[fast1075]

Sounds like the carbs still have problems. Do all four cylinders have fouled plugs? Remember, even though the carbs are connected, each one controls it's own cylinder.

If it runs ok at mid throttle, but has problems only at idle, the air bleeds and pilots or the passages are plugged still. By the 80's I had moved on to Kawasaki, so direct help for the carbs.

The sync ports most likely have screws in them. You remove the screw and install a special tap that connects to a vacuum gauge. My sync tool which I have had since 1971 uses 4 gauges to monitor vacuum on all cylinders at once. You adjust the carbs first to get them even on vacuum, then adjust the idle mixture, and readjust for vacuum if the mixture adjustment changes the idle vacuum.

If it was mine, I would pull the carbs, remove all the jets and give then a nice long bath in 50/50 pinesol/water. Three or four days at least. When you clean them out. Get several cans of brake clean and check to make sure it goes thru the transition ports (the tiny holes in the carb body near the throttle blade when the throttle is closed) if these tiny ports are plugged you have problems.

The idle circuit is the hardest to get in order because the orifice sizes are so tiny. The air bleeds which get the air from the carb inlet must be clear. The idle circuit needs the air emulsify the fuel at idle.

Way back when, a company sold a kit that used a log manifold to mount a single carb, and was popular with some that only toured, and didn't care about performance because of the hassle of keeping four carbs in sync.

I did the exact same thing on a KZ-440 that had set up and the carbs were ruined. Ran it with a 34mm Mikuni. I'm not suggesting this, just a view "outside of the box".

Get the cabs clean, and if it is not an oiling issue (ring seal, etc) you will be fine. Those old Hondas are tougher than a concrete block.