Hammond pulled back off the road and went to help McNaught who was trapped under his bike.
Passing motorists called emergency services and helped comfort McNaught.
"Ambulance and police arrived at the scene a short time later, but the victim died at the scene as a result of his injuries."
On Friday Hammond appeared before Judge Bruce Northwood in the Ohakune District Court charged with careless driving causing death.
Hammond pleaded guilty to the charge, which has a maximum penalty of three months' imprisonment, $4500 fine and a minimum disqualification of six months.
Judge Northwood remanded Hammond for sentencing on October 21, and to see whether a restorative justice conference could be held with the victim's family.
McNaught was a valued member of Matamata's Walton Boxing Club and just prior to the crash had left the New Zealand Boxing Championships in Whanganui.
Walton boxing coach Raymond Richards described the 50-year-old as having a "heart of gold" and said his death was devastating.
"He was a wonderful man, a tremendous asset to the club and devoted to the boxers.
"It was just so devastating and such a loss to his large family, the club and the wider community."