Forged low compression Wiseco piston kit. 7:1 compression ration (stock is around 8:1) for improved reliability. Includes wrist pins; circlips and Hastings rings. Note: These Wiseco pistons will fit stock style Hastings rings with 1.2mm (0.047") top & middle ringlands and a 4.75mm oil ring.

High 10.5:1 compression ratio ratio with forged flat top pistons. No cylinder head modifications required. Includes Hastings rings; circlips and wrist pins.

Stock replacement forged piston kit. Stock 8.5:1 compression ratio. Complete with Hastings rings; circlips and wrist pins. Note: Will also fit Evo B.T. models equipped with Screamin'' Eagle cylinders heads; which will give a higher 9.5:1 compression ratio.

High 10:1 compression ratio (standard is 9:1) for stock XL 1000 Sportster models. Will not fit XR style cylinder heads. Incl. forged pistons; wristpins; Hastings rings and circlips.

Replacement; recessed dome; forged piston kits for used with S&S Evolution SuperStock heads only in combination with components with stock dimensions (bore 3-1/2"; stroke 4-1/4" and cylinder length 5.550"). S&S tolerance recommendations: Close fit .0015" to .002". Loose fit: .003" to .004". Will give approx. 10.1:1 CR. All pistons include wrist pins; wrist pin clips and piston rings. Note: In any and all applications the technician must be able to judge components for their suitability in combination with the other engine components; prior to installation. It is of importance that a knowledgeable mechanic will install & make adjustments as required. The rider must follow standard break-in and riding procedures for overhauled engines.

Replacement recessed dome pistons for 3-5/8" Big Bore applications. Will fit 84-99 Evolution Big Twin models with S&S SuperStock heads only and 3-5/8" bore cylinders in combination with 4-1/4" (5.375" cylinders; 9.4:1CR); 4-1/2" (5.500" cylinders; 9.8:1CR) and 4-5/8" (5.565" cylinders; 10.1:1CR) strokes. S&S tolerance recommendations: Close fit .0015" to .002". Loose fit: .003" to .004". All pistons include wrist pins; wrist pin clips and piston rings. Note: In any and all applications the technician must be able to judge components for their suitability in combination with the other engine components; prior to installation. It is of importance that a knowledgeable mechanic will install & make adjustments as required. The rider must follow standard break-in and riding procedures for overhauled engines.

11.1:1 compression ratio. Piston kit includes forged pistons; rings; wristpins and clips. Crankcases do not require boring. Big bore 4.250" cylinders are required; OEM cylinders can not be bored to 4.250". 117" to 128" pistons come with 1.0805" deck height and are compatible with the OEM 4.500" stroke. Note: See S&S 574121 (black wrinkle) or 547122 (black wrinkle with higlighted fins) for 4.250" big bore cylinders only. Note: Gaskets are sold separately as 591055 head gaskets; 591054 base gaskets or 591056 head & base gasket kit. Note: S&S recommends an S&S 550 series cam; which are available in both chain or gear drive. Note: In any and all applications the technician must be able to judge components for their suitability in combination with the other engine components; prior to installation. It is of importance that a knowledgeable mechanic will install & make adjustments as required. The rider must follow standard break-in and riding procedures for overhauled engines.

Very high 12:1 compression ratio. Racing only. Standard 3-1/2" bore; domed pistons. Includes forged pistons; Hastings rings; wrist pins and circlips. Note: See 908655 for a replacement Hastings piston ring set. Note: Oversizes are not available.

10:1 compression ratio. Will fit with stock and 101HP Thunderstorm heads. Incl. forged pistons; Hastings rings; wristpins and circlips. Note: See 912702 for the required gasket kit.

Forged high compression Wiseco piston kit. 9.5:1 compression ration (stock is around 8:1). Includes wrist pins; circlips and Hastings rings. Note: These Wiseco pistons will fit stock style Hastings rings with 1.2mm (0.047") top & middle ringlands and a 4.75mm oil ring.