How to Set Ignition on a Trimmer

Often, owners of gasoline braids are faced with the fact that ignition does not work on their equipment. In most cases, the problem is really in this node. To fix it, you need to adjust the ignition on the trimmer. But at the same time, it is not uncommon that the ignition coil is serviceable, and the breakdown must be sought elsewhere. The ignition system is designed identically on four-stroke and two-stroke internal combustion engines, so the troubleshooting of this unit is performed in a similar way. In addition, the equipment of different brands has almost the same construction of this most important component of the tool, which means that the adjustment process will be identical for the Soyuz or Foreman trimmers, as well as for Huter or samples of other brands.

Ignition on the trimmer. the principle of operation and possible malfunctions

If the owner of the brushcutter wants to set up the ignition system on his own, he should understand the principle of operation of this unit. In an internal combustion engine, it consists of a flywheel and a magneto (coil). In turn, the flywheel includes an impeller that performs the function of cooling the motor and a number of permanent magnets.

How to Set Ignition on a Trimmer

Operating principle

When the flywheel rotates, an electric current is generated in the magneto, creating a spark on the spark plug at the instant when magnets pass under the coil.

Typical malfunctions

Before starting to adjust the trimmer ignition, you need to cut off other probable causes of breakage and make sure that the problem is really in this node. To do this, it is necessary to carry out a series of actions in the following sequence:

  • inspect the ignition coil housing for damage and defects;
  • make sure that all nodes and elements that conduct current, there are no pollution;
  • check the integrity and insulation of the wiring, contacts, fastening strength, the presence of rust at the joints;
  • inspect the candle cap, as it is regularly torn off from the high-voltage wire, and they try to restore it manually, and any unreliable connection reduces the power of the electric arc of the candle;
  • check the candle, because the quality of modern gasoline very quickly disables this part, but there is another possible problem. the candle is wet;
  • make sure the circuit breaker is working.

Eliminating all possible malfunctions, you can proceed to adjust the ignition of the coil.

When adjustment is needed

It is necessary to adjust the ignition system so that the fuel ignites in the combustion chamber at the right time.

Important! When the piston compresses the fuel and almost reaches a dead point from above, a spark arises in the candle. Further, when it passes the maximum upper point, the fuel ignites, as a result of the explosion, energy is generated and directs the piston down.

If the flywheel is shifted on the shaft relative to its original position, the fuel ignites faster than the piston overcomes top dead center. As a result of this, the piston moves backward, and the crankshaft rotates in the opposite direction. It is possible to determine the early ignition of a fuel by a broken launch cord, a broken starter assembly, or other breakdowns..

Sometimes ignition is late. The piston compresses the non-flammable fuel, and then goes down, and only then a spark forms. As a result, the engine either does not work, or its power decreases, and the speed rises much more slowly.

How to Set Ignition on a Trimmer

Typically, a flywheel with magnets is installed in an ideal position, precisely coordinated with the piston, and is carefully fixed to avoid bias. This suggests that incorrect installation of the part is impossible. But if the flywheel shift is a confirmed fact, then it is a malfunction or an accident. Thus, no ignition timing required, since problems with early or late ignition of fuel are very rare.

Important! Adjusting the ignition system is very simple. There is no need to calculate the ignition timing. The maximum that needs to be done is to correctly set the gap between the flywheel and the coil.

Magneto Diagnostics

Magneto is a key component in engine ignition systems. This is a core coil that is surrounded by a primary and then a secondary winding. If this part is faulty, there is no spark on the spark plug, and the fuel does not ignite.

Video: How to Set Ignition on a Trimmer


First way

You can check the performance of magneto using a tester. To do this, you must perform this sequence of actions.

