Originally Posted by R100RT Mark
So, for the sake of clarity, and my education, what are the specific differences between U.S. late model 800cc and 1,000cc heads?
From '85 on, I believe it's just combustion chamber diameter. Depth is the same, I think. Valve sizes are the same.
EDIT: I'm a visual person. This is what a section of the two heads superimposed on each other would look like:
Dark grey is the R100 head. Light grey is the cylinder walls. The red is the extra material present on r80 heads. The bore difference is shown to scale. The chamber depth and profiles of the squish band areas are not, but are close enough to show the general differences.