Black Chyna's teenage ex-boyfriend is claiming that her private parts are "loose."

Last night, Black Chyna's ex-boyfriend YBN Jay took to social media, to disrespect his ex - and claim that Chyna's "p***y is loose.". 

YBN Jay went on a rant, after fans pointed out that Chyna has moved on from him, and is dating another rapper.

Chyna is now dating Kid Buu - a rapper who got famous by claiming that he's a clone. Here are pics of Chyna and her new bae two together:

Chyna_Kidbuu

Well YBN Jay is feeling a way about Chyna moving on - and decided to disrespect her in the worst way. Jay told his fans that Chyna was like an old car, and that she has "too much mileage." He also said that the Instagram star needed an "oil change."

Then YBN Jay claims that her private parts were "loose."

Here is a video of the rant:

Blac Chyna's suspicions about YBN Almighty Jay cheating on her are inaccurate ... at least when it comes to his ex-GF, turned baby mama.

As you probably know ... BC dumped her 19-year-old piece earlier this summer, because she was fed up with YBN sliding into different chicks' DMs and possibly having a side piece.

His announcement over the weekend that he now has a new baby boy -- SirLucius Edward Scott-Bradley -- might seem to confirm her fears, but we're told the baby making went down before Chyna was in the picture.