I found a broken top ring in my M33. Both the top and bottom of this ring and the top of the ring below appear to be worn. The ring grooves look okay, but the gap between the top two rings and their grooves is over tolerance (the bottom ring is fine).
Can anybody tell me the thickness these two top rings are supposed to be? I'm hoping to work out whether I need a set of rings or a new piston and rebore.
I think the compression rings are ⅛" x 0.1" but I can't be sure. You should be able to measure the ones you have.
You can buy individual rings from Cox & Turner Engineering. https://www.coxandturner.co.uk/piston-rings/ (https://www.coxandturner.co.uk/piston-rings/)
:) :) :) :)
A long time ago, I was given to believe that Broken top rings where often the sign of piston slap, hence suggestive of bore wear and probable rebore required.
So my thoughts---Get the bore measured and see where it goes from there, because without that info you have no base line to work from.
My own stand point is;- if its just within limits= rebore it. If its well within go down the pistons/rings route.
Mike 8) 8) 8)
Quote from: Mike Farmer on 24 Mar, 2023, 11:50
:) :) :) :)
A long time ago, I was given to believe that Broken top rings where often the sign of piston slap, hence suggestive of bore wear and probable rebore required.
So my thoughts---Get the bore measured and see where it goes from there, because without that info you have no base line to work from.
My own stand point is;- if its just within limits= rebore it. If its well within go down the pistons/rings route.
Mike 8) 8) 8)
Fair point, but if it's the piston grooves that are worn and not the rings, it doesn't matter how nice a fit the piston is in the bore. As it happens, I decided earlier today to take the barrel and piston to an engine shop to be measured. But that'll be next week, when I pick up the other bits they are working on for me. I'll show 'em the rings, too.
According to the old Hepolite catalogues the B33/M33 2 top rings are 3/32 inch thick and clearance in the grooves should be 0.0015 inch - 0.0035 inch.
Quote from: JulianS on 24 Mar, 2023, 22:46
According to the old Hepolite catalogues the B33/M33 2 top rings are 3/32 inch thick and clearance in the grooves should be 0.0015 inch - 0.0035 inch.
Thanks Julian. This probably means a rebore, then. Oh well.
I took the barrel and piston to the engine shop, as I said I would. As I feared, he said if the rings are worn (on their top and bottom faces) then so are the piston grooves. He said it's down to over-fueling; a rich mixture. Okay, a rebore it is. Thanks to all.
:) :) :) :)
Thanks for the update.
Mike 8) 8) 8) 8)