Re: Popping noise coming from exhaust and also..
The circular thing is probably the VOES switch that changes your cruise ignition advance. It has a vacuum line on it that goes to the carb. You may have a vacuum operated fuel petcock also, not sure on that bike but look on the back of the fuel petcock and see if there is a vacuum line on it. The other would probably come from the carb. If you are unsure the dealer can show you a diagram that would clear it up for you.
I've encountered this same-thing on 2 bikes over the years both had replaced the ignition with aftermarket ignitions and felled to remove the VOES system completely and just plugged off the line going to the VOES switch. after a few heat cycles and the constant vibes the plug falls off and the bike runs like crap because of the lean mixture created by the open vacuum line.
"It's just a tool box, you pick the tool for the job". "Myself I like the ol' 1911 45." (Sam, Ronin)
"I know because I've still got the shovel" (Man who knew the real story)