That's a nice bike! I have a similar one; a "triathalon" model sold by KHS in the 80s. Similar paint scheme too, except green where yours is red. It makes you wonder if they were built in the same factory. It was perfect for my son when he was 5' tall. Check on that stem installation. Unless it's a Nitto Technomic or something similar, make sure that there is enough of the stem in the steerer.