How to properly adjust the ignition on the trimmer

The first way

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

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

Second way

If you cannot use the tester, there is another way to test. In this case, it is important not to touch the cylinder with the electrode, otherwise the coil will be damaged..

  • Remove the spark plug cap. You should not unscrew the plug, as this will preserve the compression..
  • Then you need to pick up the nail with the removed cap and insert it tightly into the cap.
  • Next, the cap with the nail should be securely 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.
  • Then, using the starter, you need to simulate starting the engine with the ignition button turned on. In this case, you need to carefully monitor whether a spark appears, and try to determine its color..

Important! A strong spark of white or blue tinge indicates that the magneto is in good working order. If it is weak, or orange or yellow, the magneto is damaged..

adjust, ignition, trimmer

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

On a note! In a number of situations, the problem with heating is not due to the fault of the coil, but due to the spark plug. This means that both parts must be checked..

Operating principle

As the flywheel spins, an electric current is generated in the magneto, creating a spark on the spark plug as the magnets pass under the coil..

Features of adjustment on different models of trimmers

The ignition system works in a similar way on different brands of technology, so the adjustment process will look the same. Differences, if any, are insignificant. They are mainly related to the disassembly of equipment. For example, removing the cover from the engine on different trimmers is done 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, it will be very easy to remove the plastic cover. A detailed diagram and device of a trimmer of a particular model are usually shown in the instruction manual of the tool..

So, you can do the ignition adjustment for a gasoline trimmer with your own hands. This process is not difficult if you know the correct procedure. But first you need to exclude possible malfunctions of other components and parts, for example, spark plugs or magneto, which may be the reason for the lack of engine start of the lawn mowers. However, disassembling equipment of different brands, you need to take into account the likely differences in design, which are described in detail in the user manual..

Magneto diagnostics

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

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 dead center at the top, a spark is generated in the spark plug. Further, when it passes the maximum high point, the fuel ignites, as a result of the explosion, energy is generated and directs the piston down.

If the flywheel is displaced on the shaft from its original position, the fuel ignites faster than the piston crosses top dead center. As a result, the piston moves backward and the crankshaft rotates in the opposite direction. An early ignition of fuel can be determined by a broken starter cord, a broken starter assembly or other breakdowns..

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

Usually, the flywheel with magnets is set in an ideal position, precisely coordinated with the operation of the piston, and is carefully locked to avoid misalignment. This allows us to assert that the incorrect installation of the part is impossible. But if the flywheel offset is a confirmed fact, then it is a malfunction or an accident. Thus, setting the ignition timing is not required, since problems with early or late ignition of the fuel are very rare..

Important! It is very easy to adjust the ignition system. There is no need to calculate the ignition timing. The most that needs to be done is to correctly set the clearance between the flywheel and the coil..

Ignition adjustment procedure

Setting up the ignition system is simple and identical on different trimmer models, be it a Stihl FS55, AL-KO BC 4125 or another lawn mower. First you need to remove the casing from the engine, having previously unscrewed the fasteners that fix it. This disassembly step may differ from model to lawnmower (described below). Next, you need to partially unscrew the fasteners that fix the magneto with a screwdriver, and turn the flywheel so that the magnets are in the upper part.

In order to create an optimal gap between the coil and the magneto, a special template must be used. It is impractical to buy it for a single use, therefore, as an alternative, you can use a business card or a small pocket calendar, as well as an A4 paper sheet folded in four. A strip cut from a plastic bottle or other available materials that have the required thickness is also suitable. The optimal distance is usually indicated in the user manual. The selected item must be placed between the magnets and the coil.

The coil will then be attracted to the flywheel by the magnetic field. While holding the magneto in this position, you need to tighten the fasteners that fix it, and then pull out the business card. After that, you need to turn the flywheel several times to make sure that it does not touch the coil at all. The process is over – the lawnmower’s ignition is on. You can learn more about the process of adjusting the trimmer ignition system on the Internet, where many videos on this topic are available..

Typical malfunctions

Before you start adjusting the ignition of the trimmer, you need to cut off other probable causes of breakdown and make sure that the problem is really in this unit. To do this, it is necessary to carry out a number of actions in the following sequence:

  • inspect the ignition coil housing for damage and defects;
  • make sure that there is no contamination on all nodes and elements that conduct current;
  • check the integrity and insulation of the wiring, contacts, fastening strength, the presence of rust at the joints;
  • inspect the candle cap, as it regularly comes off 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, since the quality of modern gasoline very quickly destroys this part, but there is another possible problem – the candle is wet;
  • make sure the circuit breaker is working.

Having excluded all possible malfunctions, you can proceed to adjusting the ignition of the coil.

No spark on the tiller – reasons and solutions

Features of the

In the low voltage winding, a current is induced in the process of changing the magnetic voltage in the core, caused by the rotation of the magnet (turned to this end of the U-shaped core by either the north or south pole, that is, the magnetic flux changes direction) with closed contacts. This change lasts for a time of the order of ten milliseconds (ms).

At the end of this process we have an inductor with a current of several Amperes, closed by the contacts of the breaker. At a certain moment, the contacts open, and a cycle of harmonic oscillations begins in the circuit formed by the inductance of the low voltage winding and the capacitance mentioned above (plus the parasitic capacitance of the windings, especially the capacitance of the HV winding, transformed into the LV winding).

