Believe me, it's lean at 58. Anything less than a 58 and I can't make it out of the driveway. It's a real touchy beast. I've gone down to a 54. The bigger the jet, the slower she goes. The peak speed is at #58, but the acceleration is off. The bike will accelerate OK with the 58 if I don't floor it, but if I do, you can definately feel the bike bog out. I have to overcompensate with a richer needle setting, but it is no longer smoothe throughout the throttle range. It's all over the place.
I've done the plug chop thing. It's slightly dark with a 60 and a bit pale with the 58.
One thing I seem to remember that someone told me years ago...maybe there is some truth in it, maybe it's BS. I've been told that the reason that BING jets skip to only even numbers is because the tolerance was a bit "lax" on them. You could have a "lean" 60 a normal 60 and a "rich" 60. They couldn't get them close enough to call them a 57 58 59 60 61so they jumped to every other one. In other words a rich 60 was closer to a 61. Maybe I have a rich 60 or it's been tampered with.