Electric Dirt and Street Motorcycles Make Debut

The fumes and ear-splitting whine of a 250cc two-banger that have long been part of dirt biking’s allure are about to be replaced by silence and zero emissions.

Quietly sleuthing through the woods, Zero Motorcycles’ new Zero X dirt bike is powered by an electric motor and lithium-ion battery (see video). From all indications, there are few riding compromises between the Zero X and its gas-powered brethren. The bikes are particularly appealing in California where development has encroached on once-secluded bike trails where noise was not an issue.

Indeed, electric motorcycles could be a trend. Brammo Motorsports LLC of Ashland, OR has the stylish 'Enertia' Electric Motorcycle under development. At 280 lbs, it’s a street bike with twice the heft of the Zero X, but at 35-45 miles about the same range. The motorcycle uses a lithium-phosphate battery made by well-known battery maker Valence Technology in Austin, TX.    

As for the dirt bike’s irritating whine, good riddance, says Zero CEO Gene Banman.

“Everybody hates the sound of off-road [gas] motorcycles. They’ve been shut down due to noise,” he says. “Some riders have backyard tracks and almost can’t use them because neighbors call the cops on them.”

The major challenge in building this alternatively-powered motorcycle, says Zero founder and Chief Technology Officer Neal Saiki, was handling the thermal problem when joining 168 battery cells in arrays. Anything more than air cooling would have jacked the bike’s weight above its svelte 140 lbs, about 100 lbs less than a Yamaha 250cc WR250F.

“We buy off-the-shelf battery cells and link them via a highly conductive inter-connector that is mechanically attached. A lot of the heat is generated in the connector joint itself, but there is no overheating there. The inter-connects handle a continuous capacity of 300 amps, which if applied would tear the rubber off the tires. To let you how much 300 amps is, we weld the frame at 220 amps,” says Saiki, an aeronautical engineer who once worked for NASA researching high-altitude research aircraft. In college, he co-developed human-powered helicopters known as the Da Vinci III and IV.

“The battery is like a microprocessor when you make them smaller. It does not have enough circuit area for cooling. Solving that same that problem was the big hurdle,” he says.

The battery, which goes by the name ZENERGY and has 168 cells, is rated at 2 kHw (58V at 35 A-hr). What's more, Zero claims the battery’s avoidance of heavy metals such as cobalt, nickel, lead or mercury makes it non-toxic. The lithium is bound by salt instead of a heavy metal, Saiki says. A full recharge takes under two hrs, according to Zero’s website.

Beyond that, Saiki won’t say much about what’s in the battery or what materials are used in the inter-connects, claiming the patent-pending inter-connect technology is proprietary and Zero may license it to other bike or parts makers. The pending patent at this point is not public. “That’s our trade secret,” he says.

The motor, an off-the-shelf permanent magnet DC unit, delivers around 20 hp.

Zero has made 37 motorcycles so far, 25 of which have been distributed to professional riders who can test them. Saiki says the company has sufficient parts on hand to build 75 more at its Santa Cruz, CA plant with plans to build a total of 500 this year.

According to one tester, there are only a few minor tradeoffs to the Zero X, although he’s not putting his gas bikes on Craig’s List just yet.

“Zero is like the sweetest thing around if you’re into not bugging people and you want instant power. [Gas bikes are] loud and the neighbors were not all that stoked about it,” says Mike Weir, a professional bicyclist who lives in Novato, CA. “Now they can’t hear it and they don’t really care anymore. Everyone thinks electric is kind of weak. This thing pops a wheelie when you get on it. It’s like nothing else.”

With a gas bike, he could hear the engine and gears changing and could gauge how fast he was going. “With an e-bike (Weir's term for the Zero), there are no gears. It’s so instant,” he says.

The other difference is battery life, although it isn’t bad at 1-2 hrs, depending on how hard the bike is pushed. Weir says he would not take it out on a 70-mile, half-day jaunt (Zero lists the bike’s range at 40 miles, adding up to 20 miles out and 20 miles back) into the woods. “You can’t do endless hill climbs because the battery won’t last that long,” he says. He admits once he had to walk home a half mile after his Zero X ran out of juice. “I didn’t mind,” he says.

And he would like to see the bike and its suspension refined as it evolves.

“Electric bikes are going to require more tweaking. You have to get your body used to it. It’s in the infancy phase and is only going to get better. But there’s still a need for gas bikes. Not everyone is going to have an e-bike. They have a ways to go to make the gas world understand how good they are.”

Zero claims the bike costs under a penny a mile to run, which translates to 40 cents for 2 hrs of tearing through the woods. Saiki concedes higher speed to gas bikes, but says the Zero X blows stink pots off the line. It can go from 0-30 mph in under two sec with its electric motor always delivering 100 percent torque. However, at that pace, staying on the bike would be a challenge.

The bike has two speed-control switches to limit the top speed to a "motorized bicycle" legal 30 mph and another switch that sets acceleration from a beginner "easy" mode to a “wheelie-popping sport" mode.

The Zero X costs $7,500, which is about $1,000 more than a 250cc gas dirt bike, according to Saiki. Indeed, a 250cc Yamaha WR250F lists for $6,399. That said, Yamaha has dirt bikes that list as low as $1,149, such as the PW50 49cc model.

The real test will be whether the bikes in mass production stand up over the long term. Saiki thinks they will. “Riding in the dirt is hard on internal combustion. This one you just use,” he says, adding a “Supermoto” street-ready version with lights and turn signals will be introduced later this year.