I have recently acquired a very nice 2002 Monster M900ie, low miles and in very tidy condition. The plugs are NGK DPR8EA, the same sort of grade as all the current spares suppliers quote. The Haynes and the Owners Manual, 14 years ago, specified something like a Champ RA6, a grade hotter. Now - the only thing, in this bike's world at least, that has changed is the formulation of the fuel. Does this explain the change to a colder grade I wonder ?
Dave I have always thought hotter plugs for shorter runs, but that’s on my older classics, then longer runs colder plugs. I will have a look at my 900ie when I get home and see what has been fitted.
The DPR8EA is the closest NGK alternative to the Champion RA6. I always ran my carbed 900SS and 907ie on DPR8EA-9 with no detrimental affects. The -9 plug has the gap preset at 0.9mm (35 thou), this helps prevent plug fouling
I guess that I assumed that the various companies used the same heat grade numbers, with different prefixes and suffixes to denote tip types, sizes
