Clymer M447-2 says middle of sight window (pg.66)
Recommended oil Table 3 (pg.102) SAE 10/30 or 10/40 (I'm not touching this one with a ten foot pole!)
Capacity clutch/tranny Table 6 (pg.103) KX 500 1983-on 800 cc's or 27.1 fl.oz.
also found in Quick Reference Data (front of book) pgs. IX & XI
Tuck\o/