Motorex Racing Fork Oil is a high-performance suspension fluid engineered specifically for modern cartridge, inverted (USD), and conventional open-bath motorcycle forks. Developed in direct collaboration with factory race teams and WP Suspension, this fluid is formulated to withstand the extreme thermal loads and high shear forces generated within modern tight-tolerance suspension valving. Under hard riding, rapid fluid cycling across damping shims generates friction that can break down standard hydraulic oils, resulting in air entrainment, fading rebound, and inconsistent compression damping.

The Racing Fork Oil line incorporates Motorex’s proprietary "3D Response Technology," which utilizes a specialized molecular structure designed to absorb and distribute shock and shear loads across a three-dimensional grid rather than a traditional linear plane. This formulation delivers exceptional thermal stability, resists cavitation, and ensures immediate air release to prevent foaming. Surface-active friction modifiers minimize breakaway stiction between fork sliders, internal bushings, and oil seals, providing supple initial stroke compliance and consistent front-end traction throughout extended motos and long off-road stages.

Features:

• 3D Response Technology: Three-dimensional molecular architecture absorbs high mechanical shear forces and distributes damping loads evenly across shim stacks.

• Low Breakaway Friction (Anti-Stiction): Minimizes static friction between stanchions, bushings, and wiper seals for immediate compliance over small chop and trail chatter.

• Rapid Air Release & Anti-Foam: Prevents micro-bubble aeration and cavitation across high-speed compression orifices, eliminating damping fade.

• Thermal Shear Stability: High Viscosity Index (VI) maintains uniform hydraulic resistance across broad operating temperatures.

• Elastomer Conditioning: Protects NBR and FKM oil seals against hardening, drying, and micro-cracking to prevent fork seal weeping.

• WP Suspension OEM Development Partner: Factory standard fill and recommended service fluid for WP XACT, XPLOR, and AER fork systems across KTM, Husqvarna, and GASGAS platforms.

• Fully Miscible: All viscosity grades can be intermixed in calculated ratios to produce precise intermediate weights for custom suspension tuning.

What's in the Box:

• 1x Motorex Racing Fork Oil (1-Liter / 33.8 fl oz Bottle)

• (Note: Select your required viscosity—2.5W, 4W, 5W, 7.5W, 10W, or 15W—from the variant dropdown menu before checkout).

Viscosity Selection & Application Guide:

• 2.5W: Ultra-light fluid designed for closed-cartridge competition forks, trials suspension, and lightweight riders requiring minimal hydraulic drag and fast rebound response.

• 4W: Factory OEM standard specification for modern WP XACT and AER closed-cartridge/air forks. Engineered specifically for tight-tolerance WP cartridge valving.

• 5W: Common factory replacement weight for Japanese closed-cartridge and dual-chamber forks (KYB SSS, Showa Twin Chamber). Delivers balanced, all-around valving resistance.

• 7.5W: Standard specification for European open-bath enduro forks (WP XPLOR, Marzocchi, Sachs). Provides added mid-stroke support and slower rebound control.

• 10W: Recommended for conventional damper-rod forks, street applications, and heavy dual-sport motorcycles (Suzuki DR-Z400, Suzuki DR650, Kawasaki KLR650) requiring firmer low-speed damping.

• 15W: Heavyweight damping fluid for vintage damper-rod forks, classic street bikes, or heavily loaded touring front ends requiring reduced brake dive and slower chassis pitch.

• WP XACT Damping Calibration (4W vs. 5W): On modern KTM, Husqvarna, and GASGAS motorcycles equipped with WP XACT or AER forks, always follow the factory manual callout for 4W fluid. While 5W is often treated as a universal fork oil weight, running 5W in a system valved specifically for 4W increases low-speed damping firmness noticeably. This causes sluggish rebound return over consecutive braking bumps and transfers excessive harshness into the rider's hands on square-edge rocks.

• Cartridge De-Aeration & Air Chamber Measurement: Never measure fork oil volume solely by pouring in fluid ounces or cubic centimeters from a graduated cylinder. Used forks retain oil inside cartridge valving cavities, leading to mismatched oil heights between fork legs. Always pump the inner damper rod slowly through its complete stroke 10 to 15 times until all hydraulic resistance is consistent and zero micro-bubbles emerge. Then compress the fork leg fully (without the main spring installed) and measure down from the top edge of the outer tube to the oil surface using a dedicated syringe fluid level gauge.

• Linear Miscibility for Custom Dampening: All Motorex Racing Fork Oil viscosities share the identical chemical base and additive package, allowing linear mixing. If 4W is slightly too soft on high-speed compression but 5W feels harsh, mix equal parts (50/50) of 4W and 5W to produce a precise 4.5W fluid. Similarly, a 50/50 blend of 5W and 10W yields a 7.5W fluid.