Topic: CB750K8 Piston Question

[zeffcat]

Hey all. So I'm in the works of a top end rebuild on my 750 K8 and my machinest found the cylinders out of round and suggested a first size overbore. I know that the pistons for the K7/K8 had a slight dome to them and that the top ring was slightly thinner than the K1-K6 pistons so the rings from earlier sets cannot be used in the K7/K8 pistons. However, is it possible to use a set of new pistons and rings for the K1-K6 engines in the K8 engine without causing problems? In my mind it should be fine since the pistons are the same size, its just the top ring slot that is slightly wider on the earlier pistons.

According to CycleX, their pistons which are made in the K1-K6 form are fine to use with the K8 engine. So I would imagine that is also applicable to other earlier piston sets?

[BPellerine]

yes you can use earlier pistons and rings,the 392 pistons had a slight dome so you would have a very small drop in compression,otherwise ok.bill

[zeffcat]

yes you can use earlier pistons and rings,the 392 pistons had a slight dome so you would have a very small drop in compression,otherwise ok.bill

Thanks Bill! That's what I needed to hear.

[Jerry Rxman Griffin aka MuthaF'er]

yes you can use earlier pistons and rings,the 392 pistons had a slight dome so you would have a very small drop in compression,otherwise ok.bill

I have 2 style -392 pistons. Both have 392 cast into them by the pin hole. My original F 392 piston with the full diameter dome and a 392 piston from a K8 engine with a partial dome that does not extend the full diameter. I do not know the ring thicknesses off the top of my head though but could measure if needed.

Either one should work since the head is the same on the early F and the late K.

http://i233.photobucket.com/albums/ee84/RxmanGriff/Honda/P1020789.jpg