@Bilbo9000 Sorry to tell you what you really don't want to hear but that spacer fits between the cases and the lower rear engine mount bolt passes through it (items 5 and 6): https://www.fowlersparts.co.uk/parts/4105067/dt125r-3rm5-1993-999-a/crankcase Not sure what would happen if you leave this out; it has a rubber vibration damper either side of it (Yambits sell those or item 4) so I think this is to stop the inner parts of the vibration dampers being pulled towards one another when you tighten the bolt. It could potentially also pull the frame mount out of line as without the spacer present, there's nothing to stop you just tightening the bolt more and more. End of the day Yamaha put it there for a reason so I'd bite the bullet and get on and do it. If you've just assembled your cases this will test your Anglo-Saxon vocabulary to its absolute limit (as it would mine) but you're not the first and won't be the last mate; archaeologists have found rectangular boulders of the same stone used to build Stonehenge (these were quarried in South Wales) at the bottom of the Bristol Channel so imagine how that guy felt...

@Sgt-Robuck-5, I have the same scratches but there is also metal in my oil, do you think the metal could be frome the scratches on basket or my transmission?

You'll want to understand why that's happened before restarting the bike. Lack of oil, incorrect piston ring end gap tolerance, or just generally tired engine, etc.