Below is a copy of a page in an official 70s Honda sohc four service manual. I put a copyright mark on it so that questions that arise from its copying on the Internet can be answered. This page describes adjusting the vibrating point type "mechanical" charging regulator that is part of the charging system on all of the smaller 70s Honda fours as well as the 750 fours' first few year models. Note the absence of justification or symptom or any other qualification or restriction. This is a normal, legitimate adjustment.

This mechanical regulator (as opposed to the later electronic type) works as follows. The magnet in the bikes' charging systems is an electromagnet, one whose magnetism can be turned on and off, as well as strengthened and weakened. The on/off aspect happens when the regulator's contact points close (on) and open (off). The strengthening and weakening is facilitated by the points opening and closing rapidly--"vibrating"--to produce an intermediate state between on and off. Many of you may recognize this as a quaintly archaic version of what electronics such as transistors and IC circuits do today. This type of regulator was once common in cars too.

The regulator has a leaf spring that together with a relay winding determines how long the points stay closed. This spring can be given more or less tension by turning a small screw (shown) on all but the 350/400, which lacks the screw and is instead adjusted via pliers. Increasing the leaf spring's tension increases the time the points stay closed, thus increasing magnetism and hence charge output. I like to turn the screw inward until only two threads are visible under the screw's head. This is approximately 3/4 full rate. Given the smaller fours' almost minimalist output, adjusting should be considered a routine part of maintenance, This is factory, it is not hack.