Topic: CB750/4 K4 Yoshimura 812 piston rings

[Steve Campbell]

Hello all.
I'm doing a minor top end rebuild (valve grind, hone, new rings) and I am needing to source a new set of rings. Bike has a Yoshimura 812 kit so has been bored to 64mm. Anyone know where I can get these rings? I've tried eBay but no luck. Thanks for any leads.

[PeWe]

Are the pistons really OK?
Ring grooves not worn making rings moving up-down in grooves.

My old Action Fours 65mm pistons have a little bit too much ring play after ca 35-40.000 km.

Your choice might be new 65mm pistons like forged JE if engine has more mods like ported head, cam.

It is a pity that 64.5 mm pistons (823cc) are no longer available.
RC had.

Unless CBX1000 pistons can be used. Cruzinimage has stock size 64.5mm kit,  $220US. 2 spare pistons

[Davez134]

I believe rings from the CB350 twin can be used as they are 64mm stock size. I'm not 100% sure though. I've only dealt with 836cc kits on my bikes.

[slikwilli420]

Try Hastings rings. They have stuff for all kinds of obscure pistons.