500 cc sounds about right for a small bike. My (not Yamaha) 125s take 450cc and my 250s take 900.
500cc is in the correct range IMO.
My bikes use straight EP80, but I've had other two strokes that run on engine oil or ATF.Yamaha yz80 gear oil level and type????? 1998 yz 80?
Have you pulled the fill plug to see if it has a dipstick?
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