All my Ts125/150 powered Mz's all used (one still does) sound like a couple of bolts are loose inside the clutch side. As far as I know, there is no adjustment of the transfer chain. So they all rattle like crap. If you fill the gearbox with any oil other than Hypoid Sae90, it gets worse. I. E. like there is no oil in the gearbox at all. If your clutch has become very sloppy, the chain may be worth changing. Or the bearings, if you decide to investigate further. Have not driven my Ts125 on the road since 1990, but in my trips around my lockup, you cannot differentiate any sound over another one (unless it is sitting still ticking over).
As it is very archaic. It was never the smoothest of gearboxes, although when new and unhindered, it sounded much, much, much quieter than today. As it sounds like a tractor