Question: I need to change the Piston in my VMAX ABC type engine. How do I remove the Piston without damaging anything?
Answer: First of all you need to remove the cylinder (sleeve). Please see the How to Remove the Cylinder (Sleeve) procedure below.
Note that in nearly 100% of cases, when replacing the piston in an ABC engine, the cylinder should be replaced also. They are generally sold as a set.
Once the cylinder has been removed you can remove the piston complete with connecting rod and wrist pin. There is a trick to this. Please put away your hammer, vice grips, pliers and cutting torch and obtain a carriage bolt that is about 3/16" in diameter and about 3" long. Carriage bolts have a rounded dome like head and are available in pretty much any hardware store.
Securely tighten the prop nut and prop which will serve to pull the crankshaft as far forward in the crankcase as possible. Remove the crankcase backing plate. Lubricate the bottom of the connecting rod where it attaches to the crankshaft pin. Use Pacer After Run Oil or other lubricant. Remembering that there is no cylinder in the crankcase, carefully and slowly rotate the engine 2-3 times by hand and stop with the piston at top dead center (highest point) in the crankcase.
Carefully insert the head end of your carriage bolt into the bottom of the crankcase so that the domed head is centered on the back of the crankshaft and the edge of the domed head is under the bottom edge of the connecting rod. Now use the carriage bolt like a pry bar, to pull the connecting rod back and off the crankshaft pin. There may be some resistance just as it is about to come off. Apply a bit more lubricant and using a bit more pressure on the carriage bolt, rotate the prop about 10-15 degrees and the connecting rod will come off the crankshaft pin.
Flush out any small filings of brass or aluminum using Pacer Degreaser. These small pieces won't be missed by the connecting rod but you don't want them getting into the engine or bearings later on.
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