Pocket bikes are miniature motorcycles -- powered, for the most part, by oil- and gas-burning engines similar to those used in chain saws, weed whackers or other small motorized tools -- and they look just like the real thing.

The snazziest models cost thousands and are made in Italy, but the ones that are selling by the container load run from $200 to $500. They come from China, among other places, and are getting snapped up by eager teenagers and, in some cases, not-so-teenagers.

At Broadtek LLC, a South San Francisco firm that imports them, the cardboard cartons containing the small bikes are stacked to the ceiling of a tall warehouse and are quickly going out the door to eager customers.

In Walnut Creek, Eric Rahin, owner of Sonic Scooterz, says he's selling them in droves -- "from college students to people in their late 50s. It's basically a toy to have some fun with."

Manufacturers say the bikes are supposed to be used only on closed race tracks, private roads or any other place where there are no public traffic laws and, more important, no big cars or trucks to run into you. Many buyers follow that advice.

But now you see some of these new pocket bikes zinging in and out of parking lots, up and down residential streets and, occasionally into the side of a car. And therein lies the rub.

"It's very difficult for a driver (of a car) to see one on those bikes, because of their low height," said San Francisco police Lt. Kitt Crenshaw. "We've had several accidents in the last few weeks, and people went to the hospital."

The pocket bikes have a top speed of about 35 mph, but can be souped up to go faster. They evolved from tiny but highly sophisticated racing bikes that campaign on European race tracks and are sometimes used as training vehicles for Grand Prix motorcycle racers.

The bikes are faithful imitations of popular normal-size street motorcycles, which, for marketing reasons, are faithful imitations of pure race bikes, down to the disk brakes, handlebars, chain drives, twist-grip throttles and electronic ignition.

The little bikes weigh about 50 pounds, stand about a foot and a half high and can easily be put in the trunk of a car. They have tiny engines -- 47cc or 49cc displacement, less than 1/20th the size of a big motorcycle. And they are enticing.

"It's a fun little thing to ride," said Matt Damon, a 21-year-old salesman in a Martinez pet store. "It's a whole lot cheaper than a $6,000 or $7,000 big bike. For years now, I've been riding different types of motorcycles, but it's more like the small bikes are a fun thing, instead of just transportation. And it's easier to maintain and burns less gas."

But Damon did admit, "I took it for a ride down the street and got pulled over. The officer was kind of nice about it. But I got a ticket."

Police departments in the Bay Area and elsewhere in California have been cracking down on the little two-wheelers, saying they are a major accident waiting to happen. No police agency could come up with information about any deaths caused by pocket bike crashes, but police want them off the public roads before the inevitable happens.

"Their numbers are starting to increase," said Milpitas police Officer Jay Johnson, who was assigned by his department to look into the phenomenon and ultimately write about it for the weekly Milpitas Post. "Most of the complaints we're getting is that drivers can't see them or there'll be a group of them racing, or they're running stop signs."

For a while, though, until Johnson began studying up on the subject, and the California Highway Patrol sent out a memo clarifying just what is and what is not legal about the bikes, confusion seemed to be paramount.

In fact, it shouldn't be. On many bikes, there's a decal right there on the gas tank that says these things do not conform to "federal motor vehicle safety standards."

After a lengthy consult with the state Vehicle Code and the Department of Motor Vehicles, the CHP explained that the bikes do not meet a number of standards required for all vehicles registered in California -- the most telling example being the stipulation that "headlamp height (be) between 22 and 54 inches."

Technical problems aside, it's the safety issue that concerns authorities.

"We're really concerned about these things mixing with traffic," said CHP spokesman Steve Kohler. "If you think about it, something that small is difficult to see, when it's mixed in with cars, trucks and buses. Drivers don't even see full-size motorcycles. There's no way they're going to see these things."

Or, as David Edwards, editor in chief of Cycle World Magazine and a man who puts about 20,000 miles a year on motorcycles, said: "When you get out in city traffic, you'll be at more risk than on a full-size motorcycle. But they only hold (a little) gas, so you won't go too far. And they're noisy as hell, so at least people will hear you coming if not see you coming."

- Michael Taylor, Chronicle Staff Writer Wednesday, June 16, 2004