Topic: High top pistons in a CB750K1.

[aussie cb750 k1]

I have just bought a '71 CB750K1 & am at the start of restoring it to it's former glory.I am down to the stage of checking the piston clearances & removing the pistons but something dosen't add up.
The cylinder bore is 64.7mm & the pistons are not flat as in the Clymer manual.They have a large dome on them with extremely large valve cutaways.The rings show 'T' & 75 on each side of the ring gap.
Anyone help with this question......what have I got in this engine that makes it go like stink!

[MCRider]

64mm is 811cc. 65mm is 836cc, two popular kits. Hi dome = high compression ratio, exactly what = unknown.

Your measurement is likely a bit sloppy and its an 836 kit.

[aussie cb750 k1]

BY the way....it does not have piston pin circlips- only white nylon end caps on the pin which float up & down with the piston.What sort of kit is this??

[MCRider]

BY the way....it does not have piston pin circlips- only white nylon end caps on the pin which float up & down with the piston.What sort of kit is this??

Those are known as buttons. RC Engineering used them, probably others. I'm not so sure they are (as) popular now.

I think they were thought to give the piston some stability in the bores, OCICBW