Sirris F43 CMX 220mm Tool-Free LSC Fork | By Sirris Suspension | For Ventus One+

Built to Dominate Any Terrain, Any Time

At REV Rides we spend a lot of time helping riders get more out of compact e-moto platforms, and the Sirris F43 CMX Fork is one of the most serious suspension upgrades you can put on a Ventus One+. This fork brings true motocross level suspension engineering to a lightweight electric platform, giving riders a front end that feels more planted, more precise, and far more capable when speeds and terrain start getting rough.

The F43 CMX combines an oversized 43mm upside-down race chassis with Sirris’ proprietary CMX tuned closed cartridge damping system. The result is razor sharp handling, strong front end support, and the kind of confidence that lets you push harder without the fork feeling vague or overwhelmed. With 220mm of travel, tool-free compression adjustment, and race-grade construction throughout, this is a premium upgrade for riders who want real performance, not just a cosmetic change.

Sirris took their race-proven F43 platform and resized it specifically for compact e-moto bikes. The 775mm extended chassis, oversized stanchions, and billet clamps create a longer, stiffer, and more controlled front end while still keeping the bike agile. Everything about this fork was designed to reduce flex, improve balance, absorb hard hits, and deliver long-haul durability for riders who actually ride their bikes hard.

Oversized Chassis Designed to Outperform

• 43mm hard chrome stanchions resist flex, dents, and wear

• 7XXX series hard anodized uppers maximize strength and durability

• 775mm extended fork length creates a longer and more planted front end

• 220mm travel delivers 20mm more suspension travel than stock style compact e-moto forks

• Lightweight billet aluminum clamps increase stiffness and reduce twisting

• 178mm fork spacing allows nearly unlimited tire choices for dirt or street setups

• Direct mount stem compatibility improves cockpit stiffness and front-end feel

• Custom ultra stiff chromoly axle improves steering precision and predictability

• Motorcycle style top cap helps maintain more consistent steering bearing tension

• Replaceable brake caliper adapters and swappable wheel spacers allow future wheel and brake upgrades

This fork is not just stiffer. It is stronger where it matters, more controlled in hard impacts, and built to keep working lap after lap without giving up predictability.

Race Grade CMX Closed Cartridge Damping

At the heart of the F43 CMX is Sirris’ CMX tuned symmetrical closed cartridge damper. This is the most advanced damping system they have put into a compact platform. It delivers pro-level damping with separate oil paths for lubrication and damping, high-flow internals, and fully tunable compression and rebound circuits that stay cool and consistent during aggressive riding.

• CMX Compact Motocross Tune built for aggressive compact e-moto riding

• True symmetrical closed cartridge design for fade-free damping

• Independent oil circuits separate damping and lubrication oil

• High-flow pistons with fully tunable compression and rebound valving

• Hydraulic bottom-out control helps save harsh landings on big hits

• 7XXX series internal components are hard anodized to reduce wear

• Premium Daido bushings and NOK MX seals deliver smooth action and long service life

The CMX tune gives the Ventus One+ a planted, confident ride feel right from the first ride. It stays predictable when you are on the gas, and it gives riders room to tune the fork around their speed, terrain, and preference.

Tool-Free Compression Adjustment

The F43 CMX includes tool-free compression adjusters, so quick setup changes are easy without needing a screwdriver. Riders get nearly 30 clicks of external compression adjustability, making it simple to fine tune the fork for different terrain or riding styles.

Direct Mount Stem System

The Sirris steerer tube and top cap system are designed around a direct mount stem setup. This improves clamping stiffness and steering bearing torque retention, similar to what you would expect on a larger motorcycle. It is one of those design details that helps give the fork a more locked-in and confidence inspiring front-end feel.

Optional Drop Clamp for Big Wheel Builds

The optional drop clamp raises the front end an additional 25mm, extending fork length to approximately 800mm. This makes it possible to run a 21 inch front wheel while maintaining bike balance when paired with a longer rear shock or taller rear setup.

Axle and Brake Mount System

• Custom ultra stiff chromoly axle improves steering precision and predictability

• Replaceable caliper mount brackets allow brake upgrades

• Designed for 220mm brake rotor setups

• All Sirris brake brackets are designed for 220mm rotors only

Technical Specifications

• Architecture: Upside down fork

• Travel: 220 mm

• Free Length: 775 mm

• Extended Length with Drop Clamp: Approximately 800 mm

• Fork Spacing: 178 mm

• Weight: 4 kg per leg

• Stanchions: Ø43 mm high tensile steel, hard chrome

• Outer Tubes: Seamless 7050 aluminum, Type 3 hard anodized coating

• Drop Outs: 6061 aluminum, Type 2 anodized coating

• Axle: Ultra high tensile hard chromed axle

• Triple Clamps: Billet 6061 aluminum, Type 2 anodized coating, Black or Blue

• Steer Tube: Seamless 7050 aluminum, Type 2 anodized coating

• Damping: Symmetrical adjustable closed cartridge with spring backed modified IFP

• Damper Bodies: Seamless 7050 aluminum, Type 3 hard anodized coating

• Compression Adjustment: External tool-free compression adjuster

• Rebound: Dual side high tensile steel spring, adjustable, rebound adjusted using tool

• Seals: NOK MX seals

• Bushings: Daido MX bushings

• Fork Guards: High impact PP, 210-degree wraparound

Spring Rate Options

• Medium: 140 to 180 lb rider weight, 3.6 / 3.6 springs

• Heavy: 180 to 220 lb rider weight, 4.0 / 3.6 springs

Rider weight ranges are based on body weight without riding gear. Sirris factors approximately 15 pounds of riding gear into the stated weight ranges. Any heavier upgrades like a battery, controller, or other major components should also be added to rider weight when selecting spring rates.

CMX Tune Setup Notes

• Factory settings are measured in clicks from the fully closed position

• Once closed fully clockwise, back the adjusters out counter-clockwise to the recommended starting point

• Riders near a weight cutoff may need preload adjustment to dial in sag

• Very aggressive or pro riders may benefit from moving up one spring class and reducing preload

• Rider preference and terrain may require additional tuning changes

• Example: a 160 lb rider with 20 lb of added upgrades calculates to 180 lb total system weight

• Aggressive rider at 180 lb would typically lean toward the heavy tune with lower preload

• Relaxed rider at 180 lb could run the medium tune with higher preload

Fitment

• Ventus One+

Who This Fork Is Perfect For

• Ventus One+ riders building a premium race ready or track focused setup

• Trail riders who want maximum front end confidence, durability, and control

• High performance builds that need true motocross level suspension performance

Fitment: Sirris F43 CMX 220mm Fork | Tool free LSC | Ventus One + Plus

• Ventus one+ plus

This product may be compatible with more models than shown above. Please see the product description for full details, or contact us for help with fitment.