chain slack
 

just had a look through my bike manual and noticed that the chain slack reads 40.0 -55.0mm (1.57-2.17 inch)

My last bike only needed approx 35mm slack.......

Any thoughts please i have trawled through the forum but not founf a definitive answer for the xt660x i'm a little concenred not to tighten it to what i'm used to due to the extra wear and tare etc...