Eldest son Luke Mulder, who was due to be married next week, flew back from the United Kingdom to help coordinate the search for his father.

"Siemon Mulder, our dad, was a true gentleman," he told Brisbane Times.

"He was a kind and gentle man who loved his motorcycles and always put his family first."

He said he would hold on to the memories of going on motorcycle adventures and learning to ride with his father.

"All of the family has been very touched by all the people who have helped with the search and the people around the world who have supported us," he said.

On a fundraising page set up to support Mr Mulder's wife, Wendy, friend Karen Rigney thanked the hundreds of people who helped in the search.

"This morning a biker had a small accident on an outback road heading towards Maleny. As he went to pick up his bike, he spotted another bike matching the description of Siemon's Triumph further down the embankment and immediately contacted the police," she wrote.

"A body was spotted and airlifted from further down the embankment which police and rescue have now confirmed is Siemon.

"We just want to say how incredibly grateful the Mulder family is for all the support from the police and the greater community, this exhaustive search was on a massive scale and now there will be an autopsy to determine cause of death and a funeral to prepare for."

Police believe Mr Mulder crashed on a left-hand bend on Maleny Stanley River Road at Booroobin.

"Formal identification has to yet to be conducted however it is believed to be missing Sandgate man Siemon Mulder," a police spokesman said.

In an interview with Seven News on Wednesday, son Paul Mulder said his elder brother had made the trip out early before his wedding to help coordinate the search for his father.

A report will be prepared for the coroner.