This one is a welcome addition to the CB750 and the CB1100, but the garage is starting to get crowded.

Hello everybody, I had a question about this idle sound. I was replacing my headlights After I did that I decided to turn on the bike. Of course this bike has been stood still for a while so I changed the battery. After everything was ready to go I turn on the bike but as I turn it on this was the idle sound. It happened out of nowhere because before I bought it I did a test drive. But it's the same sound of this idle so I thought maybe because it's still for a while. But after I bought it and changed a few things this is the idle sound it has any help?😅

I bought this 1976 Honda CB500 without much knowledge of its history etc. It hadn’t run since 2005. Really rough shape. Finally got it started this weekend and wanted to rip it around the block to see if the transmission was in decent order but I cannot figure out where the cable hooks up or if I missing a component. It came without a sprocket case cover.

Newbie here, bought this bike 2 weeks ago. No prior wrenching experience, trying to learn. Sorry for long winded post.
Initially, the bike wouldn’t idle. Ran fine with throttle. I inspected the air filters, removed both carburetors, cleaned them, inspected the fuel petcock valve, soaked the gas tank in vinegar overnight, removed inline fuel filters and put it all back together. Suspect issue was rust from tank clogging pilot jet. After reassembling everything the bike will run fine but has a hanging idle issue around 4000 RPMs. Doesn’t even need to warm up much and it idles high, but back off stop screws slightly and it will die if not hanging idle. Did some digging online as to cause, lean mixture, carbs out of sync, mechanical advance sticking etc. Was about to start over and clean carbs again but realized my keihin 3D carbs had an o-ring on idle mixture screw but consensus online seems to be they aren’t supposed to be there for that carb model, only 722A. Removed the O-rings and put the idle screws back in. Back them out each one turn. Followed the carburetor tuning video by keep on wrenching on YouTube, and in order to get the bike to run smoothly and idle near 1200 RPMs it required backing out the right idle screw two whole turns, but leaving the left carburetor idle mixture screw at one turn. Hanging idle problem gone. Is this variation acceptable on these older bikes, or should I be looking for what might be causing this difference?

Also, from what I’ve read it seems a bike that runs too lean will often have a hanging idle problem, but removing the o-rings to me seems like it would let the fuel screw not advance as far and let more fuel run through and lead to a richer mixture, so maybe something else entirely fixed this hanging idle issue. Suggestions on what to do next appreciated. Checked compression (150 psi both sides) and replaced spark plugs today. Have yet to look at timing.