I inherited this bike and I am going to finish.
I built an oil tank with no filler (thinking I could top off through the return line.)
This engine is new factory engine built 10 years ago
bike has always been inside heated garage
UNFIRED
something tells me I need to vent the tank to atmosphere even though I have been told otherwise

The top two lines are vent and return from oil pump, the bottom line is for feed
VENT OR NO VENT?????

 

Oil tank must be vented. It connects to the engine case fitting above the oil pump in the last photo. With the wide spread top entry fittings in the tank, I'd recommend you use the the left side for oil return and right side (carb side of engine) as the vent connection. I'd work either way but all things considered, that'd be the safest routing. You don't ever want the vent below the oil line.

I can't make out what carb that is and cannot tell if the engine breathers on the heads are plumbed to vent correctly. May be fine, just can't tell from the jiggled photo # 1.

 

You are going to want a tank fill, it also gives you the ability to see how much oil is in the tank and if the oil is returning to the tank when you first start her up. Your bike, but I recommend. Good luck.

 

Buy yourself a PVC pipe cutter like this to cut your hoses..