We just had the clutch basket and a couple of gears replaced and added new gaskets. Was missing a bolt that goes on the cover so it had been leaking out that hole a little bit. Once I added a new bolt and add a little bit of oil it wasn't leaking anymore. We road it for 10min and found it was spewing oil out the hose that comes out of the front of the case (by the water pump) and back into the case on the back end, underneath the engine mounting bolt. Is this a breather and was it just leaking extra fluid, as I may have put to much in or is there something else wrong? What bad would happen if you just plugged that hole?

The hose has a T connector right in the middle before it gets back to the engine. That's where it was leaking, right at the T.

 

Check out the link in my signature. Watch the banshee engine install vid and it explains where all those hoses go. Sounds like you over filled it. It only takes about 1.6qts.

 

You cannot block off the case vents, how much oil did you put in it??