Scott, that's a good video and to the point. I've stressed multiple times in this forum to check the O-rings around the main jets fit well. You're the first to give feedback. However... I doubt that is the cause of your hanging idle. The correct idle on these CB500/550s consists of several things that have to be set right. Starting position should be what Gruzzel has depicted. BTW, I know him as very gründlich although I will never advice anybody to separate the carbs from the rack. Also I have never understood that picture (Fig. 5) Honda put on p.8 of the Shop Manual CB500-550. I have ignored it all these years, also because whenever I synched the carbs (maybe 3 times in total over 40 years!) a little tweak was all that was needed anyway, so my adjuster screws stayed pretty close to where the factory had set them. Yours look way off. I give you a good chance that once you've started from the right position, you will be able to cure the problem. Another thing I must warn against (although you probably know it) is to go for a highest possible idle by turning out the airscrews and then restrain the rpm by the big central idle adjuster. No doubt you will get a wonderful idle and have the engine pur like a kitten. But... driveability will be poor. These oldstyle CB500/550s need a idle that is a combination of somewhat raised slides and then have the rpm restrained so to speak by air screws set on the rich side. It may sound counter intuitive, but it has always worked for me. After all these are simple carbs that lack acceleration jets.
