My experience was very similar to yours, after I had 'done' my carbs and was trying to dial them in.
Bench synching, by setting the plates using idle orifices as references , was less than a success for me. Using 1mm. surgical wire, I would slip it under the plates & then move the adjusters just enough to allow it to pass. Trouble was ( I later determined) the wire was raising, slight, ridges on the plates and putting scratches on the carb floors, as it passed. Even if I was mindful of how much pressure was being placed on it. Both errors stopped the plates from closing completely. The plates came out, again,the imperfections were addressed and I tried another method. It solved my issues: As the carbs were still off, I pulled the slides out, and backed the idle adjuster completely off ( now is a great time to verify your fast idle adjustment too). Starting with #4 and working out to #6, I placed a bright light source ( a Luxeon flashlight) at the carb throat. The individual synch adjusters got backed out enough to allow their throttle plates to close irrespective of their neighbors. Throttle plate retaining screws were loosened & their plates 'snapped' closed a number of times (gently, but firmly) to make absolutely certain, they were perfectly aligned in their bores.... no light was getting past. The screws got another, light, application of Loctite blue. Manipulate the idle adjust screw so that the #4 plate is just closed. Working out to #6, set the adjusters so that the plates are all just closed. Similarly, work out from #3 to #1 & repeat the same proceedure. After all the plates were set in this manner, when the idle adjust screw is moved to open the throttles, all the plates can be seen to be opening at the exact same time( they all allow the light to just pass). You can make slight adjustments with the synch. adjusters at this time. Conversely at this point,with the idle ajuster completely out, no throttle plate should be seen to be allowing any light to pass. Button the carbs back up, slap them back in, and do a proper synch., That's what did it for me
From my experience, and as many others on the board have mentioned, there are no half measures when doing CBX carbs. 'Good enough' won't fly. I have never worked on a motor that is more sensitive to carb set-up!
I sure hope this is heplful
) time that they were off, the light showed how wrong I was. Even if they hang open a,seemingly,insignificant amount, that will be enough to create the symptoms you are experiencing. An absolute baseline has to be that when the idle adjuster is backed off, there is no possibility of air finding its way past any of the throttle plates. You cannot correct for this,after the fact, with the synchro adjusters.
