I have a 06 zx14 with 10k on it and I broke a valve. Can I change one OEM piston or do i have too change all the pistons?

Say the cylinder wall finish is not damaged:
1. Do not sand it.
2. Do not bottle brush it.
3. It's ready to be reentered into service.

Say the head's dome is dinged up:
1. Gotta see a photo to address this one.
2. Sand the dug in spots with a dremel sanding head, not a carbide bit.
3. The more you clean up the dome, the more compression lost.

Say the rod can be pulled by removing the sump cover only.
1. Obviously the head has to come off and you bypass the case split.
2. Okay, the case needs to be split, then you still replace those rod inserts.
3. Lets assume the piston stopped at TDC, the damage to the dome occurred, we take no chance reusing the inserts because the crush at the dome transfers also to the squish at the inserts, even though they still look good.
4. We change the piston, new wrist pin, new cir-clips, new rod inserts, new rings and reinstall.
5. The case is split so now it's easier to remove the one rod only.
6. Leave the other pistons in place.

Say the cylinder is damaged:
1. We now pull the top case off and send it to Millennium for cylinder work.
2. We also send the head to repair the head damage.
3. We install all new valves to that one head chamber.
4. We install the one new piston (with related parts) only.

http://mt-llc.com/