Andrea Lehane, 34, was thrown more than six metres when 18-year-old Caleb Jakobsson hit her with his home-made mini motorcycle, as she walked across a zebra crossing outside the Carrum Downs Shopping Centre on September 23, 2015.

Jakobsson, now 20, fled the scene with his friends, leaving the mother of two on the road with severe brain injuries.

She died in hospital days later. He later admitted his crimes to police.

County Court Judge Jane Campton sentenced Jakobsson on Tuesday to seven years in an adult jail for culpable driving causing death and failing to stop immediately after an accident.

She imposed a non-parole period of four years and disqualified him from applying for a licence for four years.

"As a result of your negligent actions a young woman, who should have had the rest of her life to look forward to, has met a traumatic death," Judge Campton said.

"Her husband and two young children have been deprived of both a wife and a mother, and no doubt will suffer grief for many years to come."

Jakobsson's decision to leave the scene was "morally reprehensible", and he should have known she had either been seriously injured or killed in the crash, she said.

Judge Campton said this was a serious example of culpable driving given Jakobsson was travelling at more than twice the 10km/h limit over a pedestrian crossing on a motorbike he knew had a compromised brake system.

The court heard the bike - which Jakobsson has said is a Thumpstar model - did not have front brakes and had to be stalled to turn the engine off.

Jakobsson's lawyer previously argued he should be imprisoned in a youth justice centre, where the maximum sentence is three years.

The maximum sentence for culpable driving causing death is 20 years' imprisonment and for failing to stop is 10 years' jail.

The crime was frequently committed by young men, she said, which meant it was important that the sentence be used to deter others.

While he was a young offender, his prospects for rehabilitation were "guarded", given he was immature and had committed offences on bail, including taking the drug ice.

In his victim impact statement, Mr Lehane said: "Overnight this cowardly and easily avoidable crime left me a single parent to very young, innocent children.

"None of this is something I could ever foresee or prepare for in any way."

"In an instant this crime took Andy away for eternity.

"Andy's natural expectation to live a reasonably long life was carelessly tossed away for the sake of cheap, reckless thrills."