This operation can be performed both with the engine removed from the vehicle and without removing it.
With the cylinder head removed, carefully clean all traces of carbon deposits from the combustion chambers and valve bores, as well as from the valve stems and guides, with a wire brush and scraper. To pre-clean the combustion chambers, you can use a piece of the old piston ring.
Flush the combustion chambers and valve bores with gasoline, scrape off any foreign material from the surface of the cylinder head with the side of a steel ruler or similar tool, being careful not to damage the surface.
Clean the pistons and the top of the cylinder bores. If the pistons are in the cylinders, care must be taken so that pieces of soot do not get into the cylinder and scratch the walls, piston or rings. To do this, turn the crankshaft so that the two pistons are at the top of the cylinders. Place a clean rag in the other two cylinders or cover them with paper and tape. The coolant passages and connecting rod holes should also be sealed with adhesive tape to prevent carbon particles from entering the cooling or lubrication system.
Using a scraper, carefully scrape off carbon deposits from the piston head, being careful not to scratch the aluminum. Clean off carbon deposits from the part of the cylinder wall surrounding the piston.
Caution: Use a vacuum cleaner to remove carbon deposits that have entered the engine cylinders.
Polish the piston crown to prevent carbon deposits. Remove the rags or tape from the other two cylinders and rotate the crankshaft so that the two pistons that were in the down position move up. Repeat the operation above.