A 24-YEAR-OLD trail bike rider has died after he crashed into a tree southwest of Sydney.

The man was riding with friends at a rural property at Bargo when he got separated from the other riders yesterday afternoon.

Police say it's believed he was doing a u-turn when he crashed into a tree, causing the motorcycle to fall on top of him.

His friends later found him and tried to resuscitate him but he died at the scene.