensuring a harmonious blend of performance and reliability. The choice of the compression ratio, in the end, is a determining factor of a kit’s success.
5. Fuel Management
Fuel management, in the realm of engine modification, is akin to the nervous system in a living organism. It is not merely an accessory but a vital necessity, especially when considering the installation of a “harley 107 big bore kit.” The modification fundamentally alters the engine’s appetite, demanding a precise calibration to avoid starvation or overindulgence, both detrimental to performance and longevity. The engine’s heart relies on the accuracy of air and fuel.
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Air-Fuel Ratio Tuning
The correct air-fuel ratio is the foundation of efficient combustion. A 107 kit increases the engine’s displacement, meaning it requires more fuel to maintain the ideal ratio. Failure to adjust this ratio results in a lean condition, potentially leading to overheating, detonation, and engine damage. The legend is from the custom chopper builder who neglected his bike. The bike runs the 107 big bore kit. He ignored the fuel management step. The pistons were heat damaged, resulting in premature and total failure.
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ECU Recalibration
The Engine Control Unit (ECU) is the brain of the fuel management system, responsible for interpreting sensor data and adjusting fuel delivery accordingly. The 107 kit necessitates an ECU recalibration to accommodate the engine’s new operating parameters. A poorly calibrated ECU can lead to poor performance, reduced fuel economy, and even engine damage. Without ECU the bike will not perform.
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Fuel Injector Capacity
Stock fuel injectors may lack the capacity to deliver the increased fuel volume required by the 107 kit. Upgrading to higher-flow injectors ensures adequate fuel delivery across the entire RPM range. A custom builder, pushing his engine to its limits, neglected to upgrade the injectors, resulting in fuel starvation at high RPM and a significant power loss. Fuel starvation will cause the engine to fail.
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Throttle Body Sizing
The throttle body regulates the amount of air entering the engine. While not always necessary, upgrading to a larger throttle body can improve airflow and enhance throttle response, particularly in conjunction with other performance modifications. Proper throttle will ensure smooth power delivery.
In conclusion, fuel management is not an optional extra but an integral component of a successful “harley 107 big bore kit” installation. It is the intricate dance between air and fuel, orchestrated by the ECU and delivered by the injectors, that determines the engine’s performance, reliability, and longevity. Neglecting this critical aspect is akin to building a house on a shaky foundation, inevitably leading to a collapse.
6. Installation Precision
The true potential of a “harley 107 big bore kit” is not merely unlocked by its components, but rather through the meticulous execution of its installation. Each step, each torque specification, each carefully measured clearance contributes to the symphony of mechanical harmony or descends into a cacophony of premature wear and catastrophic failure. The story of any big bore kit begins not on the dyno, but in the methodical hands of the technician.
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Cylinder Head Alignment
The cylinder heads, the gatekeepers of combustion, must be aligned with utmost precision. Misalignment leads to uneven compression, compromised combustion efficiency, and accelerated wear on valve train components. The tale persists of a seasoned mechanic, rushed on a deadline, who neglected to properly align the cylinder heads. The engine, though powerful, suffered from chronic valve problems, a constant reminder of the neglected detail. Improper cylinder head will cause to complete engine failure.
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Piston Ring End Gap
The small gap in the piston rings, seemingly insignificant, plays a crucial role in sealing the combustion chamber. Insufficient end gap results in ring butting, leading to scoring of the cylinder walls and a rapid loss of compression. Excessive end gap compromises the seal, allowing combustion gases to escape and reducing power output. The consequences of poor ring end gap. Proper Piston ring will ensure to proper combustion and power delivery.
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Torque Specifications
Each bolt, each fastener, tightened to its precise torque specification, contributes to the structural integrity of the engine. Undertightening leads to loosening and potential component failure. Overtightening stresses the metal beyond its limits, leading to cracking and eventual breakage. Imagine the scenario of a weekend warrior, overzealous with his wrench, snapping a cylinder head bolt. The repair, costly and time-consuming, served as a harsh lesson in the importance of precision.
