"Some rust" more accurate would be some bike. -- https://www.ebay.com/itm/1973-Rd-350/223945753263?_trkparms=aid%3D777001%26algo%3DDISCO.FEED%26ao%3D1%26asc%3D225074%26meid%3D4cf5c0c7d123450b8ee443c9b65f62ab%26pid%3D100651%26rk%3D1%26rkt%3D1%26mehot%3Dnone%26itm%3D223945753263%26pmt%3D0%26noa%3D1%26pg%3D2380057%26algv%3DPersonalizedTopicsRefactor&_trksid=p2380057.c100651.m4497&_trkparms=pageci%3A928e1d4a-676b-11ea-a1fe-e6378def4d3c%7Cparentrq%3Ae2c07ca11700aaf84addb82bffd5df56%7Ciid%3A3
350 not bad the 400 (1982 on tag) doesn't look like real deep but oddly looks like was painted with rust. -- https://www.ebay.com/itm/1976-Yamaha-RD400/184212394806?hash=item2ae3ea1336:g:2y8AAOSwPStebqmU --- https://www.ebay.com/itm/1973-Yamaha-RD-350/184212396480?hash=item2ae3ea19c0:g:LzMAAOSwoPZebqZo
thats from leaving it under a non breathing cover in a damp area for along time. seen that a few times.