Modern Buddy

My rat with about 700 miles on it has began to leak a black fluid from where the exhaust meets the engine. I just had it serviced 50 miles ago. There is also a heavy rattling noise that is starting to get worse.What could this be?
I took it to my dealer and he is keeping it for a day, but im nervous and i hope this isnt serious because my damn warranty is void.

I have had 2 cycle snowmobiles lead a gas/oil mix out of the muffler -
stopped on its own... I assume something was sticking & too much gas was making its way all the way through to the tailpipe
Re vibration... could be a lot of things
at the first service, the dealers are supposed to check every nut bolt & screw on it - the are "rattlers"
good luck & hope it isnt too bad

its normal to get a little bit of oil leaking with a 2 stroke. as long as its not leaving puddles everywhere then it fine.