AER35 KTM 50 / 65 SX Air to Spring Conversion Kit – OEM Cap Version

Consistent feel. Predictable performance. Original fork cap retained. The Krooztune WP35 ATS (Air to Spring) OEM Cap Kit replaces the OEM air cartridge with our coil spring system while retaining the original air fork cartridge cap. Developed for USA racers who need to retain the OEM fork cap under their race rules, this version delivers the same spring performance and hydraulic bottoming control as our externally preload-adjustable ATS kit, with spring preload set internally during assembly. Fits: 2026-on KTM, Husqvarna and GASGAS 50cc and 65cc models equipped with WP35 air forks. OEM cap. Krooztune spring performance. Our purpose-made adaptor allows the original air cartridge cap to fit directly to the Krooztune ATS assembly. The cap is easily transferred using a 27 mm clamp set. Spring preload is set internally during the build, just as it is in a conventional full-size fork setup. This version has no external preload adjuster; changes to preload are made internally. It is also an option for riders outside the USA who prefer to retain the original fork cap and $100 AUD cheaper! Spring selection — 50cc The WP35 ATS 50cc Kit is supplied with one replacement spring, selected to suit the rider’s weight. This spring is installed in the air cartridge leg and works in conjunction with the OEM spring retained in the damping leg, creating the correct combined spring rate for the rider. Three spring options are available, with the appropriate spring selected at the time of purchase. Rider weight / level ATS spring option Under 22 kg .18 Under 25 kg .20 Over 25 kg / Pro riders .24 Spring selection — 65cc The WP35 ATS 65cc Kit is supplied with a matched pair of fork springs, selected to suit the rider’s weight and ability. One spring is fitted to the ATS cartridge, while the second replaces the OEM spring in the damping leg. Exchanging the damping-leg spring requires removal of the fork cap. Rider weight / level Spring pair option 25–30 kg .26 pair 30–35 kg, or expert riders over 25 kg .28 pair 35–40 kg .30 pair Heavier riders, or expert riders over 35 kg .32 pair Straightforward installation Designed as a bolt-in replacement, the WP35 ATS Kit installs with no machining or permanent modifications required. Remove the original air cartridge, transfer the OEM cap onto the Krooztune assembly using our adaptor, set the internal spring preload and install the completed assembly. For 65cc models, fit the supplied matching spring into the damping leg to complete the conversion. Consistent feel from the first lap to the last Air fork feel can change with temperature and pressure. The WP35 ATS coil spring system delivers predictable spring performance without the need to monitor air pressure. Riders benefit from smoother initial movement, improved front-end feel and increased confidence through braking bumps, ruts and rough circuits. Race-developed hydraulic bottoming control At the heart of the system is our race-developed hydraulic bottoming control, engineered to progressively increase damping during the final portion of the fork stroke. Similar in concept to systems used in modern full-size race forks, it provides increased bottoming resistance during heavy landings and large impacts while maintaining plushness throughout the majority of the travel. This allows the fork to remain compliant over small bumps while delivering the support needed when riders push harder or encounter the oversized obstacles that 50cc and 65cc bikes regularly face. Internally set spring preload Spring preload is set during assembly to establish the required setup for the rider and selected spring rate. Combined with our range of spring options, this provides the foundation for a balanced front end while retaining the OEM cap. Preload adjustment requires access to the internal assembly; there is no external preload adjustment on this version. Features Coil spring conversion retaining the OEM air fork cartridge cap Purpose-made Krooztune cap adaptor OEM cap transferred using a 27 mm clamp set Spring preload set internally during assembly Race-developed hydraulic bottoming control for increased end-stroke support Plush small-bump compliance with progressive bottoming resistance Consistent spring performance with no air pressure to monitor Improved front-end traction, balance and rider confidence Bolt-in installation with no machining or permanent modifications 50cc kit supplied with one ATS spring, retaining the OEM damping-leg spring 65cc kit supplied with a matched pair of springs Springs selected to suit rider weight and ability at the time of purchase Also available as a cartridge-only kit for customers sourcing their own springs Part of the Krooztune Flow Range Designed to work alongside the Krooztune Flow Kit and Shock Flow Kit, the WP35 ATS OEM Cap Kit forms part of the complete Krooztune Flow Range—a suspension system developed specifically for the latest generation of WP35-equipped KTM, Husqvarna and GASGAS mini bikes. From a first race bike to national-level competition, enjoy Krooztune coil spring performance and hydraulic bottoming control while retaining your original fork cap.