There was indeed a motorcycle gang in the pilot for the Flash TV series. They were the bad guys for the pilot. They killed the Flash's brother, played by Tim Thomerson. The time frame is correct for the series.
http://www.imdb.com/name/nm0859772/If you can, track down the first episode with Mark Hamill as the Trickster. It's a fantastic episode and Hamill is clearly having a ball. There was a second episode as well, but it wasn't nearly as good. He brainwashes the Flash to be evil and the Flash's actor is horrible at acting evil.