FMSA California is a good example of a bike brand almost too obscure to document. Only a single example MTB exists with a single picture.
It's likely FMSA California was a sub-brand of Fairly Bikes, a large Taipei based manufacturer founded in 1977 who also supplied the early Diamond Back MTBs. If so, then “FMSA” may be an abbreviation of Formosa, a synonym for Taiwan. Evidence for the Fairly connection includes the FMSA MTB being identical to the Diamond Back Trail Streak.
FMSA did produce a few BMX bikes from 1982-87. Ebay usually has a number of FMSA head badges for sale, perhaps indicating the badges are worth more than the underlying bicycle.
Identical to the 1984 Diamond Back Trail Streak, except that the FMSA California has some earlier components.
Pump pegs, TIG welded, rear SunTour GT RD-1200 (1981-3 with this style), front Shimano FD-M700 (82-86), Tracer cranks (1983 in this style) 1), and SunTour LD-2800 shifters (1983-85).