Sean Kingston -- Justin Bieber GAVE ME His Chrome Fisker Karma

It pays to be Justin Bieber's BFF ... 'cause Sean Kingston tells TMZ the Biebs GAVE HIM his old chrome-plated Fisker Karma simply because he got bored with it.

Kingston was leaving Boa Steakhouse in Hollywood this weekend when the valet drove up in the Karma ... which Justin initially got as an 18th birthday gift from his manager Scooter Braun.

So ... why did Bieber decide to re-gift his super-fast, super-expensive car?

Sean gave us the full explanation (check out the video) ... but Kingston should be careful -- 'cause Fisker Automotive recalled roughly 2,400 of the Karmas to fix a defective cooling fan unit that was the cause of a vehicle fire back in August.

The chrome car has a pretty infamous track record with police -- Justin was pulled over in the ride at least twice ... including one time for driving at breakneck speeds on L.A.'s 101 freeway.