The Sirris F43 CMX fork brings full-size suspension construction and adjustable closed-cartridge damping to the Surron Light Bee X. With 43mm stanchions, 220mm of travel, and CMX (Compact Motocross) tuning, it delivers the support and control needed for aggressive riding.
High-flow internals and fully tunable compression and rebound circuits let you dial in the fork for your riding style, while a hydraulic bump stop provides progressive bottom-out control for hard impacts and landings.
Designed for the Light Bee X, the F43 includes LBX wheel spacers and a 220mm rotor brake bracket. Installation requires a 220mm front brake rotor and a compatible four-bolt direct-mount stem. The stock LBX 200mm rotor and stem are not compatible.
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Key Features
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CMX Tune: Compact Motocross tuning with fully tunable compression and rebound valving for aggressive riding.
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Full-size construction: 43mm hard-chrome steel stanchions and sturdy aluminum outer tubes provide strength and steering precision.
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220mm of travel: Adjustable suspension with a hydraulic bump stop for progressive bottom-out control and softer landings.
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Symmetrical closed-cartridge dampers: Both legs use pressurized dampers with spring-backed modified internal floating pistons for balanced, consistent, fade-resistant performance.
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Dual oil circuits: Separate lubrication and damping oils allow optimized damping performance.
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External adjustments: Tool-free compression adjustment and tool-operated rebound adjustment.
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Upgrade flexibility: Replaceable caliper mount brackets accommodate brake and wheel upgrades, while 178mm fork spacing provides clearance for a wide range of dirt and street tires.
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Optional drop clamp: Adds 25mm of extended length and allows for a 21-inch front wheel conversion.
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Quality seals and bushings: NOK MX seals and Daido MX bushings support smooth operation and durability.
Rider Weight and Spring Selection
Sirris offers two weight ranges when selecting your CMX Tune F43 fork. Select your spring option based on rider weight without riding gear. Sirris already accounts for 15 lbs of riding gear in the ranges below.
Fork spring rates are listed as left side / right side.
| Rider Weight Without Gear |
Spring Option |
Springs — Left / Right |
| 140–180 lbs |
Medium |
3.6 / 3.2 |
| 180–220 lbs |
Heavy |
3.6 / 3.6 |
Specs
F43 CMX Tune Specifications
| Specification |
Details |
| Fitment |
Surron Light Bee X (LBX) |
| Tune |
CMX — Compact Motocross |
| Architecture |
Upside-down fork |
| Travel |
220mm |
| Free Length |
775mm; optional drop clamp adds 25mm of extended length |
| Fork Spacing |
178mm |
| Fork Weight |
4 kg per leg |
| Stanchions |
Ø43mm, high-tensile steel with hard chrome |
| Outer Tubes |
Seamless 7050 aluminum, Type 3 hard anodized |
| Dropouts |
6061 aluminum, Type 2 anodized, with replaceable caliper mount brackets |
| Brake Mounting |
Sized for 220mm rotors; 220mm rotor brake bracket included |
| Axle |
Custom ultra-high-tensile, hard-chromed axle; LBX wheel spacers included |
| Triple Clamps |
Billet 6061 aluminum, Type 2 anodized; blue or black |
| Optional Drop Clamp |
Black only; allows for 21-inch front wheel conversion |
| Steer Tube |
Seamless 7050 aluminum, Type 2 anodized |
| Stem Mount |
Four-bolt direct-mount stem only |
| Top Cap System |
Motorcycle-style top cap for consistent steering bearing tension adjustment |
| Damping |
Symmetrical, adjustable closed cartridges with spring-backed modified IFP, high-flow pistons, and fully tunable compression and rebound valving |
| Oil Circuits |
Separate damping and lubrication circuits |
| Bottom-Out Control |
Hydraulic bump stop |
| Damper Bodies |
Seamless 7050 aluminum, Type 3 hard anodized |
| Springs |
Dual-side high-tensile steel springs, adjustable |
| Adjusters |
External tool-free compression adjustment and tool-operated rebound adjustment |
| Seals |
NOK MX seals |
| Bushings |
Daido MX bushings |
| Guards |
High-impact PP, 210-degree wraparound |
Fitment
Note:
Requires a 220mm front brake rotor. The stock 200mm LBX rotor must be replaced.
Requires a compatible four-bolt direct-mount stem. The stock LBX stem is not compatible because the Sirris steerer tube cannot be clamped. Sirris recommends Warp 9 or the GritShift Heavy Hitter Adjustable Billet Display Mount.
If you are planning to run a 21-inch front wheel, please select the optional drop clamp.
