A Honda Fireblade motorbike stolen from a locked garage on Sovereign Parade just after midnight on Saturday was found on fire in the Valley Gardens at 5am.
A Cona Hoale racing pedal cycle was also taken from the garage, but has not been traced.
Police investigation the theft say three men were seen pushing a motorbike along Cornwall Road towards Harlow Moor Drive at the time.
One of them was around 6ft tall and slim, while another was around 5ft 6in tall. They were wearing hooded tops and hats.
PC Simon Pape, of Harrogate Safer Neighbourhood Team, said: “If you have any information about the men responsible for this theft or saw the motorcycle being set on fire I urge you to contact the police or Crimestoppers straight away.
“I would also like to speak to anyone who knows where the racing bike is now.”
Anyone who can help with the inquiry is asked to contact Harrogate police on 101, press option two and ask for Simon Pape. Alternatively, call Crimestoppers anonymously on 0800 555 111 quoting reference number 12120118194.