Keith Black 390 Hypereutectic Flat Top Piston Kit.030 For Harley FXR 80 Inch

Keith Black 390 Hypereutectic Flat Top Piston Kit.030 oversize for Harley FXR 80 Inch delivers higher power output, improved fuel efficiency, and extended engine longevity on 1984–1993 Big Twin Evolution engines. The lightweight piston is cast in a permanent steel mold and uses a hypereutectic alloy for durability and heat resistance, optimized for demanding riding conditions.

• Material: Keith Black hypereutectic alloy
• Oversize / Bore:.030 oversize to fit a 3.498-inch bore
• Compression: 8.5:1
• Heat management: Low heat transfer alloy keeps piston skirts cool, reducing expansion and wear
• Ring placement: High compression ring position enhances power output and detonation resistance
• Application: Fits Harley Davidson FXR models from 1984 to 1993
• Installation: Includes instructions for proper break-in and installation
• Part number: KB258.030

Keith Black flat top piston set is.030 oversize with an 8.6:1 compression ratio for 1984-up Big Twin Evolution models.

The Keith Black 390 hypereutectic alloy piston kit is engineered for high performance and durability in Harley Davidson FXR models from 1984 to 1993. Cast in a permanent steel mold, this lightweight piston promotes increased power output, improved fuel efficiency, and extended engine longevity. Designed with a.030 oversize to fit a 3.498-inch bore, the piston features an 8.5:1 compression ratio, optimizing engine performance while maintaining reliability. The premium hypereutectic alloy's low heat transfer properties keep the piston skirts cool, minimizing expansion and reducing wear under demanding conditions. This advanced material, combined with high compression ring placement, enhances power and economy by reducing detonation and increasing top ring temperature for better sealing and performance.

Features:

• Material: Keith Black hypereutectic alloy offers durability and heat resistance

• Design: Lightweight construction for increased power and fuel efficiency

• Bore Size: Oversized.030 to fit a 3.498-inch bore

• Compression Ratio: 8.5:1 for balanced performance and reliability

• Heat Transfer: Low heat transfer alloy keeps piston skirts cool, reducing expansion

• Ring Placement: High compression ring position improves power output and detonation resistance

• Application: Fits Harley Davidson FXR models from 1984 to 1993

• Installation: Includes instructions for proper break-in and installation

Fitment:
Harley Davidson FLST 1986
Harley Davidson FLST 1987
Harley Davidson FLST 1988
Harley Davidson FLST 1989
Harley Davidson FLST 1990
Harley Davidson FLST 1991
Harley Davidson FLST 1992
Harley Davidson FLST 1993
Harley Davidson FLST 1994
Harley Davidson FLST 1995
Harley Davidson FLST 1996
Harley Davidson FLST 1997
Harley Davidson FLST 1998
Harley Davidson FLT 1984
Harley Davidson FLT 1985
Harley Davidson FLT 1986
Harley Davidson FLT 1987
Harley Davidson FLT 1988
Harley Davidson FLT 1989
Harley Davidson FLT 1990
Harley Davidson FLT 1991
Harley Davidson FLT 1992
Harley Davidson FLT 1993
Harley Davidson FLT 1994
Harley Davidson FLT 1995
Harley Davidson FLT 1996
Harley Davidson FLT 1997
Harley Davidson FLT 1998
Harley Davidson FXD 1991
Harley Davidson FXD 1992
Harley Davidson FXD 1993
Harley Davidson FXD 1994
Harley Davidson FXD 1995
Harley Davidson FXD 1996
Harley Davidson FXD 1997
Harley Davidson FXD 1998
Harley Davidson FXR 1984
Harley Davidson FXR 1985
Harley Davidson FXR 1986
Harley Davidson FXR 1987
Harley Davidson FXR 1988
Harley Davidson FXR 1989
Harley Davidson FXR 1990
Harley Davidson FXR 1991
Harley Davidson FXR 1992
Harley Davidson FXR 1993
Harley Davidson FXR 1994
Harley Davidson FXST 1984
Harley Davidson FXST 1985
Harley Davidson FXST 1986
Harley Davidson FXST 1987
Harley Davidson FXST 1988
Harley Davidson FXST 1989
Harley Davidson FXST 1990
Harley Davidson FXST 1991
Harley Davidson FXST 1992
Harley Davidson FXST 1993
Harley Davidson FXST 1994
Harley Davidson FXST 1995
Harley Davidson FXST 1996
Harley Davidson FXST 1997
Harley Davidson FXST 1998