Removing a Stuck Piston from a 2-Stroke Engine

One successful method for removing a stuck piston from a 2-stroke engine

| January/February 1979

  • Removing a stuck piston

  • Removing a stuck piston

Recently a reader was faced with the problem of removing a stuck piston from a 2-stroke engine, realizing that the good old grease/oil pressure method would not work because of porting. Can't remember how he solved the problem, for trying to drive out the stuck piston with a narrow rod through the spark plug hole in the non-removable head is most hazardous for the future of the stuck piston.

As a recipient of a very ancient Vaughan 4 HP drag saw, I was faced with the same problem of removing a stuck piston. On this 2-stroke engine even blocking the intake and exhaust openings would not help because fuel-oil mixture enters the cylinders through large ports in the piston wall! Prolonged soaking of kerosene and penetrating oil did not seem to help the stuck piston any either. But there had to be a way of removing that stuck piston, short of using dynamite.

The piston was finally removed from the 2-stroke engine successfully as follows: (See diagram.)

Two pieces of 1/4" thick cold-rolled steel about 1-1/4" and 2-1/2" long were drilled in three places to allow bolting to the bronze connecting rod in lieu of the end cap and also to hold a long threaded bolt 3/8" diameter and 5" long. The crankshaft throw was turned directly down. The cylinder was placed over the crankcase mouth in its usual position and the long bolt protruded through the large rear hole in the crankcase. Two 1/2" diameter steel rods were placed across the end of the crankcase, one on either side of the long bolt and a large washer, then a nut was placed on the bolt and drawn up snug with a crescent wrench. Threads of the bolt were oiled liberally, more penetrating oil was sprayed into the cylinder and an old gasoline blow torch was directed at the underside of the cylinder base. When the cylinder began to feel quite warm, then the work began of turning the nut to draw the piston out. Due to a small boss inside the crankcase, the piston could be drawn out only about 2-1/2" at the first pass. However, large nuts set on edge were used as temporary shims between the cylinder flange and crankcase and work continued until only 1" of piston was still in the cylinder. The piston was subsequently fairly easily removed by hand. Two successive 3/8" bolts were needed to do the job for one was stripped due to the force exerted. The piston resisted removal every inch of the way.

There is undoubtedly a better, easiest way to remove stuck 2-stroke pistons but this method does work- safely.

Later model Vaughan 2 stroke drag-saw engines do not have removable cylinders. As 1 recently discovered to my chagrin, to remove stuck pistons upon such engines, the crankshaft must be completely removed.


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