2. Candles should be replaced at the intervals specified in the section "Ongoing maintenance" at the beginning of this guide. A thorough inspection of the spark plugs can tell a lot about the condition of the engine.
3. If the heat cone of the spark plug is clean and white, without a dark coating, then this is a sign of too lean mixture or too hot candle (a hot plug slowly transfers heat away from the electrode, a cold plug quickly).
4. If the top and heat cone of the spark plug is coated with a dense black coating, then this is a sign of too rich a mixture. If the candles are covered with a black oily coating, then this indicates that the engine is very worn out, and the mixture is most likely too rich.
5. If the heat cone has a light brown to greyish coating, the mixture is correct and the engine is most likely in good condition.
6. The size of the spark gap is of great importance. If it is too large or too small, the efficiency of the candle will be greatly reduced. Refer to the Specifications at the beginning of this chapter for the correct spark gap.
7. The size of the spark gap is adjusted by bending the side electrode. In no case do not try to bend the central electrode, because. this may damage the insulator.
8. Recommended candle types are listed in Specifications. Candles should have a conical body and be installed without washers. Because the head is made of light alloy, be careful not to overtighten the spark plugs. It is best to use a torque wrench with a long head from a spark plug wrench to tighten them. Check that the spark plug bodies and the walls of the spark plug holes are clean. Check that the ignition wires are connected in the correct order (see b/fig. 4.5).
9. Ignition wires do not require routine maintenance. It is enough to keep them clean and wipe them regularly. When removing spark plugs for cleaning or replacement, disconnect the wires one at a time so as not to confuse them. Before connecting the wires, clean their ends from traces of corrosion and carefully wipe the leads under the wires on the cover of the distributor.
10. High voltage wires degrade slowly over time, so it is recommended to replace them regardless of condition during normal engine maintenance. It is better not to throw away old wires, but to leave them in the car just in case.