The big hose in his pic is not the crankcase vent, it is the clean air system that introduces filtered outside air into the exhaust ports. The crankcase vent has a much smaller hose going from the separator on top of the transmission to the air box. You are right that it should not be capped. Many folks install a small filter, while others run a longer hose either toward the ground in front of the swingarm, or toward the rear of the bike under the tail piece.
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough
