Harley Davidson refused to provide free bikes for the film because they felt it would be bad for their image.
In the scene where Fonda, tripped on acid, speaks to a statue in the cemetary he calls it "mother". This is because Hopper instructed him to talk to the statue as if it were his mother. Fonda's mother committed suicide when he was 10 and in the speech he talks about how he loves and hates her. Fonda had never confronted his feelings about his mother before that.
Dennis Hopper was in a bad way during the filming of Easy Rider, induced into a paranoiac state from the drugs he was taking.
Fonda's chopper was so difficult to ride and sit on that Jack Nicholson, riding in back for one of the scenes, squeezed his legs so hard against Fonda that he broke one of his ribs.
Fonda and Hopper did not have a full script when they began shooting the movie and much of the filming was improvised with hippies from communes across America and nearby pedestrians to hold the cameras.
Easy Rider was one of the earliest films to use music that was previously released. Most other films of the time had their own scores.
Fonda rode about in the motorcycle in the film for a week in his Captain America jacket with the intent to "break it in". During that time he was pulled over several times for his... highly patriotic appearance.
Fonda was a very experienced rider and for this reason his motorcycle is much more radically inclined and stretched compared to Hopper's.
Peter Fonda, Jack Nicholson and Dennis Hopper were smoking actual marijuana in the movie, though they did not take lsd.
Four police bikes were reportedly made for the film, but three were stolen before the movie was completed and the fourth was burned on set.