How to adjust a motorcycle chain is a low-difficulty, high-intent query: 390 monthly searches, KD 0, because the job is in every Japanese owner manual and still gets skipped. Park on a stand, find the tightest spot by rotating the wheel, and measure slack at the midpoint of the lower run.
Typical street spec is roughly 1–1.5 inches, but the number in your book wins. Loosen the axle nut, turn both adjusters the same amount, check the alignment marks, torque the axle. A crooked rear wheel eats the side of the sprocket.
Lube after a wet ride, not a dry dusty one that turns oil into grinding paste. O-ring and X-ring chains do not want heavy gear oil packed into the plates. Replace chain and both sprockets as a set when you can pull a link off the teeth or see hooked teeth.
A 520 conversion is a weight trick, not a maintenance skip. If the chain is rusty orange, stop stretching it and buy a kit.