Sylvester Stallone Again Hits Out at 'Rocky' Producer Over Drago Spin-Off

Sylvester Stallone isn't pulling any punches over his dissatisfaction with where the 'Rocky' franchise is heading -- once again publicly lashing out at one of the OG producers.

Sly went on the attack for a second time this weekend, posting a very scathing message aimed at Irwin Winkler ... who helped get 'Rocky' off the ground way back in the day, and who apparently has an ownership stake in the IP -- while SS has none himself.

That's where Sylvester's beef lies, and he made it clear in yet another critique on Instagram ... throwing up art renderings that depict Irwin and others as animals and evil villains, who are stabbing Sly in the back, etc.

Sylvester writes, "After IRWIN WINKLER And FAMILY SUCK ROCKY DRY ! Presumed to be the most hated , untalented , decrepited , Producer in Hollywood and his cowardly children have found their next meal… Drago , RETURN MY RIGHTS BLOODSUCKERS!"

He's talking about the fact that Dolph Lundgren is reported to be starring in a spin-off film that'll see him reprise his character from 'Rocky IV' -- something Sylvester says he wasn't made aware of, and which he strongly disapproves of ... saying he never meant these precious characters of his to be milked to this degree in future projects.

Sylvester says he sees this as nothing but a greedy money-grab, and even calls out his old costar by name -- asking why he didn't reach out to talk about this before the word was out.

BTW, a couple weeks ago ... Sylvester was also venting frustrations about not owning any of 'Rocky' for himself ... and he pleaded with Irwin to do the right thing and hand over some of the rights, which he feels -- at least in part -- belong to him since he's the creator of 'Rocky.'

Sylvester has been speaking out about this more and more lately -- and it's starting to turn ugly. Some fans side with Sly ... while others are calling him out for acting unprofessionally.

As for Dolph, he's addressed Sly's concerns, writing ... "Just to set the record straight regarding a possible Drago spinoff. There’s no approved script, no deals in place, no director and I was personally under the impression that my friend Sly Stallone was involved as a producer or even as an actor. There was a press leak last week which was unfortunate. In touch with Mr Balboa - just so all the fans can relax…There ya go."