The Honda CB400SF (SuperFour) was discontinued in October 2022. The CB400SF was introduced in 1992, when naked bikes were at the height of their popularity, and was said to be the bike that “you can never go wrong if you choose the CB400SF” and “it was the right choice! It was the “right choice! The CB400SF was so easy to handle, and at the same time, it had a reputation for its high cornering performance. The CB400SF was also a popular choice for naked races held on race circuits at the time.

　In 1994, a new category, “NK4 (Naked 400),” was created as the Suzuka NK4 Series in conjunction with the Suzuka Championship Suzuka Sunday Road Race. The “Suzuka Constructors Committee” consisting of 12 leading constructors, of which the former Technical Sports Racing (TSR) also played a leading role, planned the races, and the regulations were designed to ensure equal conditions and low costs, not to be manufacturer-driven. The committee was started to reflect the opinions of entrants in the regulations, and to enable the committee to sell racing parts and aftermarket parts and continue the race at a profit.

　TSR entered this new category with the Honda CB400SF and showed its ability without regret, winning three consecutive victories from the opening round. This category also included a 4-hour endurance race, and the Suzuka 4 Hours (SP4 endurance at that time) and the Naked 400 SUZUKA 4 Hours (NK4 endurance) was held. Series leader TSR, the organizer and entrant, entered the race as a representative of the Suzuka team, aiming only for victory. Unfortunately, the result was a disappointing “Pole to 2nd place,” and they were beaten to the finish by the Kanto team. Nevertheless, they won the first NK4 championship in the series.