Just because you can put a motor on it doesn't mean you should put a motor on it.
Authorities are warning enthusiasts that a craze of motorising vehicles from bikes to scooters to "drift trikes" could run foul of the law.
A group of "motor drift trike" riders - low-slung tricycles with special sliding rear wheels and retro-fitted motors - have uploaded videos of their exploits to a Facebook page called "Slid3wayz".
Several of the videos show the bikes sliding through schools and car parks, though it is the ones filmed on roads that have drawn concern.
New Zealand Transport Agency spokesman Andy Knackstedt said the short answer was that "all of these things look to be motor vehicles, and as such would need to be registered and licensed to be legally used on a public road".
Police national road policing manager Superintendent Carey Griffiths said police took a "common sense" approach but "anyone using any vehicle [including drift trikes] in an unsafe manner may face prosecution for careless use".
Waiuku man John Mann has been importing kits for motorising bikes for more than 20 years, but he said they were used as "engine- assists" rather than as the principal power of the bike.
Riders pedalled and then dropped the clutch on the two- stroke engine to assist in coasting.
His company Motrax had sold kits all over the country. They were popular in the South Island but not so popular in Wellington and Auckland, he said.
His customers were varied and included older people who lacked fitness and people who had lost their licence.
He said the law was something of a "grey area" when it came to revving up your pushbike.
Police sometimes classed the bikes as mopeds but only a handful of his clients had registered their bikes.
One rider had gone to police and obtained a certificate to say his kit was strictly for "pedal assistance", Mann said.
Hamilton man Paul Chin has built several motorised bikes over the years. When he sells his bikes he is sure to let buyers know it is an "off-road thing".
"It's too dangerous on the open road," he said.
He did know people, however, who went "quietly" on the roads and did not get bothered by police.
NZTA defines cycles fitted with petrol motors, low-powered scooters and cycles "designed primarily to be propelled by an engine not the muscular energy of the rider" as a moped and they needed to be licensed and registered.
"A power-assisted cycle fitted with electric auxiliary propulsion motors(s) that have a combined maximum power output not exceeding 300W are not motor vehicles and are treated as ordinary cycles."
Knackstedt said the "onus is on the person operating the vehicle to ensure it is properly licensed and registered before using it on the road".
The definition of a road in New Zealand is very broad and generally includes anywhere easily accessible by the public, including car parks and beaches.
Griffiths said police focused on how vehicles were being used and assessed it on a "case-by-case basis".
- Sunday Star Times
The lower drink-driving limits from December are:Related story: Drink-drive limits lowered