[Art]

If I was a gambling man I'd wager any rhythmic knocking/clunking heard in low gears will be a seized drive chain link pin. Drive chain maintenance is a very much over looked service item. The Honda workshop manual maintenance schedule recommendation is to inspect (I) and lubricate (L) every 600 miles with a further reference to page 3-16 which covers drive chain slack, adjustment and wear. The workshop manual continues on page 3-17 onward with drive chain cleaning & lubrication, inspection and replacement but how many of us go there?

Of interest here the drive chain wear indicator is a hit and miss sticker. The correct way to determine drive chain wear is to measure the elongation, this can be done by measuring across 13 link pin centres where:
190.5 mm (7 1/2") equals a brand new straight out of the box 520, 525 or 530 (⅝") drive chain
192.5 mm (7 3/5") equals 1% elongation which is the service limit recommended by most drive chain manufacturers.