kz650 and zr750 engine compatibility?

I have a 1992 750 Zephyr (straight four) that I have torn apart in my garage. Long story short, the last guy to rebuild it pinched a piston ring and ruined the cylinder and piston.

So my question is, is it possible to use the cylinders and pistons from a kz650 but keep the rest of my zr750? (meaning, of course, that it would be a 650) Or would I be better off buying a used zr750 cylinder and just spend loads of money for new pistons and rings?

As far as I know, the kz650's bore x stroke is 62x54 and my zephyr's is 66x54. Another issue is that the zr750 proves to be a lot more rare (at least locally) than a kz650. I'm looking for any input on this: Has it been done? Can it be done? Tips, advice, helpful links?

I am new here but so far it has proven to be an awesome resource.

Thanks all!

Not sure about using the cylinders from the 650, but the 750 sleeves are likely larger O.D. than the 650's meaning that they won't press into the 750 block.

DoubleDub wrote: Not sure about using the cylinders from the 650, but the 750 sleeves are likely larger O.D. than the 650's meaning that they won't press into the 750 block.

Hmm...good point.

What about from a 2000 zr750f?

This one has the same bore and stroke and visually it looks to be the same-Then again I don't really know, hence, looking for some knowledge here.

Throw a GPz 750 engine in it!

All 750 fours use a HyVo style cam chain while 650's (up till 81) use a roller cam chain.

If you use 81+ 650 cylinder block, then the 650 pistons and block are a bolt on.
Otherwise it would be better to find any 750 cylinder block and pistons, and there are tons of them around.

It is plausible that the OD of the cylinder sleeves are smaller than that of the 750, which may prove problematic fitting a 650 rack to your engine, but steell may well be absolutely correct in that it's a bolt-on.

The ZR7 and ZR750 Zephyr should share internals. Older 750s have different pistons. You may be able to source a complete piston and cylinder sleeve for a ZR7/750 from a breaker at a reasonable cost.

Thanks everybody! Think I have a solution now.

Not very knowledgeable on the later engines but one thing I thought of while reading the post was bore spacing. Could very well be the same but it is something to check out.

Kawickrice wrote: Not very knowledgeable on the later engines but one thing I thought of while reading the post was bore spacing. Could very well be the same but it is something to check out.

It's identical between 650 and 750 fours, even the cranks will interchange as long as you match the appropriate cam chain type.

This subject has been extensively researched over the years, right here on KZR, complete with 8x10 glossy photos (Alice's Restaurant reference for the younguns)