Hi, My dad asked me to help him change his front sprocket on his 01 dr 650. I know this a simple job, but I ran into a snag. There is a keeper and rubber o-ring in front of the factory 14 tooth sprocket. The replacement sprocket (13)is to small to use the o-ring and as a result pulls the sprocket up to the keeper and the chain rubs on it. Is there a smaller o-ring or is this unavoidable, I am afaid chain damage could result. Thanks for any replies.