Question about KZ1000 fuel tank ventilation system

Today I was diagnosing VN1500 vent system and would like to know if 80 KZ1000 system is different.
I found:
1.Fuel filler cap has check valve (rubber mushroom type) , only letting air in
2.There is metal tube, coming out of tank in the rear bottom.. I cannot see front end of the tube inside tank, but I am pretty sure it ends at very top of the tank next to filler cap.
Rubber hose about 10" long goes down from rear end of the tube. There is a check valve or filter with arrow on it.

Who knows about KZ1000 vent system? This is a serious matter. As far as I know engine can stall or fuel tank impload, if vent system doesn't work.

What do you mean 'front end'? The tube opens near the base of the gas cap hinge. There's a little nipple on the cap that connects to it. The tube is for fuel overflow. What you call a 'check valve' is actually part of a vapor separator. If the tube is clogged the vapor will still vent, but the overflow would leak out of the cap instead of going out the hose as it's supposed to.

Uhh, kz1000 tank cap is vented, that is all. nothing like a modern bike.

And I'd assume the 'filter with arrow' is a charcoal cannister, it takes fuel vapor smell out of the air