A new fuel injection concept called micro-pulsation fuel injection (μPFi) system had been installed in a commercial 4 stroke, 125 c.c. motorcycle engine for feasibility study. The thermal bubble inkjet technology is used on the design of digital controlled μPFi system in this study. This system is composite by the arrays of the thermal bubble micro-fuel injectors, which could be operating in high ejection frequency and with fine fuel droplets into the intake pipe on engines by accurate control mode. The advantages of digital control on fuel droplet atomization are active control of fuel ejection volume and optimization of combustion efficiency. The atomized fuel droplet volumes are controlled within 100 ∼ 500 pl. The endurance test of the μPFi fuel supply assemblage had accumulated over 200 hours in a bench. It could be afforded a motorcycle to drive more than 10,000 km accumulated-mileage at constant speed 50 kph. The engine tests show that the μPFi engine improved BSFC by up to 15%, relative to carburetor engine. In addition, the motorcycle with μPFi system achieves superior exhaust CO emissions than the carburetor system while keeping comparable performance.