The 25-year-old French rider, who was second in the British MX1 championship, was preparing for a charity race in Cassel.
European Racing Manager for Kawasaki, Steve Guttridge, added to the many tributes saying:
“The number of current and former riders in both motocross and other forms of two-wheeled sport that paid tribute to Steven is a glowing testament to how popular he was personally and professionally. His passing is a sad loss to motocross and Kawasaki sends its deepest condolences to his family and friends.”