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Old 10-12-2012, 09:02 PM   #16
supershaft
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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.
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Old 10-13-2012, 09:19 AM   #17
R100RT Mark
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So, for the sake of clarity, and my education, what are the specific differences between U.S. late model 800cc and 1,000cc heads?
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Old 10-13-2012, 09:26 AM   #18
Airhead Wrangler
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Quote:
Originally Posted by R100RT Mark View Post
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.
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Airhead Wrangler screwed with this post 10-13-2012 at 10:38 AM
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Old 10-13-2012, 02:34 PM   #19
R100RT Mark
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Originally Posted by Airhead Wrangler View Post
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?
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Old 10-13-2012, 02:48 PM   #20
supershaft
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So, castings the same, just machined differently. Yes? Valve seats in the same position?
Yes and yes.
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Old 10-14-2012, 09:06 PM   #21
R100RT Mark
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Yes and yes.
Perfect clarity. Good to know. Thanks.
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