As a CFI, if I give training for a private applicant in a J-3, I'm
legal, but to give training for a sport pilot applicant I must get an
endorsement in my log book for that airplane and have 5 hrs PIC???


http://www.aopa.org/sportpilot/cfi_certification.pdf

Appropriate Category and Class Ratings in
LSA (5 hours PIC make and model within a "set" of
aircraft additional Category and Class Privileges Endorsed
in Logbook)