J.E. Pistons 391731 Powersports Ultra Series Piston Kit - Standard Bore 4.25in. - 11.25:1 Compression

Bore: 4.250in.
Compression: 11.25:1 Compression
Sizing: Standard Bore

Piston Head Shape: Dished.
Stroke Length: 4.5In.

In-house forging has allowed JE to develop proprietary Aligned Grain Flow Technology forging technology that directs the grain flow of the aluminum to flow around critical areas of the piston, increasing strength. Lateral gas ports channel combustion gases to the back of the top ring groove, which adds pressure behind the compression ring to keep it pushed against the cylinder, providing improved and more consistent ring seal, critical in boosted applications. Ultra-thick ring lands aid in maintaining ring stability in forced induction and high-horsepower N/A engines, contributing to consistent ring seal and consistent power. Thermal Barrier Crown Coating - a ceramic coating on the piston crown - greatly reduces heat transfer into the piston material, decreasing fatigue and improving longevity. Tuff Skirt - a proprietary, moly-based dry film skirt coating is applied in-house and reduces operating friction for better wear resistance. Accumulator groove provides additional volume to trap unwanted gases below the top ring to keep pressure low and ring seal and performance high. Double pin oilers - two oil channels feed into the pin bore to maintain proper lubrication to improve wrist pin and pin bore wear resistance. Includes upgraded 9310 wrist pins: stronger, thicker wrist pin material is designed to withstand additional loads of forced induction applications. Sold as a complete kit with all necessary pistons, rings, wrist pins and wire locks under one part number.

Vehicle Fitment:

2018-2020 Harley Davidson FLDE Deluxe 107
2018-2019 Harley Davidson FLFB Fat Boy 107
2018-2024 Harley Davidson FLFBS Fat Boy 114
2021 Harley Davidson FLH Electra Glide Revival
2018-2021 Harley Davidson FLHC Heritage Classic 107
2018-2024 Harley Davidson FLHCS Heritage Classic 114
2023 Harley Davidson FLHFB Electra Glide Highway King
2017-2024 Harley Davidson FLHRXS Road King Special
2017-2024 Harley Davidson FLHTK Ultra Limited
2017-2019 Harley Davidson FLHTKL Ultra Limited Low
2017-2023 Harley Davidson FLHXS Street Glide Special
2022-2023 Harley Davidson FLHXST Street Glide ST
2024 Harley Davidson FLI Hydra-Glide Revival
2018-2021 Harley Davidson FLSB Sport Glide 107
2018-2021 Harley Davidson FLSL Softail Slim 107
2020-2024 Harley Davidson FLTRK Road Glide Limited
2017-2019 Harley Davidson FLTRU Road Glide Ultra
2017-2024 Harley Davidson FLTRX Road Glide
2017-2023 Harley Davidson FLTRXS Road Glide Special
2022-2023 Harley Davidson FLTRXST Road Glide ST
2018-2020 Harley Davidson FXBB Street Bob 107
2018-2019 Harley Davidson FXBR Breakout 107
2023-2024 Harley Davidson FXBR Breakout 117
2018-2020 Harley Davidson FXBRS Breakout 114
2019-2020 Harley Davidson FXDRS FXDR 114
2018-2019 Harley Davidson FXFB Fat Bob 107
2018-2023 Harley Davidson FXFBS Fat Bob 114
2018-2020 Harley Davidson FXLR Low Rider 107
2020-2021 Harley Davidson FXLRS Low Rider S 114
2022-2024 Harley Davidson FXLRS Low Rider S 117
2022-2024 Harley Davidson FXLRST Low Rider ST 117
2022 Harley Davidson FXRST Low Rider El Diablo 117
2020-2024 Harley Davidson FXST Softail Standard 107