The drain plug washer is a service item and should be replaced at a regular interval
Made from soft aluminium its job is to compress and provide a seal between the drain plug flange and the crankcase.
If this part is not replaced you risk stripping out the crankcase thread when overtightening the drain plug in an effort to stop oil leaking.
Dont risk it, just replace it.
Suits ATC70 73-85, ATC90 70-78, ATC110 79-85, ATC125M 84-87, ATC185S '83, ATC200 82-83, ATC200E 82-83, ATC200M 84-85, ATC200S 84-86, ATC200X 86-87, ATC250ES 85-87, ATC250R 81-84, ATC250SX 85-87
Also suits MR50 74-75, QA50 70-75, Z50A 68-78, Z50R 79-99, C70 72-83, C70M 70-71, CL70 69-73, CT70 69-94, SL70 71-73, XL70 74-76, XL75 77-79, XR70R 97-03, XR75 73-78, XL80S 80-85, XR80 79-84, XR80R 85-03, CT90 66-79, S90 64-69, SL90 '69, ST90 73-75, CA100 61-62, CA102 62-69, CA110 62-69,