dunno, i'm not hearing clean when i listen to most of the big names from the 70s, especially not their earlier material. dunno, maybe we just interpret things differently.
this track's been posted a few times (and covered by Soundgarden on their first ep) but if this doesn't sound like dirty funk to you then i don't know what else to say.
YouTube - ‪Ohio Players- Fopp (vinyl)‬‎