After reading the various posts on Iridium spark plugs I thought I’d take the plunge and invest in a set. However, I’ve gone for BPR6EIX which is what NGK recommend.
When I took the old plugs out there is definitely an issue with the bike running lean with the exception of number 3. Bike has covered around 600 miles since going back on the road last summer. Haven’t used the bike much this year as British weather has been pretty rubbish. Engine wasn’t stripped down and just had the usual checks like compression, valve clearances, cam chain etc. The carbs have been rebuilt using scotch’s cleaning tool with new idle jets and new floats. Also installed new ‘O’ rings to the idle mixture screws. Haven’t had a chance to put the newly acquired colour tune to the test so that will be the next job. Bit concerned about number 3 though.
I would not worry until you have done a full Colortune procedure on all 6.
For your information, the K Manual is wrong when it states setting the mixture screws at 1.75 turns OUT from set..............it needs to be at least 2.5 to 3 turns to start with and adjust from there.
Also just noticed you have 3 SILVER plugs and 3 GOLD Plugs.
The SILVER ones are made in Europe and not as good quality as the GOLD original ones made in Japan.
I would either change them all for GOLD type or even better invest in a set of 6 NGK Iridium Plugs which will last you forever.