The Hellcats
The Hellcats, also known as Biker Babes, is a 1967 outlaw biker film starring Ross Hagen and directed by Robert F. Slatzer. It was featured on the television series Mystery Science Theater 3000.
Following this, Chapmans brother Monte, a sergeant in the United States Army, returns from active duty only to learn of his brothers death. Vowing revenge against Adrian, Monte joins forces with Chapmans fiancee Linda who poses as his girlfriend and together they pretend to be bikers and join the Hellcats, during which time Monte becomes romantically involved with Sheila, the girlfriend of the Hellcats former leader.
Source: Wikipedia