Part# for tank is SER8135. good luck trying to find. Its the same as the Serpent Impact M2. Take to LHS and try to match it to a 75cctank.

Looking at the HSN & MRN. You got it running rich by HSN. MRN is far in. I'd like to see photo of your LSN. your throttle air gap is probably 1.5+. Know wonder it lean out after 10minutes or idle up. Giving it throttle it would stall out, too lean. Post another photo of your throttle air gap. Its natural at half a tank it would start running lean