A Horbling teenager died hours after walking away from a crash in which the trial bike he was riding hit a car on a road in the village.
Scott Blair was just 16 when he lost control of the 200cc machine he was delivering to his father, Allan, who had bought it.
At his inquest at Stamford Magistrates Court on Thursday, South Lincolnshire Coroner Prof Robert Forrest said the collision with a red Fiat took place in Sandygate Lane, Horbling, close to his home in Stow Lane on Monday July 23, at about 4.30pm.
Prof Forrest said Scott was able to ride away from the scene but later became ill, and when paramedics arrived Scott was struggling to breathe.
He became calmer and was taken to Boston Pilgrim Hospital, where he suffered a heart attack and died.
Consultant pathologist Dr Michael Harris said Scott had received fatal lacerations to his liver that led to an abdominal haemorrhage.
He said the bleed would have built up over a period of time which is why it was not evident at the time of the crash.
Driver of the Fiat, Belinda Hay, said she saw Scott coming towards her from about 100 yards.
She said: “When he lost control and hit the floor his helmet came off straight away. I was braking hard but could not stop before the impact.
“When I opened the door he was under the car, it’s hard to say how long it was before he got up.”
Accident investigator PC Mark Brown, said: “The motorcycle was for off-road use only and it was not road legal. The 200cc engine was too powerful for someone with little experience.”
Scott’s sister, Linda, said she could confirm his grandfather had told him not to ride the motorbike.
Recording a verdict of accidental death, Prof Forrest said it was a tragic accident. He said: “He was told by his grandfather not to ride the motorbike but he did.”