During the second half of the 1970's, small motor bikes and scooters became the rage all over Japan, as they were found to be convenient for travel in and around the congested cities. Many of the owners of these small bikes moved up to larger cc machines and have become interested in the sport of active competition. One racing event is the Tourist Trophy class of endurance racing, and the TT-F3 races are conducted with 250cc two stroke and 400cc four stroke machines, as their performance capabilities are about equal. In Japan, this class of racing is very popular due to the licensing restrictions in the country, and the major bike manufacturers are continuously competing for this market.
The Honda CB400F was unveiled at the Tokyo Motor Show in late 1983 and has become very popular for the TT-F3 racing events. Using a unique and patented system called "Revolution Modulated Valve Control", this production bike is ideally suited for TT racing. Using four valves per cylinder, this parallel four cylinder DOHC engine is designed to utilize only two valves per cylinder at lower RPM's, where most of the street running occurs, but automatically converts to 4 per cylinder at RPM's above 8200, where most racing is done. Using the engine oil pressure as the force to activate the system, a pin is inserted into two of the cam lobes per cylinder, activating all four valves at the higher RPM's. This system was developed to combat two opposing problems.
Enough torque at lower speeds and more power at the higher RPM's During competition, a simple mechanical adjustment locks out the system so that all four valves per cylinder are in operation at all RPM's. The engine is mounted in a square steel tubing double cradle frame. Honda's original Pro-Link suspension is used at the rear and their TRAC system with anti nose dive function at the front. Braking is through a triple disc system using dual piston calipers. The headlamp is mounted to the frame, with the oil cooler directly below it. Many racing, tune up parts have been made available for the fans and this has stimulated the other manufacturers to produce machines of a similar concept for TT-F3 racing, as this event continues to grow and mature.
