S&S, M8 114" to 128" big bore piston kit. Std
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.
The estimated dispatch time is displayed on each product page and depends on the product’s stock location:
- In stock: dispatch within 1–3 business days
- European stock: dispatch within 2–3 business days
- USA stock: estimated dispatch within 3–5 weeks
- Products with a specific lead time: estimated dispatch according to the timeframe displayed on the product page
Once your order has been dispatched, you will receive a confirmation email with tracking information.
Estimated carrier transit times are:
- France: 1–5 business days
- Most European destinations: 5–10 business days
- Countries outside the European Union: delivery times may vary depending on the destination and customs clearance
The dispatch estimate and carrier transit time are separate.
Compatibility
You can verify compatibility in two ways:
- Use the vehicle selector on the product page to check whether the part matches your motorcycle.
- Review the fitment table for the full list of compatible models and years.
Some parts may require additional components, modifications or a specific existing setup. Always read the fitment notes and product description before ordering.
Still unsure? Contact us with:
- motorcycle make and model;
- model year;
- exact version or trim;
- current modifications;
- product reference or link.
Our team will help you confirm compatibility before ordering.
Eligible items may be returned within 30 days of delivery.
To be accepted, the item must be:
- unused and uninstalled;
- in its original condition;
- returned with its original packaging, labels and accessories.
Parts that have been installed, damaged or modified cannot be returned.
Please contact us before sending an item back. Returns sent without prior authorization may not be accepted.
Return shipping costs remain the customer’s responsibility unless the item received is incorrect, damaged or defective.
Customs Duties & Taxes
European Union
Orders delivered within the European Union are shipped from France. No import duties are charged upon delivery.
Countries outside the European Union
Local VAT, customs duties and carrier clearance fees may apply. These charges are determined by the destination country and remain the customer’s responsibility.
Payment Options
We accept major credit and debit cards, PayPal and the installment payment methods displayed at checkout.
Eligible orders may be paid in 3 or 4 installments, subject to the payment provider’s approval and applicable limits.

