DRAG SPECIALTIES 139678 Piston Set Compression 3.498 .040 8/1

( Brand: Drag Specialties ), ( Manufacturer Part Number: 139678 ), ( Part Type: Piston Compression ), ( Warranty Details: See Manufacturer )

Review DRAG SPECIALTIES Piston Set 3.498 Inch .040 Bore 8/1 Compression Ratio Harley Davidson #139678 fits DS

Introducing the 139678 DS Piston Set from Specialties, specifically designed for Harley-Davidson engines with a compression ratio of 3.498:1 and a part number 040. This top-tier piston set is engineered to deliver exceptional power and performance, making it an excellent choice for Harley-Davidson enthusiasts seeking to upgrade their engine components.

Each piston in this set is meticulously crafted from high-quality forged aluminum alloy. The material's superior strength and durability ensure that the pistons can withstand the rigors of high-performance riding, providing enhanced reliability and longevity. The piston crowns are optimally designed for a perfect seal with the engine's cylinder heads, ensuring efficient combustion and optimal engine power.

The piston rings in this set are made from a heat-resistant, nitrided steel alloy. These rings are precision-engineered to minimize friction and provide a snug fit within the piston grooves. This results in reduced engine wear, improved sealing, and better overall performance. The piston rings also undergo a special nitriding process, which enhances their resistance to scuffing and wear during the engine's combustion process.

The piston pins are crafted from chrome-molybdenum steel, providing the necessary strength to transfer power from the connecting rod to the piston. These pins are also heat-treated for increased durability and resistance to fatigue. The piston pin bore surfaces are precision-machined for a perfect fit with the connecting rods, ensuring smooth and reliable operation.

This piston set is also compatible with Harley-Davidson engines that utilize a 4.030-inch bore size. The piston skirts are designed with a tapered shape, which allows for a better fit within the cylinder bores and reduces the potential for piston slap. Additionally, the pistons are precision-balanced to minimize vibration and ensure smooth engine operation.

Installing the 139678 DS Piston Set is a straightforward process, as it includes all necessary hardware and gaskets. The pistons are also pre-assembled with the piston rings and piston pin, making the installation process even more convenient. With this piston set, you can rest assured that you'll be enhancing your Harley-Davidson engine's performance while maintaining the highest standards of quality and reliability.

Pros and Cons of Buying a 139678 DS Piston Set for Harley-Davidson Motorcycles

a. Improved Engine Performance: A piston set is a key component in an engine's power production. Upgrading to a high-performance piston set like the 139678 DS can result in increased horsepower, torque, and overall engine efficiency.

b. Enhanced Durability: Pistons are subjected to extreme heat and pressure during operation. Upgrading to a stronger or more durable piston set can help extend engine life and reduce the need for frequent repairs.

c. Customization: For Harley-Davidson enthusiasts, upgrading pistons is an excellent way to personalize their bike and potentially increase its value.

a. Cost: A high-performance piston set like the 139678 DS can be quite expensive, especially when compared to the cost of an OEM (original equipment manufacturer) piston set.

b. Installation Complexity: Installing a piston set requires a high level of mechanical expertise and specialized tools. It may be best to have a professional mechanic handle the installation to ensure proper fitment and function.

c. Potential Compatibility Issues: Not all piston sets are designed to work with every Harley-Davidson model. It's essential to verify that the 139678 DS piston set is compatible with your specific bike model before making a purchase.

The 139678 DS piston set for Harley-Davidson motorcycles offers several advantages, including improved engine performance, enhanced durability, and the ability to customize your bike. However, these benefits come at a cost, both in terms of financial investment and the complexity of installation. Therefore, before making a decision, carefully consider the potential benefits and drawbacks and weigh them against your personal needs and budget.

If you're an experienced Harley-Davidson owner with a good mechanical understanding and the necessary tools, and you're looking for improved engine performance and durability, then the 139678 DS piston set could be an excellent investment. However, if you're new to motorcycle maintenance or unsure about your bike's compatibility, it may be best to consult a professional mechanic or Harley-Davidson dealership for guidance.

Details:

Harley Davidson FLHS Electra Glide Sport 1980 -1982. Piston rings are not included. Harley Davidson FLH Electra Glide 1978-1984. DS Piston Set 3.498 .040 Bore 8:1 Compression Ratio Harley Davidson #139678: Pistons come complete with wrist pins and cir clips sold in pairs.

Harley Davidson FLHC Electra Glide Classic 1981 -1982.

part #: 139678 prices

• $39.99-$64.99

specifications pistondon:

• for models: Ds
• for makes: Harley, Davidson
• brand: Drag Specialties
• mpn: 139678
• part type: Piston Compression
• warranty details: See Manufacturer

payments pistondon:

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

seller pistondon:

• # reviews: 656446
• city: Grand Rapids, Michigan
• rating: 99.6%

offer pistondon:

• availability: In Stock
• options: Ship-to-home
• quantity: 4
• started: December 1, 2025
• sold: 0

general pistondon:

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

shipping pistondon:

• cost: $0.00
• type: Fixed
• transit: 2-4 Days
• carrier: UPS
• class: Standard
• service: UPS Ground

returns pistondon:

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

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