I installed the NGK BPR6ES today. With a little grease on the threads it hand tightened smooth as can be. The OEM Bosch R6 plug was rough to get out with ratchet and plug socket. The black Bosch tip verifies what the dyno test read regarding the air/fuel mixture. Would a hotter plug be a better thing to have in there?
Feels about the same to me so maybe your original plug was dodgey. I'll report more after it's been in a while. Scott
My plug gets black like that round the rim and the first couple of threads, so do the plugs on the other bike. I'm told by those who seem to know that this is fine as long as the business part is a nice tan colour, which it is.