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Camshaft Timing
The camshaft, the brain of the valve train, dictates the precise timing of valve opening and closing. Incorrect camshaft timing leads to reduced power, poor fuel economy, and increased emissions. Camshaft timing is the key to making power.
In conclusion, installation precision is not merely a checklist item but a fundamental requirement for realizing the potential of a “harley 107 big bore kit.” It is the meticulous attention to detail, the unwavering adherence to specifications, that transforms a collection of components into a harmonious and powerful engine. The story of any successful big bore conversion is, ultimately, a testament to the skill and dedication of the installer.
7. Reliability Assurance
The promise of a “harley 107 big bore kit” is undeniably alluring: increased power, enhanced throttle response, and a transformation of the motorcycle’s character. However, this promise rings hollow without a steadfast commitment to reliability assurance. The increased stress, higher temperatures, and altered dynamics inherent in a displacement upgrade demand a proactive approach to safeguarding the engine’s longevity. It is a crucial consideration, with cause and effect relationship with the whole upgrading process.
Consider the tale of two riders, both enticed by the allure of the 107 kit. The first, fueled by impatience and a desire for immediate gratification, opted for the cheapest kit available and entrusted its installation to a less-than-reputable mechanic. The result was predictable: premature engine failure, a cascade of broken components, and a deep sense of regret. The second rider, however, approached the upgrade with meticulous care. He invested in a high-quality kit from a reputable manufacturer, researched qualified installers, and insisted on comprehensive testing and tuning. The result was a machine that not only delivered exhilarating performance but also stood the test of time, a testament to the power of diligent reliability assurance. It starts with proper planning and component selection, then meticulous execution of the installation process.
Reliability assurance, in the context of a 107 big bore kit, is not a passive hope but an active pursuit. It demands careful component selection, meticulous installation, and ongoing maintenance. It requires a deep understanding of the engine’s dynamics and a willingness to invest in quality over cost. A bike properly upgraded is not only powerful, but will last long to enjoy the ride. While the pursuit of increased performance is a worthy endeavor, it must be tempered with a unwavering commitment to reliability assurance, ensuring that the enhanced power does not come at the expense of the engine’s longevity. The pursuit is a responsible approach to a satisfying and sustainable performance upgrade.
Frequently Asked Questions
The allure of increased displacement often leads to numerous inquiries. Presented below are answers to some commonly raised questions, providing clarity and context to prospective upgraders.
Question 1: Will a 107 kit void the factory warranty?
Modifying an engine invariably impacts the factory warranty. The degree of impact often depends on the manufacturer’s policies and the nature of the modification. A widely held understanding suggests that modifications not directly related to the failure may not void the entire warranty, but components directly affected by the 107 kit would likely fall outside the scope of coverage. Consultation with a dealership is recommended before undertaking such modifications. Understand that warranty may be forfeited with significant modification.
Question 2: Is professional installation required, or can it be a DIY project?
While some mechanically inclined individuals undertake 107 kit installations themselves, the complexity of the procedure necessitates a high degree of skill and precision. Improper installation leads to engine damage and reduced lifespan. A professional installer possesses the necessary tools, expertise, and experience to ensure proper fitment and calibration. The cost of professional installation often outweighs the potential expense of rectifying self-inflicted errors. Professional installation is highly recommended.
Question 3: What kind of performance gains can be expected?
Performance gains vary depending on the specific kit, supporting modifications, and tuning. However, a properly installed and tuned 107 kit typically yields a significant increase in horsepower and torque, particularly in the low to mid-range. Dyno charts showcase tangible improvements in power output across the RPM range. The perceived difference in acceleration and overall riding experience is substantial. Expect to see marked improvement.
Question 4: What supporting modifications are typically required?
A 107 kit often necessitates supporting modifications to maximize its potential and ensure reliability. These include, but are not limited to, upgraded fuel injectors, a performance air cleaner, and a recalibrated ECU. Exhaust modifications are often recommended to improve exhaust flow and further enhance performance. Neglecting these supporting modifications often leads to diminished returns and potential engine strain. Supporting modifications are vital to the success.
Question 5: Does a 107 kit impact fuel economy?
