Westport Volunteer Fire Brigade and St John attended the scene on State Highway 6 just south of Westport, between Wilsons Lead Road and the Lower Buller Gorge Road, about 4.15pm.
Deputy fire chief Trevor O'Dea said it appeared the motorcyclist was travelling along a straight piece of road towards Greymouth when a wheel from an approaching caravan came loose and "scored a direct hit" on the unlucky biker.
Traffic management was in place for over an hour while the first responders worked to make the injured man comfortable. He was airlifted to Christchurch Hospital with a broken leg and other injuries.
It was one of three incidents attended overnight in Buller.
The Westport brigade had earlier been called to a 2pm alarm activation at a commercial building in Palmerston Street. Instead of a fire they found a "very embarrassed" fire technician, who despite having isolated the system, had inadvertently triggered the alarm.
Today, the brigade had a virtual repeat of yesterday's 6am vegetation fire, dousing another fire in the same stand of bamboo at North Beach, also just after 6am.
Mr O'Dea said it seemed someone had relit yesterday's fire and while it was much smaller and only took 15 minutes to extinguish, it was nonetheless "very frustrating" for the volunteer brigade members.
- Meg Fulford
