ZR550 cylinders on a GPZ550 1981

Hi,
unfortunally i have on cylinder 1 a lack of compression. Today i pulled the head. Cylinder 1 has scratches. My question is , if the cylinder bank of a Zephyr 550 will fit the GPZ550 head an bottom end?

Thanks David

I don't know if the cylinder blocks interchange, but is the scratched cylinder unrepairable?

The ZR and GPz base and head gaskets are interchangeable, but the later block has bigger fins and a more squared off look.

Whether you compression problem was a scored barrel or something else is remains to be seen.

ZR pistons are slightly lower compression than the GPz items, but you can use either. Check your installed ring gaps and piston to cylinder clearance with feeler guages as a minimum if you are swapping blocks and pistons.

Ok thanks. They might be repairable but it's way cheaper to get good zr550 barrels over here in Germany than buy new pistons and rings and let the barrels hone.
I pull the barrels now and take some pics.

I think any of the KZ550 cylinder blocks should fit your Gpz. Are any of those available?

Here, in the States, it is very cheap to get a used KZ550 motor. Then you would swap over the pistons, head, and oil pan (for the oil cooler).

ZR550 parts are hard to come by here.

Seems like if you are going through the trouble of swapping the block, you might want the ZR head so you can fit the bigger series of carbs (TK26cv/27cv or the ZR's CV30 carbs). Of course, only if you are looking for power. The TK22's will be much easier to tune if you don't need the extra power. Keep the Gpz pistons for the compression. For reference, the ZR cams are the same as the 81-83 Gpz, minus the tach gear.

This is how the barrels look like. The ZR550 barrels are mostly in a better shape with less miles that's why. So the 81 GPZ head with the ZR550 barrels and TK22 would make what power?
I am looking on that bike for more low and power and torque than top speed. For that I have my GPZ900R

accubond wrote: So the 81 GPZ head with the ZR550 barrels and TK22 would make what power?

If the barrels are the same, and you use the Gpz pistons, then it should be the same power as the Gpz motor. If you use the ZR pistons, it will be somewhere between a Gpz and a plain Kz550. The plain KZ550 had a little more low end pull, but did not have nearly as much top end.