piston comparison:honda-briggs

[scratchbuilder]

The one on the left is Briggs 2hp. On the right Honda 2.5....how can Honda claim 2.5. The Honda is a g100 flathead. Briggs is old flathead.

 

[MEASURE TWICE]

The throw of the piston also is a factor. But even if the throw from the crank leaves the displacement the same, there is head space that is a factor in the overall compression.

Mostly though is the porting is better and I was amazed as the roughly 120 cc old 80's era Briggs at 3hp compared to 90's era Yamaha 125 at 17hp trail bike had me taken back.

MT

PS
Forgot also over head cam may also contribute as far as that trail bike both similar displacement 4 strokes.... 5 times the horse power