The company, based in the Santa Cruz area, has 31 employees, has shipped 40 bikes since April and has back orders for an additional 60.
Among his customers is Google Inc. founder Larry Page, who bought three Zero X bikes.
Zero is setting up a second production line to meet demand. Saiki anticipates selling 500 motorcycles next year, both for the dirt and the street. He figures to be doing $100 million in business by 2011.
"I don't expect a lot of competition," the 41-year-old Saiki said. "It takes a lot of sophistication to get a manufacturing operation started."
The motocross category is, in many ways, the perfect application for an electric power plant because motocross bikes are ridden for only a few dozen miles at a time and battery-powered motors are typically limited in their range.
The whisper-quiet operation in the hills also won't offend nearby residents.
Electric motors are pure torque machines, which is what a motocross bike needs to launch into jumps and power out of corners. The Zero X can get to its top speed of 57 mph in about four seconds.
One potential downside to an electric application in a dirt bike is the weight of the batteries, a problem Saiki chose to tackle with a feather-light, aircraft-grade aluminum frame and lithium ion batteries.
Those batteries have a greater power-to-weight ratio than the nickel metal hydride devices used in the Toyota Prius and the Vectrix scooter.
Though comparable in performance to a gas-powered, 250-cubic-centimeter motorcross bike, the Zero X is 80 pounds lighter. The entire bike weighs an unheard-of 140 pounds, only 40 of which are the batteries.