Cops have since launched a murder investigation after the “cowardly attack” in Battersea.
The 46-year-old victim was attacked on Saturday on Charlotte Despard Avenue around 4.30pm.
He suffered a head injury and died in hospital today.
The moped was recovered by police and is now undergoing a forensic examination.
A 16-year-old boy was arrested near the scene on suspicion of grievous bodily harm.
He was taken to a west London police station and has been bailed to a date in early June pending inquiries.
Det Chief Supt Mark Cranwell said: There is a busy Tesco store and other shops nearby in Battersea Park Road, and people will have seen these males in the area before, during and after the attempted theft of the moped and their subsequent cowardly attack.
“I want to reassure the community that there is an urgent and extremely thorough police investigation underway, and I am determined to find those responsible.
I also want to reassure them that any information provided will be treated in confidence and, even if people do not wish to contact police directly, they can provide information anonymously through the charity Crimestoppers.
“I am certain that several people – probably local to the area – will know what happened and who was responsible for this attack on the victim and on their own community. I need them to come forward and share information with me.”