Bradley Hooper, 16, from Farnham in Surrey, died after another biker hit him as he was picking up his bike at Down Farm in May 2014.
Coroner Grahame Short returned a verdict of accidental death but was critical of the way the track was run.
The inquest heard there was a "lack of" warning flags during the practice run at Headbourne Worthy, near Winchester.
Henry Siddiqui came over a jump at speed as Bradley was picking up his bike after a crash.
Mr Siddiqui, who was aged 15 at the time of the accident, thanked the Hooper family "for being really supportive and understanding".
"I knew deep down it wasn't my fault but I am glad it has been put on paper that it wasn't my fault," he said.
The yellow flag that would have warned other riders that Bradley was on the track was not waved in time.
Returning his verdict at Winchester Coroner's Court, Mr Short was critical of the way marshals were deployed and said he would be making recommendations to several organisations.
"It was unreasonable to put a 16-year-old [marshal] with so little previous experience in that position after having had less than 15 minutes briefing as to what is expected of a marshal," he said.
The Farnham Heath End School pupil had taken part in moto-cross since he was six years old.
On the day of his death, Bradley was one of 200 people taking part in a practice session at the course.
A statement from the Hooper family, read out by his uncle Kevin Duffell, said: "He was sadly taken from us at such a young age doing a sport he loved the most, moto-cross.
"He always had an infectious smile on his face and was hugely talented and lived life to the full.
"He was the sunshine in my life and now he is my angel."
The inquest heard the Crown Prosecution Service did not pursue any prosecutions due to insufficient evidence.
The death of a teenager at a moto-cross event in Hampshire has been ruled an accident by a coroner.