Jim Morrison liked to brag about his fast-lane lifestyle. “I’m gonna get my kicks before the whole s – – thouse goes up in flames,” he was fond of saying.

Turns out his body was the

s – – thouse. And like an arsonist in leather pants, he burned it to the last cinder, a spectacle that nobody close to him enjoyed watching.

“It was very upsetting to sit by and watch him deteriorate,” Doors keyboardist Ray Manzarek tells The Post while reminiscing about the Lizard King’s most debauched moments. The dark side of Morrison’s fame and charisma is revisited in the new documentary “When You’re Strange: A Film About The Doors,” out on DVD Tuesday, also featuring guitarist Robby Krieger and drummer John Densmore.

Loaded with previously unreleased concert footage, family films and a candid interview with Morrison’s Navy-officer father, director Tom DiCillo’s film chronicles the group’s dizzying success, drug-

induced hardships, chaotic concerts and six classic albums.

Here are some of the film’s maniacal Morrison moments, along with Manzarek’s recollections:

 West Hollywood, 1966: Morrison drops so much acid at the Whiskey A-Go-Go that he collapses onstage.

“I took LSD, too — it helped open the doors to perception,” Manzarek says. “LSD could show you heaven, but it could also show you hell. A bad acid trip could take away all the swirling energy that makes you live. We really didn’t take it before shows, though. Well, maybe Jim did. Normally, John, Robby and I would smoke a joint and drink some beers before [going] onstage.”

 Los Angeles, 1968: The band’s sessions for “The Soft Parade” are constantly upended by Morrison’s erratic behavior.

“I think aggravating is the perfect word,” he says. “We would sit there and hope the good Jim Morrison would show up. Sometimes he did and the studio sessions were fantastic. But then ‘Jimbo’ would appear, completely drunk and unable to string together a sentence without slurring. It was the height of his alcoholism.

“The guys in the band would try and help him, but it didn’t help. He was an Irish poet and what do they do? Drink and drink and drink.”

 Miami, 1969: Morrison whips out Jim Jr. at the Dinner Key Auditorium. Cops promptly arrest him for indecent exposure.

“Sure I was scared — the crowd was in a frenzy,” Manzarek says. “I thought they were going to grab Jim and tear him to pieces. I actually kept on playing the keyboard, though. It was my job to keep the music going. [Laughs] I mean they weren’t going to attack me — I’m only the keyboard player. The lead singer is the one in danger. By the way: Do people even go wild at rock concerts anymore?”

 Paris, 1971: Morrison dies in the bathtub of his apartment, apparently from a heroin overdose.

“When I found out, it completely broke my heart,” he says. “You could see my reaction in the film. The group died spiritually, creatively and even financially. It’s really sad because it seemed Jim [had] resurrected his life. He went out to Paris for a break after ‘L.A. Woman,’ and we planned to record a new album with him shortly after. Unfortunately, he never came back.”