Carburetor Information
U.S. CB750 Models 1969-1978
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Measuring Float Levels
There is no need for any special tools, divining rods, or magic chants. A simple cheapie dial caliper that can do metric is enough. For the PD series "keyhole top" carbs the float levels are 14.5mm (stock 77K PD-41A is 12.5 but for our rigs 14.5 works fine), and 26mm for the earlier "round top" carbs. As long as the caliper has the deptch gauge on the end you'll be fine. Actually anything with a right angle that is the correct distance from the end to where it bends over to touch the bottom of the float will work.

The carbs should set at an angle where the floats just barely rest against the spring loaded pins of the float valve needles but not leaning enough to where the weight of the float compresses the springs any but no so little that the floats do not keep the float valve needles seated. Above the floats are being set to 14.5mm for the PD series carbs measuring from the bowl gasket face.

Above I've made a makeshift stand so the earlier style carbs remian at the correct angle while setting the floats. Each lobe should be 26mm which means you may have to twist the float assembly just a bit so both lobes are even. Use a very small flat screwdriver to bend the tabs resting against the float valve needles one way or the other. DO NOT bend the arms the float lobes are fastened to! If the floats are cockeyed in the least they could rub against the casting or float bowl gaskets and you'll have a runaway puke tube. Levels are measured in the same way as shown for the PD series except the measuring tool rests on the edge of the slot on either side of the bowl gasket lip (see below).

Here the notch you measure float level from is highligted. It is incorrect to measure from the gasket seat/face as some sources suggest or as how the PD series carbs are measured.


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