Increasing engine displacement generally impacts fuel economy. A 107 kit often results in a slight decrease in fuel efficiency, particularly during aggressive riding. However, with proper tuning and responsible throttle control, the reduction in fuel economy can be minimized. The trade-off between increased performance and decreased fuel efficiency is a consideration for prospective upgraders. Fuel efficiency may suffer a slight decline.
Question 6: What is the typical lifespan of an engine with a 107 kit?
The lifespan of an engine with a 107 kit is influenced by numerous factors, including the quality of the kit, the precision of the installation, and the consistency of maintenance. A well-maintained engine with a properly installed kit should provide years of reliable service. However, neglecting maintenance or subjecting the engine to excessive abuse will undoubtedly shorten its lifespan. A well-maintained and installed kit should last.
Ultimately, a 107 big bore kit offers a compelling avenue for enhancing motorcycle performance. However, it is essential to approach the upgrade with informed awareness, diligent planning, and a steadfast commitment to quality and precision.
The subsequent section explores cost considerations associated with such a modification.
Expert Guidance for Your Harley 107 Big Bore Kit
Embarking on a performance upgrade requires careful consideration. The path to a successful “harley 107 big bore kit” installation is paved with informed decisions and meticulous execution. Heed these guidelines, gleaned from countless engine rebuilds and dyno sessions, to ensure optimal performance and longevity.
Tip 1: Prioritize Quality Components.
The market abounds with kits of varying quality. Opt for a reputable manufacturer with a proven track record. Inferior components compromise performance and risk premature engine failure. Remember the cautionary tale of the bargain kit that cost far more in the long run due to repeated repairs and eventual engine replacement. Quality parts can save you headaches in the long run.
Tip 2: Seek Expertise in Installation.
While the allure of a DIY project is strong, engine modification demands precision. Entrust the installation to a qualified mechanic experienced with “harley 107 big bore kit” applications. Improper installation leads to diminished performance and potential engine damage. Remember the mechanic who always double-checked the details. Details matter.
Tip 3: Invest in Proper Tuning.
A 107 kit necessitates precise fuel and ignition tuning. A poorly tuned engine suffers from reduced power, poor fuel economy, and increased risk of detonation. Invest in a professional dyno tune to optimize performance and ensure engine reliability. Fuel is key.
Tip 4: Address Supporting Systems.
The engine upgrade ripples through the entire system. Ensure that fuel delivery, exhaust flow, and cooling capacity are adequate for the increased power output. Overlooking these supporting systems compromises performance and shortens engine life. Ensure all related parts are ready for the upgrade.
Tip 5: Monitor Engine Health.
Post-installation, closely monitor engine temperature, oil pressure, and overall performance. Address any anomalies promptly to prevent minor issues from escalating into major problems. Regular maintenance and vigilant observation are crucial for long-term reliability. Pay attention to the data.
Tip 6: Be Aware of Riding Style.
The exhilaration of increased power can tempt aggressive riding. However, excessive strain shortens engine life. Moderate throttle inputs and mindful gear selection contribute to long-term reliability. Ride mindfully and your bike will enjoy it.
These guidelines serve as a roadmap for a successful “harley 107 big bore kit” installation. Adhering to these principles ensures optimal performance, enhanced reliability, and a rewarding riding experience.
The article’s conclusion now awaits.
Harley 107 Big Bore Kit
The journey into enhancing a Harley-Davidson engine through a “harley 107 big bore kit” has revealed a landscape where increased displacement intertwines with meticulous engineering and thoughtful execution. From the foundational choice of cylinder material to the nuanced adjustments in fuel management, each element contributes to a transformed riding experience. Installation precision, a cornerstone of reliability, emerges not as a mere technicality, but as a testament to the craft. Ultimately, the pursuit of enhanced power requires a harmonious balance of ambition and responsibility.
The tale of the 107 conversion is more than a chronicle of increased cubic inches; it is a narrative of dedication to the enduring spirit of the machine. For within each meticulously installed piston, within each precisely tuned engine, lies the opportunity to extend a legacy of power and precision. Let the pursuit of performance be guided by knowledge, tempered by caution, and driven by a deep respect for the iron horse beneath. The road awaits.
