This is simple conversion for your NT carb to 58mm racing filter. \it results in better air intake and better acceleration. Don't forget check your spark plug after testing it, if it didn't change the right air fuel ratio.
https://www.ebay.com/itm/Blue-60MM-Air-Filter-for-Carburetor-2-Stroke-Motorized-Bicycle-49cc-60cc-80cc-/282626068253