Cylinder Kit 85mm Yamaha YZ 250F 25-26 Athena P400485100112 Big Bore 304cc

Description

Big bore cylinder kit for the Yamaha YZ-F 250 cc from 2025 to 2026, designed to increase engine displacement to 304.15 cc and provide increased torque and power throughout the RPM range while retaining the motorcycle’s agility and responsiveness. The kit combines an oversized cylinder and forged piston assembly with the pre-calibrated GET Boost electronic module, providing the components required for the increased-capacity engine configuration.

Features

  • High-grade cylinder with oversized steel liner

  • Forged performance piston supplied with pin and rings

  • Includes all necessary gaskets

  • GET Boost electronic module included

  • GET Boost is pre-calibrated specifically for the big bore configuration

  • Installs without ECU or wiring modifications

  • Dedicated harness connects directly to the injector and throttle body

  • Pre-mapped power curve for safe and reliable operation with the new cylinder

  • Developed using experience from MXGP and AMA racing

  • Designed for smooth, progressive power delivery across the RPM range

  • MLS head gasket provides combustion sealing and long-term durability

Specifications

  • Bore diameter: 85.00 mm

  • Bore gain: +8 mm

  • Compression ratio: 13.3:1

  • Displacement: 304.15 cc

  • Cylinder material: high-silicon aluminium alloy

  • Cylinder liner: steel

  • Liner construction: proprietary co-casting process

  • Piston: forged and CNC-machined

  • Piston coating: molybdenum disulphide

  • Piston pin coating: DLC

  • Head gasket type: MLS (Multi-Layer Steel)

  • Head gasket material: laser-cut stainless steel

Cross-Reference OEM Part Numbers

  • Athena: P400485100112

Vehicle Fitments

  • Yamaha YZ-F 250 cc: 2025–2026

Cylinder Kit 85mm Yamaha YZ 250F 25-26 Athena P400485100112 Big Bore 304cc

Product form

Big bore cylinder kit for the Yamaha YZ-F 250 cc from 2025 to 2026, designed to increase engine displacement to... Read more

1 in stock 1-2 business days

£726.00 Incl. VAT

    • Guaranteed secure & safe checkout.

      shop pay

    SKU: 56-K250.85.KIT4
    Barcode: 0120000117901

    • Free shipping on all orders above £75
    • No hassle returns within 30 days

    Description

    Big bore cylinder kit for the Yamaha YZ-F 250 cc from 2025 to 2026, designed to increase engine displacement to 304.15 cc and provide increased torque and power throughout the RPM range while retaining the motorcycle’s agility and responsiveness. The kit combines an oversized cylinder and forged piston assembly with the pre-calibrated GET Boost electronic module, providing the components required for the increased-capacity engine configuration.

    Features

    • High-grade cylinder with oversized steel liner

    • Forged performance piston supplied with pin and rings

    • Includes all necessary gaskets

    • GET Boost electronic module included

    • GET Boost is pre-calibrated specifically for the big bore configuration

    • Installs without ECU or wiring modifications

    • Dedicated harness connects directly to the injector and throttle body

    • Pre-mapped power curve for safe and reliable operation with the new cylinder

    • Developed using experience from MXGP and AMA racing

    • Designed for smooth, progressive power delivery across the RPM range

    • MLS head gasket provides combustion sealing and long-term durability

    Specifications

    • Bore diameter: 85.00 mm

    • Bore gain: +8 mm

    • Compression ratio: 13.3:1

    • Displacement: 304.15 cc

    • Cylinder material: high-silicon aluminium alloy

    • Cylinder liner: steel

    • Liner construction: proprietary co-casting process

    • Piston: forged and CNC-machined

    • Piston coating: molybdenum disulphide

    • Piston pin coating: DLC

    • Head gasket type: MLS (Multi-Layer Steel)

    • Head gasket material: laser-cut stainless steel

    Cross-Reference OEM Part Numbers

    • Athena: P400485100112

    Vehicle Fitments

    • Yamaha YZ-F 250 cc: 2025–2026

    Shipping & Delivery

    How long will my item take to arrive?

    Orders are typically dispatched within 1 working day and are shipped on a 24hour (non-guaranteed) service.

    Where do you ship to?

    We currently only ship orders within the UK.

    How can I track my order?

    Once your order has been dispatched, you will receive a tracking code. Tracking information is emailed to the email address that was provided when placing the order.

    Can I collect my order?

    Unfortunately we do not offer order collections from our fulfilment centre.

    WHY NOT CHECK OUT

    Recently viewed products

      Sign up for our newsletter

      Subscribe to our Mailing List

      Never miss any news and be the first to know about sale and offers

      © 2026 Radhouse, Powered by Shopify

        • American Express
        • Apple Pay
        • Diners Club
        • Discover
        • Google Pay
        • Maestro
        • Mastercard
        • PayPal
        • Shop Pay
        • Union Pay
        • Visa