Specific questions - 800cc to 1,000 cc

[supershaft]

All the BMW's heads/pistons have a squish band. The earlier ones are square with the bore and the later ones are angled. The squish band is the flat or angled area of the head before it dips deeper into the more hemispherical portion of the compustion chamber. It will all become clear when you put one of your heads on both size cylinders and look at the combustion chamber through the bottom of the cylinder. A piston's view of the situation so to speak.

[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?

[Airhead Wrangler]

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.

[R100RT Mark]

Originally Posted by Airhead Wrangler

From '85 on, I believe it's just combustion chamber diameter. Depth is the same, I think. Valve sizes are the same………

So, castings the same, just machined differently. Yes? Valve seats in the same position?

[supershaft]

Originally Posted by R100RT Mark

So, castings the same, just machined differently. Yes? Valve seats in the same position?

Yes and yes.

[R100RT Mark]

Originally Posted by supershaft

Yes and yes.

Perfect clarity. Good to know. Thanks.