"I've only smacked my head once previous to this latest spill, but it made me re-evaluate things. I believe concussion is taken too lightly in this sport, anyway. But, with so many injuries, I was just sick and tired of the direction my career was taking.
"I told my Carlton Dry Honda team that I can't deliver the championships I promised them while I'm injured and, after this last fall, I realised I needed to take time off to fully recover.
"I left school when I was 16 and have been racing a long time now. It was a very hard decision to make and I have thought long and hard about it this week. I think it is the right decision.
"I want to do something completely different with my life now, with my wife and our two boys," he said.
"While I am retiring from full-time competition, I will still ride and race at selected events. One thing I have never done, which I'd like to try, is racing the annual Tarawera 100 [cross-country endurance race, near Kawerau]. Perhaps I'll race that.
"Although I am retiring from fulltime competition, I am not walking away from the sport. I love motocross and understand and accept that we can get injured. I am only 28 years old and I believe I have a lot I can give the sport."