Funny, but I've had some guys tell me that the o-ring doesn't really need to be there. Guess they think that it's too small to be important. Wouldn't be in the design if it wasn't important.
I also think the clone saws don't have that o-ring as they also don't have the red sleeves for the carb bolts. Both are problems waiting to happen.
If you use a sealer of some type it seals too. Like Threebond 1184 1194 yamahobond etc etc etc. But for $3.99 I just prefer to not be cheap and stick the o-rings in. JMO.
First thing I do when I get one is go through them. O-ring was installed before starting.
Never caught they did have the red sleeves. Hmmmmmm.
( I have found folks in small shops using rolled up paper in there before to take up the space ) . I always installed the oem red plastic tubes in place myself.
So is the only purpose to take up that slack space for movement, least my thinking to keep it steady.
Never had to pull carb off though.