The need for adjustment may not become obvious, and a slack belt is capable of driving the dynamo without much slip at slow speed so that a small charge may be indicated. As the automatic voltage regulator reduces the charge rate when the battery is fully charged it may be assumed that the battery is well "up", whereas it may be seriously discharged. See also page 70. The belt tension should therefore be checked reasonably often.
To adjust, slacken the dynamo clamp bolt (illustration, page 34), and rotate the dynamo in the strap until the belt is reasonably tight. Do not overtighten and do not move the dynamo endwise and put the pulleys out of line. Tighten the clamp bolt when the adjustment has been completed.