Are you talking about the oil drain plug? If so, you likely just need a new drain plug washer.
EDIT: Nevermind, I think I misunderstood your question. Read it too fast, thinking no matter how much you tighten, it still leaks.

 

after replacing the oil did u overtighten the oil sump plug? did it feel a bit too weak , the yamaha manual says to tighten at 42mn ii went to a honda dealer and he says its way too much as the oil sump is made out of very light and weak material 20nm is enough,.
anyway i think u threaded the sump, need to get it helicoiled, if u get it helicoiled make sure its not too long as next time u drain the oil, a lot will be left in the bottom pan due to the heli coil being toolong and covering the gap,

 

I'm assuming that getting the part helicoiled is not a do it yourself job.....

what will be the damage out of pocket??

and how long should it take when brought to the dealer....

 

if you get it done by the dealer,its gonna cost more than finding a replacement on fleabay...unless you"re in a hurry.