He was drinking and speeding in the lead up to the crash and was not wearing a helmet, police said.
"Sadly, speed and alcohol are factors that we believe have contributed to this crash, and we have confirmed a crash helmet was not being worn by the rider,'' Senior Sergeant Ian Kerrisk said.
Mr Mackenzie was found by a family member about 6am this morning near the intersection of Partridge and Shortcut Rds.
"That person commenced CPR, but he was confirmed dead at the scene by attending medical staff,'' Snr Sgt Kerrisk said.
The police serious crash unit have finished the examination of the scene and Shortcut Road reopened around 2pm this afternoon.
"We have spoken to the family and with a number of persons living near the crash site. That, along with the scene examination means we now have a much clearer picture of what occurred,'' Snr Sgt Kerrisk said.
"Nearby residents had heard a motorcycle travelling around the area about 4am this morning, with the noise stopping suddenly shortly after.
"We believe that Mr Mackenzie collided with a fence at around 4.15am this morning and has died instantly.''
The death was avoidable and a "tragic loss for the family'', he said.
"Alcohol is the second biggest contributing factor to road crashes in New Zealand," he said.
"Even small amounts of alcohol begin to impair your ability to drive as it slows your reaction times and affects your senses and judgement.''=
The motorcycle involved in the crash was an off road dirt bike.
No other vehicles were involved in the accident.
The death is the 12th on New Zealand roads this holiday period.
Superintendent Steve Greally, national road policing manager, made a statement this afternoon saying police were extremely disappointed in the road toll.
"We are just halfway through the holiday period and the toll is already equal with last year,'' Supt Greally said.
"That means twelve families who we have had to break devastating news to.
"They now have to spend their holidays saying goodbye to a loved one.
"While these crashes are all under investigation and it is too early to speculate on causes, I can say with some confidence that they were all avoidable.''
Of significance, a third of the fatalities so far had been motorcyclists, he said.
"Every time you approach a car - or motorbike - with keys in your hands, you need to be aware that your decisions affect more than just yourself,'' Supt Greally said.
"You have to think about your passengers, other road users, your family and friends and the loved ones of other road users.
"Think about how your family and friends would feel dealing with the loss of your life.
"How you would feel if you were responsible for the death or serious injury of one of your passengers? Or any other road user?
"I know it's tempting to take risks and that we think `it won't happen to us'. But it can, and it does.''
The risk was not worth it, he said.
"I can't say it enough - watch your speed, your following distances and wear your seatbelts.
"Adjust your driving to the conditions, whether it's weather, the state of the road or the driving of other motorists.
"Above all, if you see any driving that causes you concern, don't hesitate to call *555.
"We will do something about it.''
