Bow Wow to Mike Vick -- I Can't Help You Sell Hair Brushes to Black People

Bad news for Mike Vick ... his friend Bow Wow won't be helping him sell special hair brushes to black people ... after a high-profile business deal fell through, TMZ Sports has learned.

It was just last year that Vick announced plans to release a line of "wave brushes" called WaveMasterz -- brushes that come complete with a mirror on the back so users can ensure they look fresh at all times.

Bow Wow was reportedly involved in the project ... and at one point, his name was on the top of the WaveMasterz website ... but now, the rapper tells us the plans have changed.

"It was supposed to go down," Bow Wow said ... "but all deals don't go down the way you want them to."

Bow Wow says he didn't want to spread himself too thin -- since he's already involved in a clothing line, a vodka line and hosting "106 and Park" on BET.

BW -- who was at Last Kings clothing store in L.A. -- said there are no hard feelings between him and the QB ... explaining, "Michael Vick is still a close friend of mine, I wish him the best."