I once compared the BUHW and BUHW-2 spark plugs. The BUHW-2 had a slightly thicker ring electrode. That seemed to be the only difference.
I do not think it makes a large difference, because my '73 850 and my '77 1500 shared ign systems, pistons, carbs and a whole lot of other parts, yet the 850 spec'd BUHW-2 and the 1500 spec'd BUHW plugs.
I do not think it makes a large difference, because my '73 850 and my '77 1500 shared ign systems, pistons, carbs and a whole lot of other parts, yet the 850 spec'd BUHW-2 and the 1500 spec'd BUHW plugs.