NA-10003 Standard Piston Kit for 400EX

great choice at half the price of wis**

Put together with cometic top end gasket kit and broken in properly. So far runs great

So far so good. I used this in my recent top end rebuild. This piston and a valve job gave me 140psi compression, The piston looks and feels super high quality. My only complaint is that the piston looks so cool but is buried in the cylinder and I can't see it anymore.I did notice the installation was a bit more complicated. (That would be on me though) As a suggestion for those who this may apply: be sure to follow directions on their website, (the rings do have a top and bottom & specific order [obviously], and piston needs to be in correct orientation.) Due to the hemispherical shape of piston, correct timing is critical or valve damage is imminent.

Very good quality , you will need to make sure all rings are in the right position. Used a protractor and I think sharpie to make where the rings gaps needed to be. And she’ll need a good break in period.

Fit and finish was superb, I was hesitant but this piston was a huge power upgrade paired with a cam on my 400x. I am side by side with 450r's

Piston rings were easy to install by hand. Followed break-in process from (...) and it still looks new after a few days of hard riding.

Obviously anyone interested in this piston is concerned with value. While I haven't run the engine, it's obvious this is a quality piece...

Works great. Easy installation.