Regarding service manual :

1. Measure 15 section of chain - length limit 240,5mm (9.46 in). (while measuring push down drive chain to increase tension, measure the length between 1 and 16 links). If longer - replace chain.
2. if see any stiffness, some links stuck and lubrication doesn't help - replace chain.

If sprockets are worn or bent - replace chain and sprockets as set.