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Hi all, I am trying to source a piston for my kz750 ltd H1, but can only get the superseded version which has slightly larger valve recesses, (not the later type with the large valve recesses, gpz etc),does anyone know if the superseded version will be ok?, it’s just I don’t fancy having one piston different to the other three. I have already messed up by buying four chineese pistons of eBay without realising. Would appreciate if anyone can give me info on this.

Not sure if it's too late to answer, but no, as long as the valve reliefs are large enough for your valves, it doesn't matter that it is different than the rest.

Curtiss

That is assuming the rest of the piston is the same. The weights of the pistons should be the same, or very close.

Any difference in piston crown or deck height may affect compression chamber volume, and therefore compression. Meaning unbalanced power between cylinders. Buy four of the same.

I should have given more information I guess. Yes, it is best to run 4 identical pistons. It was also not mentioned what "slightly larger valve reliefs" means exactly. If you must use that odd piston, as I said earlier, if the piston is identical - and I mean absolutely identical - other than the valve reliefs, the difference in compression on the running engine would make little difference, depending on what slightly larger means. If the reliefs are not deeper, but have a slightly different eyelash cut for a larger valve, the effect on squeeze will be minimal for a street engine. All depends on what you expect from the engine. Something to putt around on is one thing, race engine is another. It's not ideal, but if you must, it is possible.

Having said all that, and considering the knowledge required, you should just buy 4 identical pistons.