In what film were there motorbikes riding out of graves or sum1 buried on 1?

That sounds like this film:

Psychomania (1973)

aka The Death Wheelers

starring Nicky Henson, Ann Michelle, Roy Holder, Beryl Reid, George Sanders

IMDb synopsis:

A gang of young people calling themselves the Living Dead. terrorize the population from their small town. After an agreement with the Devil that, if they kill themselves firmly believing in him, they will survive and gain eternal life. Following their leader, they commit suicide, but things don't turn out as expected.

This definitely is your movie, as you'll see form this review:

With scenes such as a a biker jumping to his death after telling a cop "I'll be right down!", A BIKER BLASTING OUT OF HIS GRAVE ON HIS MOTORCYCLE {my caps}, a biker coming back from the dead in the morgue and calmly walking out like he just woke up from a nap, etc., all accompanied by some seriously sweet rock music, this is about as cool as it gets.

Here are some film clips:

http://www.youtube.com/watch?v=b0SEdTlJ0Wk

http://www.youtube.com/watch?v=Q1-tDvENdkE

So, my memory didn't play tricks on me! I have this one in my videotape collection, an actual boxed video for a change. Long, long ago, I bought it for maybe $2 at Wal-Mart.