Ian Martin, 61, attacked the victims at various locations in the Ely area between February 1976 and April 1981.
He would threaten them and said they would be put in care if they told anyone, as well as giving them money to buy sweets afterwards.
On one occasion he asked one of the victims if she wanted to have a go on his motorbike, before taking her to a secluded spot and raping her.
On another, Martin raped them in bunk beds.
On 8 June, at Cambridge Crown Court, Martin, of Padnal, Littleport, was jailed for five years, having been found guilty of two counts of rape after a re-trial.
He was found not guilty of another count of rape and no verdict was given on two further counts of rape, all involving the same two girls.
Martin had already been found guilty of one count of rape at his initial trial in June 2021.
DC Jen Rouse said: “Martin carried out his awful crimes over a five-year period which must have been a truly terrible time for his victims.
“I am delighted he has now faced justice and I would like to pay tribute to the victims in coming forward and having the courage to support us with a prosecution.
“Martin’s abuse has had a huge impact on their lives and I hope they can now find some closure from this traumatic period for them.”
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