Mr Pilkington was walking on a pathway when he heard the motorbike coming from behind but he couldn't get out of the way and the motorbike hit him.
As a result Mr Pilkington suffered extensive injuries to his right hand, cuts to his legs, facial bruising and needed hospital treatment, Sergeant Lawrence said.
Police said Mr Pilkington's finger was partially severed.
Hart was later found by police and told them he had taken the motorbike to go joy riding.
Judge Stephen Harrop said the charges against Hart were serious, carrying maximum terms of imprisonment ranging from five to 10 years. The judge said Hart was a young man with no previous convictions. He was not prepared to sentence Hart until he had more information, including a victim impact report.