Planet Minis

gman

Here are some comparisons number between Early 80's XR 80 (left) and mid 90's XR 100 head (right).

I'm under the impression that these castings didn't change through the years, Only model specific. The newer +01? heads have a intake valve seal too.

Intakes:
XR 80 diameter .880" runner volume 22cc
XR 100 diameter .990" runner volume 29cc (this head has light porting for intake matching)

Exhaust
XR 80 diameter .910 runner volume 14cc
XR 100 diameter 1.025 runner volume 16cc

Chambers
Visualy the two head combustion chambers are radically different. The XR 80 chamber looks huge, next to the 100. However, Both are right at 9cc..

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