J.E. PISTONS 391731 Je Ultra Piston Kit Standard 4.25 11.25

( Brand: J.e. Pistons ), ( Manufacturer Part Number: 391731 ), ( Part Type: Piston ), ( Make: Harley )

Review J.E. PISTONS Je Powersports Ultra Series Piston Kit Standard Bore 4.25 Inch 11.25

The JE Pistons 391731 Ultra piston kit is a high-performance solution for standard 4.25-inch bore, 11.25-inch stroke applications. This kit is part of JE Pistons' Ultra series, which is renowned for its advanced engineering and design that delivers exceptional power and reliability.

Each piston in this kit is meticulously crafted from forged 2618-T6 aluminum, ensuring superior strength and durability. The piston crowns are designed with a domed shape, providing optimal combustion efficiency and allowing for larger valve sizes. The piston skirts are treated with JE's proprietary DiamondLike Carbon (DLC) coating, which minimizes friction and enhances ring seal.

The piston pins are made from 300M steel, providing the necessary strength to withstand the demands of high-performance applications. The pistons are also equipped with JE's patented Pro-Fit wrist pins, which offer increased pin retention and durability.

Additionally, this kit includes JE's top ring groove technology, which ensures proper ring alignment and sealing. The pistons are also designed to work with a variety of connecting rods, making it a versatile option for different engine builds.

The JE Pistons 391731 Ultra piston kit is a perfect choice for enthusiasts and professionals seeking optimal power and reliability from their engines. With its advanced design, high-quality materials, and meticulous manufacturing process, this piston kit is sure to deliver impressive results and provide a lasting solution for your engine build.

Pros and Cons of Buying JE Pistons 391731 Ultra Piston Kit for a 4.25 in. Bore and 11.25 in. Stroke Engine

The JE Pistons 391731 Ultra piston kit is a popular choice among engine builders and high-performance enthusiasts for its durability, strength, and precision. This piston kit is designed for a 4.25-inch bore and 11.25-inch stroke engine. In this analysis, we'll discuss the advantages and disadvantages of purchasing this piston kit, ending with a conclusion and recommendation.

1. High-Strength Design: JE Pistons are known for their high-strength designs, which are essential for high-performance applications. The Ultra piston kit is no exception, boasting a forged 2618-T6 aluminum alloy construction.

2. Precision Manufacturing: The pistons are manufactured using JE's advanced CNC machining process, ensuring a perfect fit and optimal engine performance.

3. Low-Friction Design: The piston kit features a low-friction design, which minimizes wear and tear on the piston rings and skirt, enhancing engine longevity.

4. Customizable: The Ultra piston kit is available in various sizes and configurations, allowing users to tailor the pistons to their specific engine requirements.

5. Heat Resistance: The pistons are designed to handle high temperatures, making them suitable for performance engines that operate under extreme conditions.

1. Cost: The JE Pistons 391731 Ultra piston kit is more expensive compared to other aftermarket piston options, which may be a deterrent for some buyers.

2. Complex Installation: Installing the pistons requires specialized tools and expertise, which may add to the overall cost and complexity of the project.

3. Limited Warranty: The piston kit comes with a limited warranty, which may not provide adequate coverage for some users, especially those planning to use the engine for high-performance applications.

The JE Pistons 391731 Ultra piston kit offers several advantages, including high-strength design, precision manufacturing, low-friction design, customizability, and heat resistance. However, its higher cost, complex installation process, and limited warranty may be drawbacks for some buyers.

If you are building a high-performance engine and are looking for pistons that can handle the increased stresses and temperatures, the JE Pistons 391731 Ultra piston kit is an excellent choice. Despite its higher cost and complex installation process, the pistons' durability, strength, and precision make them worth the investment for performance enthusiasts. However, if budget is a concern, there are alternative aftermarket piston options available that may offer similar performance at a lower cost.

Details:

Double pin boilers - two oil channels feed into the bore to maintain proper lubrication improve wrist and wear resistance. Thermal Barrier Crown Coating - a ceramic coating on the piston crown greatly reduces heat transfer into material, decreasing fatigue and improving longevity. Ultra-thick ring lands aid in maintaining stability forced induction and high-horsepower N/A engines, contributing to consistent seal power. In-house forging has allowed JE to develop proprietary Aligned Grain Flow Technology that directs the grain flow of aluminum around critical areas piston, increasing strength.

Sold as a complete kit with all necessary Pistons, rings, wrist pins and wire locks under one part number. Compression: 11.25:1 Compression, Sold as: Kit. Any damage claims may be exchanged for the identical item only. Stroke length : 4.5In.

Sizing: Standard Bore, Bore: 4.250in. Tiff Skirt - a proprietary, Molly-based dry film skirt coating is applied in-house and reduces operating friction for better wear resistance. Piston Head Shape: Dished. Lateral gas ports channel combustion gases to the back of top ring groove, which adds pressure behind compression keep it pushed against cylinder, providing improved and more consistent seal, critical in boosted applications.

part #: 391731 price

• $682.99

specifications pistondon:

• brand: J.e. Pistons
• mpn: 391731
• part type: Piston
• make: Harley

general pistondon:

• Motorcycle Scooter Parts Accessories > Engines Engine Parts > Pistons, Rings Piston Kits
• condition: New

offer pistondon:

• availability: In Stock
• quantity: 7
• started: November 4, 2025
• options: Ship-to-home
• sold: 0

payments pistondon:

• other
• credit card: Discover
• wallet: Google-pay

returns pistondon:

• time: 30 Days
• paid by: Seller
• policy: Returns Accepted

shipping pistondon:

• service: Economy, Standard, Expedited
• cost: $0.00
• type: Fixed
• transit: 2-6 Days
• class: Economy, Standard, Expedited

seller pistondon:

• city: Loudon, Tennessee
• rating: 99.3%
• # reviews: 595969

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