S&S Cycle 129" Power Package Big Bore Kit for M8 107"
S&S Cycle 129" Power Package Big Bore Kit for M8 107"
About this product
About this product
Unleash the full potential of your Harley-Davidson® Milwaukee-Eight® 107" engine with the S&S Cycle 129" Power Package Big Bore Kit. This comprehensive, bolt-on upgrade transforms your M8 into a formidable 129" powerhouse, delivering significant gains in horsepower and torque without requiring any case machining.
Description
Designed for motorcycle enthusiasts seeking a substantial performance boost, the S&S Cycle 129" Power Package is a complete bolt-on solution to elevate your 107" Milwaukee-Eight® engine. This kit features high-quality 4.32" bore cylinders paired with robust 11.0:1 compression ratio forged pistons, meticulously engineered to achieve a 129" displacement. The heart of this upgrade includes an S&S oil pump and cam plate, finished with a distinctive blue anodized coating, ensuring superior lubrication and engine longevity. It boasts independent scavenge sections for both the flywheel cavity and cam chest, alongside debris screens and a magnet in the cam chest to prevent harmful particles from entering the oil system. Oil flow capacity is significantly increased on both the feed and scavenge sides, while an adjustable pressure relief valve allows for fine-tuning even after installation. The kit is further enhanced with S&S Quickee pushrods, premium tappets, and hard-anodized, black-coated billet aluminum tappet cuffs. Performance is amplified by S&S 550 cams, specifically designed for big bore applications, and high-performance conical single-wire valve springs capable of handling cams up to 0.605" lift. Proudly Made in the USA, this S&S Cycle big bore kit is compatible with VVT models, offering a premium upgrade for your M8.
Features & Highlights
- Effortless Power Upgrade: Transform your 107" Milwaukee-Eight® engine into a massive 129" displacement with 4.32" bore cylinders and 11.0:1 compression ratio forged pistons, all through a straightforward bolt-on installation that requires no case machining.
- Optimized Engine Longevity: Features an S&S oil pump and cam plate with a blue anodized finish, incorporating independent scavenge sections, debris screens, and a cam chest magnet to ensure superior oil cleanliness and component protection.
- Enhanced Oil System Performance: Benefit from increased oil flow capacity on both the feed and scavenge sides, plus an adjustable pressure relief valve that can be fine-tuned while installed in the engine for optimal lubrication.
- High-Performance Valvetrain: Includes S&S Quickee pushrods, premium tappets, and hard-anodized, black-coated billet aluminum tappet cuffs for reliable, high-lift operation.
- Big Bore Specific Cams: Equipped with S&S 550 cams, precisely designed to maximize the performance of big bore applications, complemented by high-performance conical single-wire valve springs supporting up to 0.605" lift.
- American-Made Quality: Experience superior craftsmanship and reliability with components proudly Made in the USA.
Technical Specifications
- Brand: S&S Cycle
- Product Name: Power Package
- Model: Performance Kit (550C)
- Displacement: 129"
- Bore Size: 4.32"
- Stroke Length: 4.375"
- Compression Ratio: 11.0:1
- Cam Drive Type: Chain
- Cam Lift Support: Up to 0.605"
- Cooling System: Oil Cooled
- Color/Finish: Non-Highlighted Fins, Wrinkle Black
- Features: Black Pushrod Tubes, Cam Chain Tensioner
- Units: Kit
- Vendor Part Number: 310-1226D
Important to Know
- Not for any Trike models.
- Intake/rocker cover gaskets not included.
Shipping & Return
Shipping & Return
Free shipping to GLS parcel shop parcel box for purchases over DKK 1,000.
GLS home delivery costs DKK 59.
We do our best to ship your order as quickly as possible. All orders are generally packed within 24 hours on weekdays.
There is a 14-day return policy. Read more
Specifications
310-1226D
Non-Highlighted Fins, Wrinkle Black
Performance Kit
Power Package
550C
4,320"
11,0:1
129"
4,375"
298.45 mm
490.728 mm
682.625 mm
Chain
Black Pushrod Tubes, Cam Chain Tensioner
Kit
Oil Cooled
Reviews


Who is behind Parts Denmark
Martin and William are the duo behind Parts Denmark — an unlikely but awesome combo of a tech-savvy young IT wizard and a seasoned motorcycle guru who’s seen (and fixed) it all. Together, we’ve built a team with big ambitions, plenty of passion, and a shared mission to create great things — side-by-side with you.
Based in Denmark
Fast customer support
Over 100.000 Products
2-Year Full Warranty
Your peace of mind is our priority. Every product in our shop comes with a comprehensive 2-year warranty, so you can hit the road with full confidence.
Support in Danish, Swedish, German & English
Whether you are upgrading your exhaust or choosing a new helmet, our team of seasoned riders is ready to provide professional guidance for your specific bike.
Free Shipping Over 200€ (EU)
Shop your favorite gear without worrying about extra costs. We offer free shipping on all orders over 200€ (EU), ensuring your parts reach you safely and affordably.
Authorized Parts Europe Dealer
As a certified Parts Europe supplier, we guarantee 100% authentic, high-quality motorcycle parts and accessories directly from the world's leading manufacturers.

