Honda AFP125CRF 2018 Owner's Manual page 72

Drive Chain Adjusting the Drive Chain Slack
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Checking the Drive Chain Wear
If the drive chain slack is excessive when the
rear axle is moved to the furthest limit of
adjustment, the drive chain is worn and must
be replaced.
Chain:
DID420AD2
KMC420JB
RK420SL
If necessary have the drive chain replaced by
your dealer.
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