Queensland's roads claimed two more lives this weekend, with the deaths of two motorcyclists in separate crashes.

Police are yet to piece together the circumstances involving a 26-year-old male rider who came off his bike on Johnson Road at Kia Ora, near Gympie, just before 4pm yesterday.

He was airlifted to the Royal Brisbane Hospital but died overnight.

Meanwhile, a 58-year-old man was killed instantly when he was thrown from his motorcycle at Ashgrove, in Brisbane's north west.

It is believed the man had been changing lanes on Waterworks Road near the intersection of Ashgrove Avenue when he collided with another vehicle merging into the same lane.

Police said the rider lost control of the bike and was thrown onto the road after hitting a power pole.

He died at the scene.

Officers from the Forensic Crash Unit are investigating both crashes.

Anyone with information is asked to contact crime Stoppers on 1800 333 000.