INNTECK KYB Shock Spring for YAMAHA WRF 250, WRF 450, YZF 250, YZF 450 and FANTIC XEF 250, XEF 450, XXF 250, XXF 450 2018-2027

The INNTECK KYB shock spring is designed for YAMAHA WRF 250, WRF 450, YZF 250, YZF 450 and FANTIC XEF 250, XEF 450, XXF 250, XXF 450 from 2018 to 2027. The shock spring carries the rear of the bike and the rider. Its spring rate must match your riding weight with gear: with the right spring, sag can be set without pushing the preload to extremes and the rear end keeps its traction.

Specifications

• Brand: INNTECK
• Manufacturer part numbers: QS3440, QS3442, QS3444, QS3446, QS3448, QS3450, QS3452, QS3454, QS3456, QS3458, QS3460, QS3462, QS3464, QS3466
• Diameter: 64/66 mm, length: 275 mm
• Available versions: 40 N/mm: ref. QS3440; 42 N/mm: ref. QS3442; 44 N/mm: ref. QS3444; 46 N/mm: ref. QS3446; 48 N/mm: ref. QS3448; 50 N/mm: ref. QS3450; 52 N/mm: ref. QS3452; 54 N/mm: ref. QS3454; 56 N/mm: ref. QS3456; 58 N/mm: ref. QS3458; 60 N/mm: ref. QS3460; 62 N/mm: ref. QS3462; 64 N/mm: ref. QS3464; 66 N/mm: ref. QS3466

Choosing the right spring rate

First set the rider sag to the manual's value using the preload collar, then measure the static sag (bike without rider): if it is too small, the spring is too soft for you; if it is too big, it is too stiff. Then change the spring rate by one or two steps.

When to replace it?

• Impossible to get the right rider sag without tightening or loosening the preload a long way.
• The rear end bottoms out often or squats under acceleration: spring too soft.
• The rear end bounces and lacks traction: spring too stiff.
• You weigh clearly more or less than the standard rider the manufacturer designed for.

Spring rate is given in N/mm (1 kg/mm is about 9.81 N/mm). Check the shock type (KYB, SHOWA, WP with linkage or WP PDS, which has no linkage) and the dimensions: the diameter and length must match your shock.

Fitting tips

1. Remove the shock as described in the manual, with the bike supported so the rear wheel is off the ground.
2. Back the preload off completely, remove the spring seat and change the spring.
3. Refit the shock to the specified torque, then set the rider sag with the preload.
4. Rebalance the fork afterwards if needed: a higher or lower rear end changes how the front end behaves.

Spare parts and items to plan

• Shock rebuild kit : PROX 26.310016 · PROX 26.450015
• Linkage bearings : ALL BALLS · FACTORY LINKS

Frequently asked questions

Who is a progressive spring for?
Its rate increases as it is compressed: soft at the start of the travel for comfort, firmer toward the end of the travel to resist bottoming out. It is mainly used on WP PDS shocks, which are fitted without linkage.

Compatibility

Check the exact model and year of your bike in the list below before ordering.

Fits:
FANTIC XEF 250 2027
FANTIC XEF 250 2026
FANTIC XEF 250 2025
FANTIC XEF 250 2024
FANTIC XEF 250 2023
FANTIC XEF 250 2022
FANTIC XEF 250 2021
FANTIC XEF 450 2027
FANTIC XEF 450 2026
FANTIC XEF 450 2025
FANTIC XEF 450 2024
FANTIC XEF 450 2023
FANTIC XXF 250 2027
FANTIC XXF 250 2026
FANTIC XXF 250 2025
FANTIC XXF 250 2024
FANTIC XXF 250 2023
FANTIC XXF 250 2022
FANTIC XXF 450 2027
FANTIC XXF 450 2026
FANTIC XXF 450 2025
FANTIC XXF 450 2024
FANTIC XXF 450 2023
FANTIC XXF 450 2022
YAMAHA WRF 250 2027
YAMAHA WRF 250 2026
YAMAHA WRF 250 2025
YAMAHA WRF 250 2024
YAMAHA WRF 250 2023
YAMAHA WRF 250 2022
YAMAHA WRF 450 2027
YAMAHA WRF 450 2026
YAMAHA WRF 450 2025
YAMAHA WRF 450 2024
YAMAHA WRF 450 2023
YAMAHA WRF 450 2022
YAMAHA YZF 250 2027
YAMAHA YZF 250 2026
YAMAHA YZF 250 2025
YAMAHA YZF 250 2024
YAMAHA YZF 250 2023
YAMAHA YZF 250 2022
YAMAHA YZF 250 2021
YAMAHA YZF 250 2020
YAMAHA YZF 250 2019
YAMAHA YZF 450 2027
YAMAHA YZF 450 2026
YAMAHA YZF 450 2025
YAMAHA YZF 450 2024
YAMAHA YZF 450 2023
YAMAHA YZF 450 2022
YAMAHA YZF 450 2021
YAMAHA YZF 450 2020
YAMAHA YZF 450 2019
YAMAHA YZF 450 2018