The rider, Belgian Stig Broeckx, 25, was taken to the hospital.
He was sitting upright after hitting the ground.
It was not immediately clear what his injuries were.
Here's the moment the motorcycle driver hit Broeckx:
Broeckx rides for the Lotto-Soudal team and was racing in the Kurne-Brussels-Kurne semi-classic, one of the opening races of the famed Belgian cobbled-classic season.
.@StigBroeckx is at the hospital for further examinations after his crash at @KuurneBxlKuurne. More info later.
- Lotto Soudal (@Lotto_Soudal) February 28, 2016
Last year a motorist struck a cyclist:
Poor @jessesergent knocked down by car at #RVV. pic.twitter.com/TpRMxb6Dnm
- daniel mcmahon (@cyclingreporter) April 5, 2015
More to come.