On a GPX 250 I've been riding for about 4700km... Had a 1000k service before I bought it. Should I have 70+mm chain slack? Most of the slack is up... I pull it down maybe 10mm but up it moves heaps. I'm about to take it in for a major but I'm curious if the chain should be this far off spec. Never thought to check it before yesterday. Spec is 30-40mm.