On the engine mod. 4062, candles of the A14DVR type are installed, on engines mod. 402 and 4021 - type A14VR
1. Examine the candle. If cracks are visible on the spark plug insulator, the threads or electrodes of the spark plug are damaged, it must be replaced.
Pay attention to the soot that covers the lower part of the candle.
If light brown soot covers the spark plug evenly with a thin layer, it can be left uncleaned, as it does not affect the operation of the ignition system.
If there is no carbon deposits at all, this indicates that the engine is running on a lean mixture or with an increased ignition timing.
If the spark plug is covered with a matte black soot that can be easily rubbed off, this indicates that the engine is running on a rich mixture.
If the soot is shiny black, this indicates that an excessive amount of oil has entered the engine cylinder.
Black deposits must be cleaned with a sandblaster and then blown out with compressed air. You can clean the carbon deposits from a candle with a stiff hair brush, after dipping the candle in gasoline for 20–30 minutes.
It is not recommended to clean the soot with sharp metal objects: they will leave scratches on the candle, which will accelerate the process of soot formation.
2. After cleaning the carbon deposits, check the gap between the spark plug electrodes. Check the gap only with a round probe, since when checking with a flat one, the depth of the recess on the side electrode, which is formed during the operation of the candle, will not be taken into account.
The gap must be between 0.7–0.85mm for motor mod. 4062 and 0.8–0.95 mm for motors mod. 402 and 4021.
If the gap does not fit within the specified limits, adjust it by bending the side electrode 1.
Bending the central electrode is prohibited - this will lead to cracks in the insulator and failure of the candle.
Replacing candles
1. At the engine mod. 4062 remove tip 1 of spark plug with seal 2 without disconnecting high-voltage wire from tip 1.
Use key 3 to turn out the old candle.
Then wrap a new one. Do not tighten the spark plug very strongly, the tightening torque of the spark plug is 31–38 Nm (3.1–3.8 kgf m).
Put tip 1 on the spark plug and install seal 2 so that the lower edge of the seal is put on the flanging of the hole in the cylinder head cover.
2. For engines mod. 402 and 4021, remove the tip of 1 spark plug without disconnecting the high-voltage wire from it.
Unscrew the old candle with a wrench, wrap the new one. Plug tightening torque 30–40 Nm (3.0–4.0 kgf m).
Put tip 1 on the candle.