Lean cylinders?

[Gumby 1100_imp]

I think that it is just the nature of an inline, air-cooled, four cylinder for the inner cylinders to run hotter. They are not getting the same air flow and they have less fin exposure to the air.

My inner two header pipes also tend to blue a bit more than the outer two (especially at the top edge near the flange). Some OptiGlanz and some Autosol metal polish usually takes care of the discolouring for a few months.