Sitting in the seat, looking down to the engine from left to right, NGK D8EA #1, #2 & #3 cylinders and NGK D7EA (one grade hotter) in #4, for some reason, it always used to fowl up (black, sooty, dry deposits), but since the switch to the hotter grade plug, the problem seems to be solved.
I asked the spare parts shop guy about Iridiums once, and he had a set for my bike "instock", and he said that they aren't any better than the standard plugs, but the downside is they aren't really adjustable and they wear very quickly.
A "bloody bad waste of good drinking money' he reckons considering they are almost four times the price of a standard plug here.
I remember about 20 years ago Nippon Denso had some really good, motorbike plugs out, called "Hot U's", they had a "U-shaped" channel in the grounding electrode, that supposedly fattened the spark, but I haven't seen them around since then.
I use NGK BP5EY spark plugs in my 20 year old car, that have a "V" notch in the centre of the electrode they seem to work the same as the "Hot U's" by supposedly fattening the spark, they seem to make the engine a bit more responsive and the current set have been in the engine for over three years now, (I've used them for ten years). They have worn very little and they have never missed a beat, and they have always been pretty clean when I pull them out to check them every service.
Mick.
