2. To remove the valves, it is necessary to compress the springs so that the cotters can be pulled out of the groove in the upper part of the valve stem.
3. Position the spring compressor so that the fork at the end of the lever rests on the valve spring retainer and the clamp screw rests against the surface of the valve head.
4. Tighten the clamp so as to compress the springs and relieve the pressure of the spring plate on the crackers. If the plate gets stuck, hold the valve head and lightly tap the clamp with a hammer.
5. Pull out 2 crackers, release the spring and remove the compressor. Remove the plate and spring and remove the valve.
b. As you remove the valves, place them in order so that they are not mixed up during installation. You can take a piece of cardboard, make 8 holes in it and insert valves into them.
7. Remembering that the cylinder head is made of light alloy, clean it from carbon deposits with a blunt scraper or a rotary wire brush. Valve stems and guide bushings must also be cleaned. Flush the combustion chambers and all openings with kerosene and clean the outer surface of the head using a blunt scraper.
8. If the engine is on the machine, clean the pistons and the top of the cylinders. If the pistons are still in the cylinder block, make sure that the carbon deposits being removed do not get into the cylinders, as it can scratch cylinder walls and damage pistons and piston rings. To prevent this from happening, you must first turn the crankshaft so that the 2 pistons are in the upper position. Cover the remaining 2 cylinders with rags or cover them with paper. You should also cover the water jacket passages to prevent dirt from getting into the cooling system and damaging the water pump.
9. Apply some lubricant to the space between the pistons and the cylinder walls and use a blunt scraper to scrape away carbon deposits from the piston heads, being careful not to scratch the aluminum. Clean carbon deposits from the adjacent edges of the cylinders as well. Remove contaminated lubricant, being careful not to push it into the cylinders. To prevent carbon buildup, the piston crowns can be treated with metal polishing paste, but be sure to remove all traces of paste afterwards. Pull the rags out of the remaining two cylinders and turn the crankshaft so that the pistons in them are in the upper position. Cover the cleaned cylinders with rags and repeat the procedure.
10. Inspect the valve heads for pitting and burning (especially the exhaust valve heads). At the same time, inspect the valve seats. With minor pitting of valves and seats, the defects can be removed during valve grinding.
11. If the valve seats are severely pitted, they will have to be recut and new valves installed (made by a specialist). In practice, it is extremely unlikely that the saddles will be badly worn. Valves usually require replacement. New valves must be ground into the seats.
12. The valves are grinded in as follows. Apply some coarse carborundum paste to the valve seat and place a lapping tool on the valve. Using semi-rotational movements, rub the valve head against the seat, lifting the valve from time to time and redistributing the lapping paste. Once dull matte streaks appear on the seat and valve head, wipe off the paste and repeat the entire process with fine carborundum paste. Grinding in will be much easier if you install a weak spring under the valve head. Once smooth matte light gray stripes appear on the seat and valve head, the grinding can be considered complete. Carefully wipe off all traces of paste from the valves and seats, making sure that it does not get into the holes or valve guides. Wipe the valves and seats with a rag soaked in kerosene, and then with a clean rag and blow out the valves, guides and all holes with compressed air.
13. Inspect the valve springs - damaged springs must be replaced. Check the free length of the springs (relatively new springs). Springs that are not long enough must be replaced. Springs are subject to fatigue deformation and it is recommended to replace them even if they appear to be in good order.
14. Check the cylinder head for deformation, either by placing it on a glass sheet or using a ruler and thickness gauges. If the sealing surface of the head is slightly bent, it should be taken to a specialist for processing.
15. On engines 1.6 and 1.8, each time the head is overhauled, the sealing ring between it and the thermostat housing should be replaced. Replacing the O-ring is extremely difficult if the head is in place on the engine (see chapter 2).
16. If it is necessary to replace the pressure control valve located in the cylinder head, then access to it is through the ring plug covering the end of the valve. The old valve should be broken, its remains pulled out and threaded (M10) in the valve seat so that it can be removed using a suitable bolt. After this, you can drive the new valve into place along with the plug. Given the certain complexity of this operation, it is recommended to entrust it to a specialist.
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