One of my maintenance goals is to repair in such a way that no one could tell I was inside the machine, including when it was looked at inside again in the future.
Kind of the doctor's credo of "do no harm". I've met others that have this same ideal. If you have the right tools and know how to use them, leaving no trail or tool marks is possible.
If the mid range and/or top throttle positions are too rich, fine tuning the pilot circuit will be of little help. Assuming the mid and main are delivering to the bike's needs, the pilot is tuned for reliable throttle response off idle under full load. It should accept up to one half remaining throttle travel in any gear under full load without hesitation. No, it won't be powerful during this test, at least until the RPM can come up and the engine can get on the cam. Anyway, for these carbs, the pilot screw is adjusted for throttle response, not max lean. In fact just the opposite, pilot circuit is set over rich, so when the slide is lifted and the fuel flow reduces, the prior over rich condition allows the engine the pick up RPM.
I've done the experiment with this carb style and reported in prior posts.
I have an exhaust gas analyzer which I previously used to fine tune auto idle for minimum emissions. (This was almost a mantra for the 80s/90s.)
Seemed logical to apply that to the Cb550. So, I tried it. In the garage with the door wide open. I pushed the exhaust sniffer into each tail pipe of the 4 tips (74 Cb550) and tweaked the pilot screw of each carb for leanest tailpipe emissions at idle. The resulting setting was 5-6 turns out from seated which surprised me. Had to keep turning down the idle knob (less and less air past the slides) to keep the idle speed from climbing. I must of spent a good hour doing this balancing act with each of the 4 carbs. The engine simply purred on the center stand in the garage, but was a bit touchy on the throttle to bring up the RPMs. Time for a test ride. I didn't make it 50 ft until I knew what I did was flat wrong for this bike. Only throttle advance twist of 1/8" or less allowed the engine to pick up at all from low RPM. I painfully nursed it back to the garage and started turning the air screws inward 1/2 turn at a time and turning up the idle knob to keep proper idle speed, then drive for effect. Slightly less sensitive throttle. Bring the screwdriver with, drive and tweak, drive and tweak, until I can give the engine one half a twist from idle, even in top gear, and the engine behaves on command. Back in the garage I now check the pilot screws setting, and they are right at Honda's book spec for setting. And yes, it does run a bit rich at idle. The plugs clean off when the engine is in its power producing range where the slide and main are the dominant mixture providers. Idling rich is to compensate for lack of accelerator pump. On those carb types, you can set the idle for max lean.
Older machines are not tweaked like modern ones, and many have "special needs".
See this thread for other engines with special needs:
http://forums.sohc4.net/index.php?topic=139897.msg1584202#msg1584202
