Engine Decarboning: Cylinder Removal and Cleaning
WARNING: The author of this page is not a professional or certified aircraft engine mechanic. The information contained herein constitutes a description of the writer's experience only and should not be construed or interpreted by the reader as instructions or guidance for the successful completion of any repair or maintenance procedure. Use of any information contained herein is at the user's own risk. This information has not been reviewed, evaluated, or approved by the manufacturer of this engine.
 |
After removing the cylinder heads carefully lift the cylinder itself just high enough to slip two wood spacers or the rubber padded handles of a pair of pliers under the piston skirt. If using wood, make sure it's clean and free of any debris that could fall into the case. If the piston is at the bottom of its stroke, rotate the crankshaft and raise the cylinder and piston together until the bottom of the piston is about an inch above the crankcase. Then place the spacers and rotate the crankshaft to lower the piston and cylinder together until the piston contacts them. This will support the piston, keep it centered, and keep it from flopping against the cylinder bolts when it comes free from the cylinder. Then raise the cylinder carefully as you support the piston from underneath. Gentle wiggling of the cylinder and the piston may be necessary if things get a little stuck. Don't force anything and be sure to keep the piston centered and straight up and down as it comes out of the bore of the cylinder. Mark each cylinder for reassembly in the same position.
|
With the cylinder off the engine the old head gasket can be removed. If it's stuck to the cylinder by carbon deposits you can break it loose by slipping a razor blade under the edge of the gasket being careful not to scratch or gouge the sealing surface of the cylinder. Be sure to mark and note the location of the rubber pad at the rear of the PTO cylinder. That one's easily knocked off as you work on the cylinders. Pitch all used gaskets no matter how good they look (the cylinder base gaskets will be particularly tempting. This ain't no snowmobile we're working on here..... |
 |
 |
There may be a ridge of carbon around the top of the cylinder. The heavier material is easily removed with the sharpened dowel. Cleanup of the gasket sealing surface and any deposits remaining at the very top of the cylinder wall can be accomplished by wiping with a rag soaked with kerosene and gentle scraping with the edge of a credit card
|
Similarly, any deposits in and around the exhaust port are loosened with the wooden scraper then cleaned up with a scotchbrite pad and/or rag and kerosene. Pay attention to the ridge around the edge of the port but be careful not to scratch the machined gasket sealing surface. When it's clean, rinse the cylinder with clean solvent. Be careful not to clean away any location marks, including your cylinder position letter or number, when you're finishing up. Wash with warm water and dish detergent to remove any oily residue from the cooling fins, then blow dry and wipe all exposed surfaces of the steel liner with a soft rag lightly oiled with two-cycle oil. Make sure the gasket sealing surfaces are clean, oil-free, and dry. If the cylinder will sit around on your bench for any time while you work on other parts it'd be a good idea to wrap it in a plastic bag or clean rag; a clean oiled surface like the cylinder liner is a dirt magnet. |
 |