Harley-Davidson FAT BOY Big Bore Kits
Genuine HD big bore kits and aftermarket alternatives that fit the FAT BOY — all years. Select your year for exact fitment and pricing.
Select your year for exact fitment & prices
Genuine Harley-Davidson (9)
Genuine Harley-Davidson
3-7/8" Standard Bore Piston Kit
22144-08B
Genuine Harley-Davidson
Screamin' Eagle 4-Inch Big Bore Conversion Kit
92500039
Genuine Harley-Davidson
Big Bore Head Gasket Kit
16101-01
Genuine Harley-Davidson
Screamin' Eagle 103 Stage IV Performance Kit
27516-08F
Genuine Harley-Davidson
Screamin' Eagle MVA CNC Ported Cylinder Heads
16925-11
Genuine Harley-Davidson
Flat-Top Cast Pistons, 3-7/8" Std Bore, 1550cc
22851-99A
Genuine Harley-Davidson
Screamin' Eagle 110CI Stage III Upgrade Kit
92500035
Genuine Harley-Davidson
Screamin' Eagle 4-3/8 Inch Stroker Flywheel Assembly
23727-07A
Genuine Harley-Davidson
High-Compression Piston Kit, 4.060", Standard Bore
22574-10Aftermarket alternatives
Aftermarket big bore kits that fit the FAT BOY. Genuine Harley-Davidson is listed above, not here.
S&S Cycle
S&S 131CI & 136CI BIG BORE STROKER CYLINDERS FOR MILWAUKEE EIGHT
S&S Cycle
S&S 131CI & 136CI BIG BORE STROKER CYLINDERS FOR MILWAUKEE EIGHT
S&S Cycle
S&S 4.32" BIG BORE KITS FOR MILWAUKEE EIGHT
S&S Cycle
S&S 4.32" BIG BORE KITS FOR MILWAUKEE EIGHT
S&S Cycle
S&S BIG BORE GASKETS FOR MILWAUKEE EIGHT
S&S Cycle
S&S 131CI & 136CI BIG BORE STROKER CYLINDERS FOR MILWAUKEE EIGHT
S&S Cycle
S&S 131CI & 136CI BIG BORE STROKER CYLINDERS FOR MILWAUKEE EIGHT
V-Twin
3 5/8" BIG BORE CYLINDERS AND PISTONS FOR EVOLUTION BIG TWIN
V-Twin
3 5/8" BIG BORE CYLINDERS AND PISTONS FOR EVOLUTION BIG TWIN
S&S Cycle
HIGH COMPRESSION 132CI & 136CI BIG BORE KITS
S&S Cycle
S&S 4.32" BIG BORE KITS FOR MILWAUKEE EIGHT
S&S Cycle
S&S BIG BORE KITS FOR MILWAUKEE EIGHT