86 350x rear axle oring question

[ctk]

replacing rear axle bearings and o rings and such. Service manual shows a o ring that goes on the rear axle by the chain sprocket. Inside by the carrier. There seems to be no groove for this o ring. I have a o ring kit and found one that seems to be a correct size. When installing the axle it just doesn't sit right with the o ring. It fits right with no o ring. My question is, is this o ring just for the 85 350x, if the 86 needs one anybody know the correct size? What is the purpose of this o ring? The parts diagram on bike bandit, service honda show no o ring. The service manual seems to be written for the 85 350x with some add ons for 86, thats what makes me think its a 85 only part. My 86 350x did not have this o ring when I dissassembled, not that makes it not needed. Thanks for the help, again these questions are for the 1986 honda 350x