How to choose the spark plug for your 125cc motorcycle?

The 2 types of candle?

There are two types of candles:

- The cold candle: with a shorter insulating nozzle.

- The hot candle: equipped with a longer insulating nozzle.

What type of spark plug to choose for a petrol engine?

Copper, iridium, platinum (and double platinum)? The choice of your spark plug is essential for your petrol engine.

- The candle copper wears the fastest, but offers the best possible conductivity.

- The candles platinum and iridium can last a long time but they do not provide superior performance to copper candles.

CODING OF CANDLES NGK

1 - The first thing to do is to remove the antiparasite fixed to the spark plug by pulling on the suppressor itself and not on the wire, then remove the casings or covers which may prevent access to the spark plug.

2 - Very important : Clean the spark plug well with a brush or a compressed air blower to release any impurities that could fall into the cylinder when you remove the spark plug. Loosen the spark plug one or two turns and start the cleaning operation again, to remove the last dirt that could remain stuck.

3 - If the candle is blocked: try to unblock it by forcing it with a spark plug remover more suitable (sometimes a longer lever is enough). If it still resists, run your engine for a few minutes. Expanding the cylinder head may solve the problem. If it is loose, but resists unscrewing a little too much, spray with penetrating.

Terminal cleaning:

First of all remember that cleaning the spark plug is only valid on a spark plug that is going well, or in the case of a greasy spark plug, or just blackened with soot. In the case of a bleached, vitrified or melted spark plug, it must be replaced. Filing a scorched spark plug is useless.

To clean the spark plugs, use a spark plug brush (made of copper so as not to damage the insulators). Important: keep your spark plug turned with the terminals down, so that the debris does not fall into the cylinder.

Terminal spacing adjustment:

With wear and time, the spark plug terminals tend to move apart and the spark (electric arc) is less effective, hence the starting problems.

To adjust the spacing of the terminals, you need a set of wedges. Then you need to read the gap notified on the candle. Then, insert the corresponding shim between the two terminals, and delicately, with a small hammer or ideally a rigid piece of wood, bring the gap back to its correct value, by tapping gently on the thick headed.

4 - Place your cleaned spark plug (or your new spark plug) and screw it in first with your fingers, this is very important. If you do not enter straight it will block, whereas with the spark plug remover you risk "messing up the thread" of the cylinder head. Screw it in this way over several turns, ideally up to the sealing joint.

Tip: put a drop of copper grease, or graphite grease on the thread of the spark plug you are installing. It will be removed more easily during your next spark plug removal operation.

5 - Once the candle is screwed in by hand, finish with the spark plug remover. To ensure ideal tightening, it is best to have a torque wrench and to respect the tightening torque indicated par the constructor. If you don't have one, it is generally advised (once the sealing washer is seated on the cylinder head) to make a 1/2 turn to 3/4 turns blockage. (Depending on whether the spark plug has already been used or not, and therefore whether the seal has already been crushed, or not).

Advice: If you do your maintenance yourself: chain maintenance, oil change, replacement of brake pads, cleaning or replacement of the air filter... Don't hesitate to invest in a torque wrench, vsar the tightening torque is very important!

6 - Before replacing the anti-parasite, take the opportunity to clean it (compressed air, brush, alcohol...). The contact surfaces must be perfectly clean and neat. If it is oxidized, renovate it and test it, or change it.