The first picture shows where the float needle sits, conical tip in the float valve and it rests with a tiny spring loaded pin on a tiny brass tang (seen on the right in pic 2) of the float. That tang can be adjusted to change the float level. My advice: don't. In all those years I have never encountered a CB500 or 550 that needed to have it adjusted, where as in this forum, it's... well epidemic. I was curious the other day and checked mine with a cleartube (principle of communicating vessels, we call it) for the second or third time maybe in 37 years. The levels were spot on, but I must add that I have the original length and diameter fuellines and no 'extra' inline fuel filters and that I'm confident the float needles do not stick and the ventilation is OK.
The carbneedles inside the needle jets, which are much longer and that are responsible for the gas mixture say mid throttle cannot be seen unless you remove the main jets (the needles pointed ends are right above them). You can get at them from the carbtops after removing the toplids and after removing the slides. My advice: don't. Even with aftermarket exhausts there is little chance you'll ever need to reposition them. Aftermarket exhausts used to advertise: NO rejetting required and so it was and is. Too many believe that because it's described in manuals like Clymers, it has to be attended but these manuals happily fill pages with what they have copied from other manuals that they've published before. The practice may be necessary for other bikes but in everyday practice of the CB500/550 it is not needed. If you want to learn more about your carbs, go to
http://forums.sohc4.net/index.php?topic=17788.0 : and scroll down to: Honda CB500 CB550 CB 500 550 Workshop Service Repair Manual 1971 - 1978 Part 10 p.175.
