Removing Stuck Pistons from Two-Cycle Headless Cylinders
(Page 3 of 6)
May/June 2001
Richard A. Day Jr
When withdrawing the piston, make note of the angular position
of the piston ring gap, as the rings in old-time two cycle engines
are normally pinned so they don't rotate and get hung up in the
ports. Some pistons may have a ring near the bottom of the piston
and this ring never travels far enough up to trap in one of the
ports. Such rings are not typically pinned.
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Also check that the piston baffle was adjacent to the inlet
port. This precaution can save a lot of grief when reassembling the
engine. On occasion I have found a previous owner must have
disassembled the engine and reversed the baffle so it was adjacent
to the exhaust port. This could explain why the engine no longer
was in use, as it probably didn't run very well if it ran at
all. When removing the rings, keep in mind there is a top and
bottom to each ring and turning a pinned ring over can make it
impossible to correctly install the ring without it hanging up in
one of the ports.
The set up for pressing the piston IN is quite different
from a hydraulic push OUT when the ports are covered. In this set
up we first create a lead mold to distribute the stress over the
entire cylinder head.
1. Plug any openings in the cylinder head area where they may be
covered with lead. Otherwise you will have a problem withdrawing
the lead mold and cleaning out the lead in the openings. Wooden
plugs work well and don't need to protrude as pipe plugs, etc.
may. Set the cylinder out in the sun for six to eight hours to
remove any chill in the iron. This slow even method of heating is
much less stressful than trying to heat it with a torch. Both the
inner jacket walls and the outer jacket wall need to reach about
the same temperature, so aim it so the sunlight can penetrate into
the bottom of the stuck piston. Rotate it from time to time to try
and spread the heating as much as possible all over the cylinder.
If one has an oven, raise the temperature to approximately 150
degrees over a period of several hours. Keep in mind we are not
trying to prepare this cylinder for welding, so don't get the
temperature so high that the lead will not solidify and we
don't want to risk the cylinder to cracking due to rapid
uncontrolled cooling from a very high
temperature.
We are just trying to remove the CHILL so the
lead will follow the contours of the head and not stress the
cylinder with a high heat shock.
2. Make a circular dam out of sheet metal approximately 3'
high.
3. Make it big enough in diameter to permit lowering the
cylinder, head end, into the middle of the dam with enough
clearance to make it easy to pour in the molten lead.
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