do some years not have the rubber o ring? i went into mine and there was no ring and when i put the zip tie on it seemed to run worse....then i fooled around with it for a bit and got it to work pretty good. the one thing im worried about is the zip tie popping off the linkage but as long as its tight it shouldnt be a problem.
That o-ring was put in there by someone, it was used instead of a zip tie or safety wire. The zip ties/wire will hold it tighter and not stretch like the o-ring probably did. If you are worried about the tie breaking try using some wire.