You might rethink it needing new crank seals on your FA50 .
The OEM seals are premium . Mine are original from 1984 and are fine .
I'd get it running before you start tearing it down . You might be pleasantly surprised .
You'll need an OEM air box and connector tube for it to perform as intended .
Mine does 28 - 30 MPH all day long , completely stock .
I've found that getting to know and use a parts fiche is a great help and source .
There weren't a lot of changes made to the FA50 over the years . Cosmetics for the most part .(edited)