300ex motor questions??

[SnotMe80]

i have a 98 honda 300ex. my question is when your sitting on the bike it would be the right side of the motor-if you look at the top of the motor there is a round rubber piece on the side about the size of a half dollar. their is a little oil leakage their-just a slight bit-not even a drop but there is dirt their were it has clung their and the rest of the motor is clean so i know it is leaking every once in a while? what is this piece? how do i fix it? what do i need to do? the bike runs fine with no problems.
thanks
Rob

[300exazzkikr]

the timing chain gear is right behind that rubber piece. to stop it from leaking you can take the top of the motor off, not the head. and put a liquid gasket around it. It happens to a lot of 300s. It's simple to fix. See the picture.