  1. Correctly configure the tester: use the resistance measurement function and set 200 Ohms to take measurements of the primary winding.
  2. Direct the first electrode of the measuring device to the magneto “mass”, and the second to the output contact. If the primary winding is serviceable, the indicators should be from 0.4 to 2 ohms.
  3. Set the tester switch to 20 Com to diagnose the secondary winding. Then direct the first probe into the cap of the candle, and the second. to the "mass". If everything is in order, the indicators will vary from 4 to 6 Kom, depending on the trimmer model, whether it be the Patriot 547, Husquarna 128 r or a different brand of equipment. If the circuit is broken, an infinity value will appear on the tester screen. And if a short circuit occurs, the display will show zero.

Second way

If you can’t use the tester, there is another way to conduct a test. It is important not to touch the cylinder with the electrode, otherwise the coil will be damaged.

  1. It is necessary to remove the cap from the spark plug. Do not unscrew the candle, as this will allow to keep the compression.
  2. Then you need to pick up the nail with the hat removed and firmly insert it into the cap.
  3. Next, the cap with the nail should be firmly tied to the cylinder with a dielectric. In this case, the electrode should be at a distance of 5.5-7 mm from the cylinder body, but not touch the mass.
  4. Then the starter needs to perform an imitation of starting the engine with the ignition button on. In this case, it is necessary to carefully monitor whether a spark appears, and try to determine its color.

Important! A strong spark of white color or with a blue tint testifies in favor of the serviceability of magneto. If it is weak, as well as orange or yellow, the magneto is damaged.

How to Set Ignition on a Trimmer

There is one important point that must be considered when diagnosing: unheated magneto in any state can form a powerful spark. However if it is faulty, then, having warmed up, it stops creating current, and the trimmer will not start. Later, after cooling down, the coil returns to the operating level again, the tiller turns on and for some time runs at idle or under load until the magneto temperature rises again. In this case, the part must be replaced with a new one.

On a note! In some situations, the problem with heating does not occur through the fault of the coil, but because of the spark plug. This means that both parts must be checked.

Ignition Adjustment Procedure

Setting up the ignition system is simple and identical on different trimmers, be it Stihl FS55, Alco BC 4125 or another petrol scythe. First you need to remove the casing from the engine, after having unscrewed the fastening fixing it. This disassembly step may differ on different lawn mowing models (described below). Next, you need to partially unscrew the fastener fixing the magneto with a screwdriver and turn the flywheel so that the magnets are in the upper part.

How to Set Ignition on a Trimmer

How to Set Ignition on a Trimmer

How to Set Ignition on a Trimmer

How to Set Ignition on a Trimmer

To make the optimum clearance between the coil and magneto, you must use a special template. Buying it for a single use is impractical, therefore, as an alternative, you can use a business card or a small pocket calendar, as well as A4 paper sheet folded in four. Also, a strip cut from a plastic bottle or other improvised materials having the required thickness is suitable. The optimum distance is usually indicated in the user manual. The selected item must be placed between the magnets and the coil.

How to Set Ignition on a Trimmer

Then the coil will be attracted to the flywheel by a magnetic field. While holding the magneto in this position, you need to tighten the fixture fixing it, and then pull out the business card. After that, you need to scroll the flywheel several times to make sure that it does not touch the coil at all. The process is over. ignition on the lawn mowing is set. In more detail, the process of adjusting the trim ignition system can be studied on the Internet, where there are many videos dedicated to this topic.

Features of adjustment on different models of trimmers

The ignition system is arranged in a similar way on the technology of various brands, so the process of its adjustment will look the same. The differences, if any, are insignificant. Basically they related to disassembling equipment. For example, removing the casing from the engine on different trimmers is performed with some differences. So, on Patriot devices, you first need to unscrew the bolts and disconnect the air filter housing with a slotted screwdriver. After that, the plastic cover will be very easy to remove. A detailed diagram and trimmer device for a particular model is usually shown in the tool manual.

So, you can do the ignition for a gas trimmer with your own hands. This process is simple if you know the correct procedure. But first you need to exclude the possible malfunctions of other components and parts, for example, spark plugs or magnetos, which can be the reason for the lack of starting the lawn mowing engine. However, when analyzing equipment of different brands, one must take into account the likely differences in design, which are described in detail in the user manual.

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