In June 1999, Honda equipped Giorno Crea, a scooter for the Japanese market, with a liquid-cooled, 4-stroke, 50 cc engine that adopted the world's first idling stop system for production motorcycles.
This system was further evolved through the introduction of an ACG starter newly developed for 125cc engines to realize a virtually silent engine start.
The engine incorporates technologies to restart instantly and smoothly after an idle stop: an electronically controlled swing-back that returns the crank to the optimal position for easily restarting the engine after stopping and a decompression mechanism that mitigates cranking resistance from engine starting compression.
To reduce the friction in the valve system, we adopted shell-type needle bearings for the shaft that supports the rocker-arms and also designed these bearings for durability.
Friction loss is further reduced through a cam profile proportionate to the valve system's inertial mass, which has been lowered due to use of a smaller and lighter roller, and through the reduction of valve spring load.