Anyone run a '12 piston in a '07-'09?

About to do the top end in my '07. I picked up two '12 kits (all OEM) because the '12 piston appears to be higher comp and are much cheaper than aftermarket.

Anyone running this piston in the 1st gen engine? Would save me hassle of installing and measuring squish and PTV clearance if there are known compatibility issues (yes, searched. No result)

Compression didn't change and is still at 11.7:1.  I personally haven't done this but been told it's a direct drop-in. I decided to go with an aftermarket when I was looking. It is well worth the cost for a CP 13:1 piston vs. stock, performance and quality is great! Honda racing recommends the high the better for this motor.

Edited by weantright


Took both bikes apart for a side-by-side comparison. The difference the the '12 head is in the combustion chamber; un-shrouded more around the valves. The piston dome is higher to make up for the increased chamber volume. The '12 piston dome interferes with the '07 combustion chamber on the squish pockets between the intake and exhaust valves

I tried to get volume measurements for comparison, but didn't work out as well as I wanted.
ImageUploadedByThumper Talk1383421503.534565.jpg


The '07 head is on the top/left, the '12 head is on the bottom/right

Edited by mjruopp

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