This operation can be performed either with the engine removed from the vehicle or without removing it.
With the cylinder head removed, thoroughly clean all traces of carbon deposits from the combustion chambers and valve bores, as well as from the valve stems and guides, using a wire brush and scraper. To pre-clean the combustion chambers, you can use a piece of an old piston ring.
Wash the combustion chambers and valve holes with gasoline, scrape off all 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 tops of the cylinder bores. If the pistons are in the cylinders, care must be taken to prevent pieces of carbon from getting into the cylinder and scratching 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 cloth in the other two cylinders or cover them with paper using tape. Coolant passages and connecting rod bores should also be sealed with tape to prevent carbon particles from entering the cooling or lubrication system.
Using a scraper, carefully scrape away any carbon deposits from the piston head, being careful not to scratch the aluminum. Clean off any carbon deposits from the portion of the cylinder wall surrounding the piston.
Caution: Use a vacuum cleaner to remove any carbon deposits that have entered the engine cylinders.
To prevent carbon deposits, polish the piston crown. Remove the rags or tape from the other two cylinders and turn the crankshaft so that the two pistons that were in the lower position move to the upper position. Repeat the operation described above.
[The article is borrowed from the website: hyundaibook.ru]