S&S, M8 131" big bore cylinder & piston kit. Black fins

Description

2151cc kit. Black powder coated wrinkle finish cylinders with black (non-highlighted) fins. Kit includes a forged 4.250" big bore piston kit, black wrinkle 4.250" big bore cylinders, 2 multi-Layer-Steel .030" head gaskets, 2 cylinder base gaskets, 4 cylinder dowels, 2 exhaust gaskets and an S&S cubic inch cam cover batch. Works with stock crankcases, case boring is not required. 4-5/8" stroker flywheels are required, these must be purchased separately as 923270 or 923271.

Note: S&S measured 146.62HP and 145TQ with a 590 cam, CNC heads, Big Bore throttle body and a high flow Stealth air cleaner kit.
Note: Fully assembled 4-5/8" stroke stroker flywheel assemblies are required for installation of this big bore kit. Available as 923270 (with balancer gear installed) or 923271 (without balancer gear). Both come with full width wrist pin connecting rods, which is required for S&S pistons.
Note: S&S 576972 extra strong head bolt kit or similar must be purchased separately.
Note: Tuning of fuel injection and ignition is required.
Note: S&S does not advise this kit for use on any Tri-Glide or other three wheelers, including conversions, due to the lugging nature of these bikes.

Specifications

Fitment

17-25 M8 models (excl. 2025 Softail; 23-25 CVO; 24-25 FLTRX; 24-25 FLHX; 2025 FLHXU; all Trikes) (NU)

Part numbers