This motorcycle has more miles on it than most baggers runnin' around here. It's been together for 12 years now, and the head has been cracked for 10 . . . the extra air keeps my mixture a bit cleaner on the rear cylinder, and evens out the jetting. If I remember correctly, this cylinder has a +.006 tapered spot in it too. The pistons are +.070 (last hurrah on this one) and I just decided to run it. It's my own bike, so I have the authority to do that . . .
The plugs always read the same. A little more oil detonation(that's what I call it) on the rear, but not bad. The head is cracked so bad, the blow-by oil wicks it's way around the outside of the sparkplug insert, so I run a big, copper washer under the plug to help stop it - and seal the plug. When the motor gets hot, it kinda seals it up. I have some different heads, so I'll try those. You know that K-Models don't use head gaskets - precision engineering ! Try that on your Evo !
(PS. 6.5:1 compression may have something to do with it?)