The Namura NA-50098-BK Top End Kit is a complete replacement solution for select Polaris ATV and side-by-side engines. Designed with a 92.97 mm piston and 11:1 compression ratio, this kit includes the piston, piston rings, wrist pin, retaining clips, top-end bearing, and gasket kit needed for a dependable top-end rebuild. It is engineered for fitment on 2017–2019 Polaris Sportsman 450 HO models, select Sportsman 450 HO EPS models, and Polaris ACE 500 models.
The piston uses Namura’s MOS2, or Teflon/Molybdenum, coated skirts. This rolled-on coating process creates a durable bond while helping reduce friction, improve heat transfer, and minimize the risk of cold seizures. Machined smooth heads help reflect combustion heat and reduce carbon buildup, supporting piston protection and consistent engine performance. The anodized dome improves heat resistance and durability compared with standard non-anodized piston designs.
Manufactured using a hypereutectic casting process, the Namura piston contains a higher silicon content to help control expansion, increase wear resistance, and withstand elevated cylinder temperatures. The included components are matched for a practical top-end service, helping simplify installation and restore engine operation. Verify engine year, model, bore specification, and existing cylinder condition before ordering to ensure proper fitment. This kit is identified by Namura manufacturer part number NA-50098-BK and vendor part number 186-5098B.
Features:
- Complete top-end kit includes piston, rings, wrist pin, retaining clips, top-end bearing, and gasket kit
- 92.97 mm piston size with an 11:1 compression ratio
- MOS2 Teflon/Molybdenum coated skirts help reduce friction, improve heat transfer, and minimize cold-seizure risk
- Machined smooth piston head helps reflect combustion heat and reduce carbon buildup
- Anodized piston dome improves heat resistance and durability
- Hypereutectic casting process provides controlled expansion, wear resistance, and improved high-temperature capability
- Fits select 2017–2019 Polaris Sportsman 450 HO, Sportsman 450 HO EPS, and ACE 500 models
- Brand: Namura; manufacturer part number: NA-50098-BK; vendor part number: 186-5098B
Fitment:
2017 Polaris ACE 500
2017 Polaris Sportsman 450 HO
2017 Polaris Sportsman 450 HO EPS
2018 Polaris ACE 500
2018 Polaris Sportsman 450 HO
2018 Polaris Sportsman 450 HO EPS
2019 Polaris ACE 500
2019 Polaris Sportsman 450 HO
2019 Polaris Sportsman 450 HO EPS