what is a 10.5 compression piston

[250RGUY]

I am trading my R for a 400 ex and this is listed in the mods and I have no clue. This is the first 4 stroke ever for me. 10.5 compression piston???

[nakomis0]

This post should be in the Powertrain forum, but...

10.5:1 is a little more than stock.

Stock is 9:1

Stock on a z400 is 11:1

More compression more power..

Coming from a 2 stroke you should understand compression.. its so much easier to get it on a 2 stroke, just mill the head.