The hose that terminates under the hood is the breather for the gearbox.
If it drips oil then either the box is over full, you are overheating or you have a leaky crankshaft seal.
You need to drain the gearbox and refill with 650ml of oil.
Overheating can be caused by an air leak making a lean mix!
I also recommend that you sdo a leakdown test.
If you have been riding without an air filter or a bit of rag stuffed in the air box, it is very possible you are overheating, and doing heaps of damage to the top end.