Joshua Williams, 18, was found guilty at the Old Bailey, with the prosecution accusing his family of changing their story after initially confessing.
The court heard how Williams lashed out with a blade as popular young student Alan Cartwright was riding along Caledonian Road, north London, with his friends in February.
He has been jailed for life with a minimum of 21 years for what the judge described as a "gratuitous and senseless piece of violence".
In March, Williams went to Islington police station with his parents to hand himself in, the prosecution said.
He arrived with his mother in tears clutching a Bible.
When asked why they were there, his mother is accused of telling an officer it was about the incident in Caledonian Road, saying: "Yes, he's involved, he did it."
And as he was taken into custody, Williams, who lived off Holloway Road, north London, was allegedly heard by another officer to say: "It's the right thing to do, isn't it?".
But in his defence, Williams claimed he was at a youth club that night and he only went to the police station to tell them that he was not involved in the incident.
Once his story had changed it's claimed his mother also changed her version of events.
But when called to give evidence on the issue from the witness box she, his father and brother, refused to swear on the Bible.
Prosecutor Mr Rees told jurors that his alibi was in tatters and the evidence from his family was "disappointing" because they had "decided to abandon their principles to support him in his lies to the court".
In a statement read to the court, Alan's mother Michelle Watson, 40, told how news of his death came as an "unbelievable shock".
She said: "Life without Al is killing me as his mum. It's also had a devastating effect on his family. He loved his dad Al senior. Al has not been able to go back to work since this happened.
"He says he cannot see a future without him. He was our loving boy - our only son."
His father Alan Cartwright senior, 44, said: "It will make people think twice about carrying a knife."
The family of killer Williams refused to speak to journalists.
