Twice now I've put fresh fuel in my 99 WR400 at the beginning of the riding season and fuel runs out the over flow tube. The first time I bought the needle and seat assy. $$$. But the second time I noticed the needle still looked new, so I figure I would try the o-ring on the brass seat. It's just my luck Yam. does not sell the o-ring separate, you have to buy the complete needle and seat assy. To much $ for just the o-ring. After doing some measuring I think the o-ring is a 9mm I.D. x 11mm O.D. w/1mm cross section or width, Viton material. Can anyone verify these dimensions before I give McMaster-Carr $6.85 for 25 of these little guys? I'm hoping the Viton will last longer than the Buna factory o-ring.