Police say alcohol was a factor in the crash, as they have information Mr Whitney was drinking at a local nightclub prior to the incident.
Mr Whitney was not wearing a helmet, and suffered serious head injuries.
This is the second crash this year on Rarotonga's roads which have involved a New Zealander and the cause of each crash was alcohol related said Inspector Tere Patia, for the Cook Islands Police.
In June Able Seaman Combat Specialist William Paratini Delamere, 22, was killed in a drink-driving accident in Avarua. The crewman of the HMNZS Otago had a scooter accident after a night of partying while on shore leave.
The Cook Islands News also reported that Inspector Patia added: "Not all tourists are causing havoc on the roads.
"It's only the very few that's causing the problem. The same message about the dangers of speed and alcohol when driving get repeated all over the world, but repeatedly people ignore it.
"When a person decides to drive after consuming alcohol, or speed or drive carelessly without due regard for their safety and the safety of others, it is already too late."