Not a good Idea to run with the short reach plugs in, they will foul faster, the exposed threads will just crud up on you, generally just make a total bodge of things. Another thing the guys here in the states are doing, because our fuel is so crappy, is go from factory recommended heat range of B-8ES, to B-7's , or even B-6's, however my 62 RGS runs better on the Bosch plugs, (they even self clean better) NGK anymore is a crap shoot for getting any quality in their plugs. My bike also likes the cheapest made spark plug on the planet, it runs great on Champions ! !
It has to do with the way that the porcelin part of the plug is swaged in to the metal housing, it does not have a narrow lip down inside of the plug that can catch the unburned combustion particles, and short the plug out. NGK's foul way too easy, plus you might get one brand new one right out of the box that is a dud , their quality control has gone out the window. I have better luck with Bosch and even Autolite plugs.