He joined Rotorua's Lachlan Stevens-McNab, 9, as an age-group world champion on Thursday, after Lachlan won the 9-year-old boys section during the morning session.
This is Mohi's second age-group world title.
Other Rotorua BMX Club riders also performed well during the second session on Thursday, with Jeanette Davies and Daniel Bowers-Wilson (Christchurch) finishing third in their age-group finals.
The age-group competitions finished up on Thursday evening after two days of quality racing.
New Zealand now have 12 world titles at this year's world championships, ahead of the United States and Australia who have six each.
Rotorua BMX Club vice-president Craig Elliott said the club was proud of all its riders who had taken part during the event. "On behalf of Grant and the rest of the committee congrats to all of our club riders," he said.
"History has repeated with Lachie and Dave being champions of the world together."
Rotorua Mayor Kevin Winters also congratulated the Rotorua team via their Facebook page.
"Huge congratulations to our riders on their achievements and for making Rotorua and New Zealand proud."
The track at the Vector Arena was modified yesterday to prepare for the elite riders who will be racing this weekend.
Kawerau's Sarah Walker will lead the way for New Zealand in the women's elite competition, despite the pain of an arm injury.
The finals for the elite riders will be held tomorrow from 3pm.
