kz650 Spark plugs

Can anyone think of why I would have put B8ES plugs in my 81' KZ650 instead of B7ES plugs that the book calls for? I have Dynatech electronic ignition, Dynatech green coils. Also rejetted with K&N cone filters. I'm just trying to figure out if I made a mistake or if I used them for a reason. I rode the bike for years this way. Also any thoughts on Iridium plugs? Are they worth it?

idkleine wrote: ...B8ES plugs...instead of B7ES...Iridium plugs? Are they worth it?

B8ES is a cooler running plug.

Iridium plugs? Are they worth it? IMO, "Nope, not worth it."

Good Fortune!

The 1977 KZ650s (at least the early ones) originally came with B8ES plaugs, and that's what was recommended in the 1st edition of the Kawasaki service manual. However, these plugs proved to be too cold for normal riding and were later switched to B7ES plugs. The later editions of the manuals also were changed to specify B7ES. Having bought my bike new, I ran B8ES for years because I just continued using the plugs that came in the bike plus I was using a 1st edition manual. The plugs were always sooty and sometimes one would foul. When I bought a newer manual and saw the different recommendation I started using ND W22ES-U (the ND equivilent to B7ES) plugs and the bike has not fouled a plug since. That's been about 11 years.