Removing Stuck Pistons from Two-Cycle Headless Cylinders


| May/June 2001



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Before starting to remove a stuck piston from a cast iron antique headless cylinder, it is important to understand that antique cast iron is not cast steel. Much of it when broken is quite black as compared with modern so-called cast iron, which is typically light gray in color. A good way to determine if that rusty cast iron antique toy is genuine or a modern reproduction someone buried in a manure pile to make it appear old is to file a small area. If it turns up gray don't pay an antique price for it, as it is probably a modern reproduction.

Antique cast iron is much like a ginger snap cookie in that it breaks quite easily, particularly if the stresses on it are not reasonably distributed over the entire casting. This explains the problem of welding cracked cast iron unless it is heated uniformly and cooled under controlled conditions. It is far better for an amateur to repair a cracked water jacket with an epoxy compound than risk further cracking, or worse, wrecking the cylinder by welding or brazing without proper heating and cooling.

The following are the successful methods I have used to remove badly stuck pistons from headless cylinders. There are other possible approaches, but having unfortunately learned the hard way I now stick to the techniques that have succeeded for me without destroying anything.

There is one technique I have always wanted to try but not having an atomic power plant with its endless supply of boiling water I doubt many will be able to take advantage of it. It seems that some success has been obtained by boiling the cylinder in the cooling water of the power plant for 24+ hours and the story goes the piston just fell right out. I wonder???

The easy way to move the piston in a headless cylinder is to fill (leaving no air pocket) the area above the piston with oil. Plug any ports. Adapt a grease gun fitting to a bushing which is screwed into a spark plug hole. A few squirts of grease from the grease gun will generally move the piston with a minimum of stress on the cylinder and piston. This presumes of course that the cylinder walls below the piston skirt have been cleaned of any rust buildup and lubricated with one of the penetrating oils such as WD-40 or equivalent. Unless there is a space between the piston and the cylinder wall, I have had little success with any of the penetrating oils succeeding in breaking the rust seal until the piston has moved a few thousandths. It is prudent to dig out as much rust as possible between the piston skirt and the cylinder wall as there is a normal gap of a few thousandths. (More than a few thousandths in a badly-worn engine)