Pull out all spark plugs, pulling only on the plugs, not on the wires. It is possible to use special pliers to pull (e.g. HAZET 1849). In this case, the plug must be held only by the metal sleeve.
If possible, blow candle niches with compressed air.
Unscrew the spark plugs with a special spark plug wrench and check the appearance of the spark plugs. Based on experience, conclusions can be drawn from this about the operating conditions of the engine.
There are the following rules. Electrodes and insulator:
- Medium gray - the correct adjustment of the carburetor and the correct operation of the candles.
- Black - enriched mixture.
- Light gray - lean mixture.
- Greased - Interruptions in the operation of the corresponding candle or poor sealing of the piston rings.
Clean the spark plugs with a brass brush or sandblaster.
Examine the insulators of the candles for leakage currents. The currents appear as thin, chaotic traces on the outer surface. If it is not possible to completely remove traces of leakage currents, replace the corresponding spark plug.
If necessary, grind the middle electrode with a rectangular file and remove carbon deposits.
Check the distance between the electrodes using a flat feeler gauge. The reference value is 0.8 mm.
To set the distance between the contacts, bend the mass electrode. A simple, practical tool is available for this, otherwise knock on the ground electrode from the side. When bending, rest a small screwdriver on the edge of the spark plug thread. In no case on the central electrode, as otherwise it may be damaged.
Clean the threads on the spark plugs and in the cylinder head.
Screw the spark plugs into the cylinder head by hand as far as they will go.
Attention: Do not put candles with a warp at the stage.
Tighten spark plugs to 20 Nm.
Attention: If a torque wrench is not available. then new spark plugs with a flat o-ring» (R) rotate further by 90° (1/4 turn). Candles with a conical o-ring (IN) rotate by 15°, the same way. as well as used candles from flat.» sealing ring.
If the spark plugs are tightened tightly, the threads in the cylinder head can be torn off or damaged when turning out. In this case, the threads can be repaired using special repair kits.
Put tips on candles.
Check the tightness of their fit and wires by rocking back and forth.