Dan H 965

I bought a project UTV. 2010 Hisun 700. I'm doing a top end rebuild. The prior owner did some shady stuff to this poor thing. It's got a knock and blown head gasket. Piston is gouged and 3/5 bent valves. Standard stuff if you dont know how to take care of your equipment. But while doing disassembly there is a nipple on the back side of the head, just under the exaust rocker arm peep holes. The guy has a rubber hose clamped to it and pinched it off on the other end with a vice grips left undet the seat. I can't find where this is supposed to attach to. The manual shows it capped on the head in the new models and doesnt address it at all on the old models. Any input?