I cannot give you a definitive answer, but a couple informed cats here have said it was a Spector. Makes sense - that's more what it sounds like to me. Though I would also not be suprised if he used more than one bass during the course of the record (that was back when they still made 'records' by the way).
It was a stingray, he began using Spectors on the follow up record "the Uplift Mofo Party plan" and on "Mother's milk" The "Jungle man" video features footage of the entire "Freaky Styley" tour and all that Flea played were stingrays.
Oops...UMPP was actually the one I was thinking of having the Spector sound. I actually saw them on Freaky Styley tour and went mainly because Flea had been in Fear. Can't remember what he was playing, but it sure was bad ass! Yikes, that was over 20 years ago I bought Freaky Styley right away (after seeing them), but was very disappointed and sold it - dosn't have near the edge/attitude they did live...and it's not nearly as good as, say, the better pfunk records. 'course i was pretty into 'hardcore' then - i should revistit that one w/ fresh ears.