Drill Out an Orfice
From: https://www.youtube.com/watch?v=Hl15-Zk5pmc

Gas Orfices
Natural gas normal pressure is: 5.5 WC
LPG pressure is: 11.3 WC

Since natural gas pressure is much lower than LPG, NG orfices must be larger to get the desired flow of gas.

Note the chart: Gase Orfices


SIZE:
1-1/2" blue flame above burner