Ottawa police say they are cracking down on what are called pocket bikes, tiny motorcycles from China that have become a cult favourite in the city because of their cheap price tag.

Police and safety experts say they don't belong on the roads.

The tiny bikes are powered by a chainsaw motor, and can hit 50 km/h in just seconds.

"They are quite a fad in many parts of the country, and shouldn't be on roads or sidewalks," says Emile Therien of the Canada Safety Council. "Certainly children shouldn't ride them, and they are being marketed to young kids, and one dealer … markets them for three-year-olds. They are a public-safety problem."

Safety officials say the bikes are so low they can't be seen by other drivers, and should only be ridden on private property.

Last year, if Ottawa police spotted you riding the bikes on roads or sidewalks, you'd get a warning. This year, you'll get a ticket.

"They are subject to the same rules as other vehicles under the Highway Traffic Act and the Auto Insurance Act. This year, we will lay charges. They are not toys. They are not allowed on roadways," says Staff Sgt. Rick Lavigne, of the Ottawa Police Service.

The biggest fine that could be levied would be $5,000 for driving the bike without insurance.

André Derouchie, one of three pocket-bike dealers in Ottawa, agrees that they are not safe for roads. He has customers sign an agreement to that effect. But, he says, the bikes are selling like hotcakes.

"These are a great hit coming on in [the] U.S. and Canada last year. Who is buying? Kids from 14 to kids up to 40 years old," Derouchie says.

Chris Lows, who has test-driven the bikes, says they're compelling because of their manoeuvrability and speed.

"It's pretty quick once you get topped out. Then they don't go higher. But it gets there pretty quickly," Derouchie says.

Pocket bikes range in price from $400 to $1,500.