uneven chain tightness

[keratos]

When the chain is at its tightest there is around 5 mm of play but when its at the slackened part there is around 15-20mm of play.

the yam service manual suggests 30-40m of slack is appropriate. your chain , on this basis, is dangerously over adjusted to the point where it is "too tight", may cause wear in the drive mechanisms, snap the chain, wrap around your wheel and stop the bike ! not something one would want to occur at speed I would imagine - perhaps the more sporty risky lads would find this exciting - I wouldnt.