To sort of get things going for this part I am going to use quotes from John and Yoko straight from interviews. I think these make a good start for this:
Yoko: By then, it was getting very obvious that the world didn't want us to really work together. So it was 1973, I just felt like saying to John, "Well, look, why don't you just go to LA and have fun," you know. Leave me alone, you know. And I just wanted to think straight 'cause I couldn't think straight anymore.
John: She literally said, "Get out." You know, and I said, "ok, ok, I'm going." You know, I'd been married before Yoko and I immediately married Yoko. So I've never been a bachelor since I was 20 or something. So I thought, "Whoo-hoo, ha ha!"
This was to become John Lennon's 18 month lost weekend. This is where John totally lost control and indulged himself into every little part favor there was. He was living with some of the rowdiest people in Rock n Roll. The Party mates consisted of Ringo Starr, Keith Moon, Harry Nilsson, Mickey Dolenz, Elton John, David Bowie, Jesse Ed Davis, Klauss Voorman, etc.
Harry, John, Ringo and Keith all living in the same house as a matter of fact. You can imagine what style of life he was living during this part. He was frequenting some of his favorite places in LA. John and Harry went to go see the somethers Brothers one night when they had to bodily remove John from the club. It seems that John went into the bathroom and there was a clean kotex so he wet it, smacked it on his forehead so it stuck and went back out to the club to show it off to his friends.
And then they were being so obnoxious during the show they were asked to leave and Its told that John got a little out of control and they had to through him out by force. Here is his statement from the Imagine movie:
John: We had a lot of fun. There was Keith Moon, Harry, me, Ringo, all living together in the same house. And we had some moments, folks. But it got a little near the knuckle. I hit the bottle like I was 18 and 19. And I was acting like I was still at college. It was the first night I drank Brandy Alexanders, which is brandy and milk. And I was with Harry Nilsson, who didn't quite get as much coverage as me. They just sort of said, "OK, you better leave, Mr. Lennon." And then took me out, so it was a mistake. But well, I'm human, you know? I was drunk in Liverpool and smashed phone boxes. Huh? But It didn't get into papers then. Nobody was looking for me. And I needed somebody to love me. And there was nobody there to support me. And I-I fell apart.
He had begged Yoko to take him back at this point but she said he was not ready, so he said "Ok, back to the bottle!" and continued his get together with the good ole' boys until Yoko ran into him at an Elton John concert.
But this period was not a complete waste of John's time. He worked with David Bowie on his album Young American. He also worked with Elton John on Whatever gets you through the night. Which John and Elton had a bet going. Elton believed that this song would reach #1 in the charts and John disagreed. The bet was , if it did, John Lennon would have to perform with Elton on stage for this song and a few others. John made good on his bet. And I think it was to be John's last performance.
The song list consisted of:
It was here at this show that Yoko appeared. And this is where they started to rekindle their relationship.
But it is also told through "Paul McCartney: Many Years from now." That Yoko went to England and spoke to Paul about this. Said she needed John back. And Paul offered to go and talk to him for her. When Paul arrived he found John in the studio and approached him. Asked John if he really wanted to go back to Yoko and John said yes. So Paul said: "Yoko wants to be courted, she wants to be taken out on dates. She doesn't just want to go back to the way things were". And from there John started to make his moves.
This story has been told in many different ways. There is Yoko Ono's side, May Pang's, Elliot Mintz's and even Paul McCartney's. But the only real person who could have ever told what it was "really" like during the lost weekend was John Lennon.