Like Buttcan said.. it helps to get every last drop out of the tank.. But theres not always that much pooled on the other side.
But more so.. back when the tank was made there was a lot of of these 4 cylinder bikes being chopped.
The two smaller petcocks allowed you to feed both outlets in these banks of carbs.
When they have one bung, then you have to use a T and more clamps and hoses .. This is a neater setup.
I see you have a 77 donor.
If you use the carbs that came with that. you'll only need One petcock for the 77-78 carbs.
As for the brand of tank.. I don't believe thats an Amen tank..
The ones I've used and seen have the cast cap right in the middle with the peak going through it.

Build it the way you want it ..... then learn how to ride it like you own it..
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