CrushWashers
From LinerWiki
Replacement Oil Drain Crush Washers
The crush washers can be obtained at your nearest Yamaha dealer, or similar washers can be obtained at Advanced Auto. The size is 1/2 (or M14) called oversize, crush washers.
Oil-tite part #65310
There come in a 3 pack.
Reference: http://forums.delphiforums.com/starroadliner/messages?msg=12637.15