Alright thanks much!

Hello all this is my first post so i apologies in advance if I'm in the wrong place or if I'm doing this right. . . But I have Trail fire with (S# J340FH S#098416m D.O.M 09/78) My question is Part Number M66518 Qty Req 2 Part Number M66519 Qty Req 1. When i pulled my secondary off i had 1 of M66518 ...