Ignition tuning on trimmer

On gasoline trimmers, both two-stroke internal combustion engines (ICE) and four-stroke engines are used. But the ignition system in them is no different from each other, so the repair and tuning of this ignition system will be the same for different types of internal combustion engines.

How does the ignition system on the trimmer

The two-stroke engine ignition system consists of 2 elements: a flywheel and a coil (magneto). The figure below shows how they look.

On the flywheel is the impeller, which works as a fan to cool the engine. Also on one side of the flywheel are permanent magnets, the figure shows the arrow.

During the rotation of the flywheel in the coil produces an electric current,which serves to spark a spark plug. A spark appears at the moment when the magnets are directly under the magneto.

Why do I need to adjust the ignition

In some cases, when the engine does not start, an ignition adjustment will be required. Of course, you first need to check the serviceability of the spark plug and high-voltage cable with a cap.

Adjusting the ignition on a two-stroke engine is necessary in order to ensure timely ignition of the fuel in the engine's combustion chamber.. Below is a diagram from which you can understand the principle of operation of the internal combustion engine.

The spark in the candle should appear at the moment of compression of the fuel by the piston, when it does not reach the top dead center (TDC) just a little. When the piston passes TDC, the fuel mixture ignites, causing the piston to fall down under the action of the energy of the explosion.

Therefore, if for any reason (mainly due to the displacement of the flywheel on the shaft relative to its original position), the fuel ignites before the piston passes the TDC, then it goes back and the crankshaft rotates in the opposite direction.Such a movement can damage the starter assembly, tear the launch cord, etc. In this case happens early ignition of fuel.

May also be late ignition on the trimmer: the piston after compression of the fuel, which has not ignited, goes down, and at this moment a spark appears. In this case, the engine will either not start, or it will significantly lose power and it will be bad to gain momentum.

But such problems with early or late ignition on two-stroke ICEs are quite rare, since the flywheel with magnets is already installed in the correct position, which is perfectly synchronized with the movement of the piston. In addition, the flywheel is fixed to the shaft with a key and nut. Therefore, incorrect installation of the part is excluded.

Basically, the ignition control is to set the correct gap between the magneto and the flywheel.

How to check the health of magneto

Magneto is the main component in the engine ignition system and is a coil with primary and secondary windings located around the core.. Often, due to a malfunctioning magneto, the spark on the spark plug disappears, and the ignition of the fuel does not occur.To check the coil, you will need to use a tester, and perform the following steps.

1. On the tester, going into the resistance measurement mode, you need to set 200 Ohms. This method will check the primary winding.
2. Connect one electrode of the tester to the “mass” of the coil, and the second to the contact coming out of the magneto. Normally, the resistance should be between 0.4 and 2 ohms.
3. To check the secondary winding, you will need to set the instrument switch to 20 com. Further, one probe of the device is inserted into the cap of the candle, and the second is connected to the “mass”. Normally, resistance indicators should be in the range of 4-6 lump and higher (depending on the model).

When the circuit is open, the device will show infinity, and when it is closed, it will show 0 (zero).

If you do not have a tester, then you can use the following method, taking great care so that the electrode does not touch the cylinder, otherwise the coil will blow.

1. Remove the cap from the candle. Candle twist does not need to save compression.
2. It is necessary to insert a nail without a cap into the cap. The nail must be of such diameter that it is well kept in the cap.
3. Tie the cap with a nail to the cylinder using a dielectric, so that the gap between the electrode and the cylinder body is in the range of 5.5 to 7 mm (but in no case does not touch the “mass”).
4. Using the starter, perform an engine start imitation several times. The ignition button must be on.
5. Observe whether a spark appears and what color it has.

Normally, the spark should be strong, white in color or have a bluish tint. If the spark is weak and its color is orange or yellow, this indicates a faulty magneto.

You should also take into account the fact that sometimes a magneto in a cold state can produce a good spark. But after heating due to internal faults ceases to produce current. As soon as the coil cools, the trimmer starts up again and works for a while until the magneto warms up again. This coil must be replaced.

Sometimes a spark plug can cause a similar problem with heating, even if the coil is healthy, so you need to check both parts.

Ignition Adjustment Algorithm

Trimmer lighting is fairly easy to adjust.

1. Remove the cover from the engine by unscrewing all the bolts holding it.For example, on the Patriot benzokosa (Patriot) PT 2540, to remove the cover, you need to unscrew the air filter housing, and remove it from the latches with a flat screwdriver. After that, the plastic case can be easily removed.
   

   

   

2. Using a screwdriver, loosen the 2 bolts (do not completely unscrew) holding the magneto.
3. Turn the flywheel so that the magnets are on top.
   

4. Further, to correctly set the best gap between the flywheel and the coil, you can use the usual business card or pocket calendar. If you do not have one or the other, you can use A4 sheet of paper to adjust the ignition by folding it 2 times (in the end, you will have 4 sheets of thickness). This thickness will be enough to get the optimum clearance and adjust the ignition. Insert a business card or paper between the coil and the magnets.
   
5. The magnetic field will attract the coil to the flywheel. Holding the magneto with your fingers in this position, tighten the bolts holding it.
6. Remove the card. After that, the ignition on the trimmer will be adjusted.