[bandito2]

Ahh.. Your last message came out while I had still been pecking away off and on at my response.
Low miles on this bike? There may be >some< metal flakes with the first oil change in a new transmission, but not much. Oil is silver grey? that is worrisome unless something other than standard hypoid gear oil was used. (I have no idea what could be used that would give that color.) I have had no experience with a transmission that has failed, so I'm not sure how things might actually look. Moisture would have more of a tendency to make it look like coffee with just a little cream.

Did you notice if the drained amount was much less than the amount used to refill? or was it about the same?

Noise only when clutch engages? AND still makes the noise when rolling the the rear wheel while engine off? It's not the clutch then. From your description It would definitely indicate a problem in the gears and/or bearings. Metal flakes in the used transmission oil makes the transmission highly suspect. Especially if the oil had been too low.

Not sure of this Linhai model transmission history, but on Honda Reflex for example, the final driveshaft bearings can cause noise from being worn or loose and be more probable than the gears or their bearings as long as transmission oil has been adequate.

Noise in the transmission would come from worn, seized or chipped gears or from worn or damaged transmission bearings.

Do these and test before you tear into the transmission:
1) make sure rear axle nut is torqued properly.
2) make sure right side swing arm bolts to engine are torqued properly.
3) make sure the shocks are fastened securely.
4) make sure rear brake is not dragging.
5) X - OK, presumably you've done this already -> proper level of transmission oil.

One can hope that simple things will be the fix. (they do happen from time to time)