crankcase cover srcew oil leak
 

I noticed there is a slight weeping around the bolt (left hand side of engine).
There is no dripping just a wet look after riding.

I hand tightened the screw (1/4 turn), helped for a while but it is back again.

I guess changing the rubber o ring would be the next thing to do.

My question is do I need to drain the engine oil first?
thanks