Chain Slack

[VERIFY] What is chain slack? Chain slack is the free play in a chain-drive motorcycle's drive chain, measured as vertical movement at a specified point on the lower run. Too tight and the chain loads the countershaft and rear wheel bearings as the suspension moves; too loose and it can slap, wear sprockets fast, or come off. The correct figure, the measuring point, and whether the bike should be on its side stand or loaded are all model-specific — use your own service manual, not a number from the internet.