If this helps, I had the same issue on my 1983 XT250 the CA Model. Parts if available are scary expensive. I had a bad rocker and camshaft...took a chance and found a cam from a 1982 TT250 and fit & worked just fine.
Just signed up...Member in a few other forums as well. current project 1983 Yamaha XT250. Just purchased a 1981 XT250 Parts bike to complete the bike. Wiring harness is complete but giving me drama. Hoping to get the answers here or sell it all off kinda love hate thing I guess.