Participant Spencer Bailey said the sight was "pretty spectacular".
"There's 800 or so riders, we're struggling to fit them all in. One side is full in Wynyard Quarter, they're wrapped all around it."
Ex-stuntman Craig Dunn, founder of Paw Justice, said New Zealanders were becoming less accepting of animal abuse.
"In the decade the charity has been operating, people [have] become more aware of animal abuse and more vocal about it."
Dunn said he was "stoked" with the turnout of riders, some who had come with their dogs.
"I was expecting a lot, but nearly 1000, it's just great... The engines will be speaking for the animals today."
The founder said the organisation was hoping to raise $100,000.
Dunn set up Paw Justice a decade ago following the death of his friend, Crocodile Hunter Steve Irwin.
