CB360 GS750 69.5mm Pistons

So I bought the four 69.5mm Pistons off eBay for the GS750. I was hoping these would work for a max displacement CB360 build.

I am hoping these will be usable since they call them "high compression"

Thoughts!?

don't know for sure but try taking the head/barrels off (which you'll be doing anyway), measure the crown height of the CB360 pistons from the gudgeon pin and do the same to the GS pistons, subtract the difference and then see how far the valves come down into the combustion chamber, see if theres any space left......
maybe also check the angle the valves come down into the piston cutouts to make sure they're not going to be an ínterference fit
the above statement makes sense in my head when I think it but when I see it written down...not so sure, hope it might be of some help

stock gs750 pistons are 65mm. don't know that anyone made a 4.5mm big bore kit so have to guess those are high compression gs850 pistons and in that case i would definitely clay it up to find the true valve to piston clearance because stock gs850 pistons are already high compression as a cb360 big bore piston. chances are they will have clearance but will have too much dome cc to be within a reasonable CR. neat find there i doubt you'll find any more. don't forget to calculate the static compression ratio precisely as well before deciding whether to run them

Pretty sure I recall crazyPJ using GS850 pistons in his 360's. Maybe PM him and see if he knows.

Yeah, GS850 is the normal swap. I bought a set from a '79 for mine. If you can't confirm the 750 by Saturday, I can measure mine up when I get back in town.


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They won't arrive until mid-Feb. the seller is away. The size was intriguing and that maybe I can get some more compression without shaving the barrels.