Dear all, I've this old piston that I hope has a bit of remaining life - if I can only replace the rings! The problem is getting the old ones out. It was running on Castrol R and the top two rings are well and truly stuck; I can't get even a dentist's tooth pick in at the ring gap (probably lack of gap was the problem). Are there solvents for Castrol R? Can you use a small cutting disc to dismember the ring?
Use heat to expand the piston more than the rings - nothing fancy to start with, just boil it in water with some washing-up liquid for a while and see what happens. Avoid industrial cleaner -it can eat the alloy. Bob.
My avatar shows the late Len Rich in 1970 with the bike I now have - a 1958 Ariel VH
Heat is best. Get it pretty hot especially the top and prise an end out. You may end up breaking it into a few pieces but try to have it up a bit before each section breaks, to allow a small screwdriver or such to get under what remains. Nev
The heavy burnt varnish is dissolved by a paint remover of the chlorinated kind.....dont use a caustic alkali,it will eat the alloy.......If the methyl chloride paint remover isnt available any more,try some spray carburretor cleaner,or maybe brake cleaner.
I've had success removing stuck rings by soaking the piston in acetone - just leave it in soak and eventually the ring expands a little under it's own elasticity, once it begins to move I speed the process by exercising it. Not had to break one yet.
Thanks for your advice, gents. I've had the piston inverted and soaking the rings in acetone for 3 weeks but no luck on easing them. Heating and cooling was no help either so I'm using a small cutter disc in a small 12v hand held drill device to cut out a piece of the upper ring. I'll let you know how I get on. (It's tricky.) Nev, re the "big cut in the oil ring groove" that's just the shadow of the land above. My apologies for the late reply but very now and again I get chucked off this site and forget both my name and password! It always causes me grief and delay. Regards from MikeN.
I've had another look at that piston. Wire wheel buff the ring area and heat it from the crown. Aluminium expands a fair bit more than iron. I've never had one you couldn't get the rings out of. If you slip with the cutter and go into the aluminium, it's the end of the piston . The lands need to be an accurate fit and good parallel surfaces.Nev