shifting

This 1982 XS400 Maxim only has four gears. 1 down, neutral, 2 up, 3, 4, ... No fifth. Too bad, it could use a fifth gear for speeds over 50. At first we just shrugged and accepted this, but now that I read up this definitely seems wrong. The Maxim is a five-speed, yes? (unlike other XS400s...