Sirris CMX Tune F43 Fork | Arctic Leopard XE Pro S, Enduro & Vetra Blazer

The Sirris CMX Tune F43 Fork brings motocross-level suspension technology to the Arctic Leopard XE Pro S, Enduro, and Vetra Blazer. Built for riders pushing these high-power e-motos beyond the limits of standard suspension, the F43 combines 220mm of travel, 43mm high-tensile steel stanchions, closed-cartridge damping, hydraulic bottom-out control, and billet aluminum triple clamps into a front suspension package made for serious riding.

This version of the F43 fits the Arctic Leopard XE Pro S, Arctic Leopard Enduro, and Vetra Blazer. The Arctic Leopard XE Pro R uses a different F43 fork configuration because of its brake bracket and 240mm rotor setup.

Rider Weight & Spring Options

Sirris offers two rider weight ranges when selecting the CMX Tune F43. Listed weight ranges are rider weight without riding gear. Approximately 15 pounds of riding gear is already calculated into the recommended ranges.

• 140 lbs to 180 lbs: Medium, 4.0 / 3.6 springs
• 180 lbs to 220 lbs: Heavy, 4.0 / 4.0 springs

Fork spring rates are listed as left side / right side.

Fork Specifications

• Architecture: Upside-down fork
• Travel: 220mm
• Free Length: 775mm, 800mm total length with drop clamp
• Fork Spacing: 178mm, allowing extensive dirt or street tire options
• Fork Weight: 4 kg per leg
• Stanchions: 43mm high-tensile steel with hard chrome
• Outer Tubes: Seamless 7050 aluminum with Type 3 hard-anodized coating
• Dropouts: 6061 aluminum with Type 2 anodized coating
• Brake Mounting: Sized for 220mm rotors
• Brake Bracket: 220mm rotor brake bracket included
• Axle: Custom ultra-stiff, race-grade, ultra-high-tensile hard-chromed axle
• Wheel Spacers: Arctic Leopard XE Pro S wheel spacers included
• Triple Clamps: Drop clamp, billet 6061 aluminum, Type 2 anodized coating, black
• Steer Tube: Seamless 7050 aluminum with Type 2 anodized coating
• Stem Mount: 4-bolt direct-mount stem only
• Seals: NOK MX seals
• Bushings: Daido MX bushings
• Guards: High-impact PP with 210-degree wraparound coverage

Replaceable caliper mount brackets give riders additional flexibility for future brake, caliper, rotor, and wheel upgrades.

Stem Fitment

Early Arctic Leopard XE Pro S models: Some early bikes may require a direct-mount stem because the Sirris steerer tube cannot be clamped. Sirris recommends a compatible direct-mount option such as a Warp 9 stem or the GritShift Heavy Hitter Adjustable Billet Display Mount.

Later Arctic Leopard XE Pro S models: Later bikes already use a direct-mount stem and do not require a stem upgrade. Check your bike before ordering to verify which stem configuration you have.

CMX Closed-Cartridge Damping

The F43 uses Sirris' CMX, or Compact Motocross Tune, with a symmetrical and adjustable closed-cartridge system backed by a modified spring-loaded IFP. High-flow pistons and fully tunable compression and rebound valving give riders more control over how the fork reacts to braking, repeated impacts, jumps, and rapidly changing terrain.

• Dual Oil Circuits: Separate lubrication and damping oils allow the system to further optimize high-speed and low-speed damping performance.
• High-Flow Pistons: Designed to provide consistent oil flow and a broad range of compression and rebound tuning.
• Hydraulic Bump Stop: Hydraulic bottom-out control helps provide softer landings while allowing riders to use the available fork stroke during aggressive impacts.
• Damper Bodies: Seamless 7050 aluminum with Type 3 hard-anodized coating for durability and scratch resistance.
• Rebound: Dual-side high-tensile steel spring, adjustable.
• Adjustments: External compression and rebound adjustment. Compression adjustment is tool-free, while rebound requires a tool.
• Top Cap System: Motorcycle-style top cap provides more consistent control over steering bearing tension.

Built for Hard Riding

At 4 kg per fork leg, the F43 is intentionally built around strength and rigidity rather than chasing the lowest possible weight. High-power e-motos can generate substantial braking loads and suspension forces, particularly when ridden at speed, jumped, or pushed through technical terrain. The F43's oversized construction and custom race-grade axle are designed to improve steering precision and front-end confidence under those conditions.

The 178mm fork spacing also provides plenty of room for different dirt and street tire combinations. Combined with replaceable caliper brackets, this gives riders more flexibility when building around larger tires, different wheels, or future brake upgrades.

Fitment

• Arctic Leopard XE Pro S
• Arctic Leopard XE Pro S Enduro
• Vetra Blazer

Fitment Note: This is the 220mm brake rotor version of the Sirris F43. The Arctic Leopard XE Pro R requires the separate F43 configuration designed around its different brake bracket and 240mm rotor setup.

Included wheel spacers are for the Arctic Leopard XE Pro S application. Verify wheel spacing and required hardware when installing the fork on a Vetra Blazer.

Who Is the F43 For?

• Aggressive trail and enduro riders looking for better front-end control through rocks, roots, braking bumps, drops, and technical terrain.
• Jump and track riders who need hydraulic bottom-out control and consistent closed-cartridge damping through repeated hard impacts.
• Arctic Leopard and Vetra Blazer riders building a more capable e-moto with stronger, more adjustable suspension for higher-speed and more aggressive riding.