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The oscillation period is about 1 ms.

The contacts of the breaker do not break through due to the fact that the voltage on the capacitor rises slowly (in fact, this is one of the goals of installing a capacitor in the magneto), and they manage to disperse far from each other by the time the decaying sinusoidal voltage reaches its full value (after a quarter of the period after the contacts open) , that is, the moment of maximum voltage.

But usually this moment is not achieved: the spark gap in the spark plug breaks through, and the capacitor energy passes into the spark discharge zone in the combustible mixture of the engine cylinder, during the oscillatory process in the capacitors and inductances of the magneto structure, lasting about 1 ms. Then the contacts close, and the next cycle begins, the process of current growth with a change in the magnetic field, etc..

Condenser malfunctions:

  • open leads
  • breakdown
  • poor contacts of the capacitor body with ground and an insulated conductor with the breaker terminal

Best way to set the gap on any ignition coil, magneto, armature, part 1

These malfunctions are determined on the ignition checker (PPZ) or using a warning lamp.

A control lamp connected in series with a capacitor and connected to a 220 V alternating current network does not light when the capacitor is in good working order, but after the capacitor is disconnected from the network during shunting, a spark appears. If there is a break in the capacitor, the lamp does not light up, and the capacitor does not charge.

When a capacitor breaks down, the lamp burns. Replace the damaged capacitor.

No spark

This is one of the typical malfunctions of the tiller ignition system. The most common reasons for this are spark plug deposits or spark plug breakage. In this case, unscrew the candle and carefully inspect its side and central electrodes..

If the spark plug is covered with carbon deposits formed as a result of flooding the part with a fuel mixture, then cleaning the spark plug alone will not be enough – you will need to check the pipes of the tiller’s fuel system for leaks.

Examples of cases of highly contaminated spark plugs are clearly visible in the photo..

If the spark is gone, then in any case, you will need to thoroughly clean the candle. To do this, it is best to heat it over a gas burner, then scrape off the dried fuel from the surface..

After cleaning the part, put the tip on its upper part and bring it to the tiller motor housing. The candle must be held so that its electrode is about 1 millimeter from the engine body.

At the same time, try to start the tiller motor with the second hand..

If the candle is completely serviceable, then a spark is formed in its lower part, which will jump out and hit the motor housing. If this does not happen, then you need to inspect the distance between the side and central electrodes..

A blade should be placed between them, and if it fits snugly between the two electrodes, then the gap is of the optimal size. If the blade dangles, then you need to knock with any hard object on the back of the central electrode.

As a result, it will shift, after which you need to try to start the tiller engine again..

Magneto, or in search of a spark

how to find the spark with the EFCO magneto petrol trimmer

Magneto is a magnetoelectric alternator that creates electrical discharges between spark plug electrodes to ignite the working mixture in the cylinders of internal combustion engines.

Magneto works on the principle of electromagnetic induction.

The essence of induction is as follows: when a magnetic field is crossed by a closed conductor, an electric current arises in this conductor. When an electric current passes through a conductor, a magnetic field is generated around that conductor..

Magnetic field – the space around a magnet in which the magnetic force of the mowing line (or magnetic flux) travels. these mowing lines are located denser between the poles of the magnet.

An alternating current can be excited in a conductor by rapidly reversing the direction of the crossing magnetic flux, for example by rotating a magnet around a wire coil. This is the principle behind the work of a magneto with a rotating magnet..

When the magnet rotates, the magnetic flux passing through the rod changes in magnitude and direction; as a result, an electric current arises in the winding, first in one direction, and then in the other.

The capacitor serves to improve the operation of the magneto. In the presence of a capacitor, a strong spark is formed, without it, a weak spark.

The capacitor is connected in parallel with the contacts of the breaker in order to reduce the sparking that occurs when the primary current is interrupted at the contacts of the breaker.

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How magneto works?

When the magnet rotates, it excites current and the primary winding, short-circuited by the contacts of the breaker.

When the current in the primary circuit reaches its maximum, the breaker contacts open. Because of this, the primary current is instantly interrupted. The magnetic field that was created by the primary current also disappears.

This sudden change in the magnetic field excites a high voltage current in the secondary circuit, capable of punching the gap between the electrodes of the corresponding candle..

Further rotation of the magneto rotor causes the formation of a new spark, etc..

How to check the technical condition of a magneto?

In the process of daily operation, the performance of the magneto can be checked as follows: connect the high-voltage wire to the high-voltage terminal and keep the other end of the wire at a distance of 5-7 mm from the magneto body, sharply turn the rotor in the direction of rotation. At the same time, a correctly assembled and adjusted magneto with a sharp turn of the rotor should give a spark that ensures the breakdown of the above gap. If there is no spark or it is weak, check the integrity of the magneto and wire insulation.


Probable cause

Interruption of sparking
Oily or burnt contacts
Clean the contacts with chamois soaked in pure gasoline or file the contacts if they are burnt

The gap between the contacts is out of alignment
Adjust clearance

The cushion of the breaker lever is worn out
Replace the breaker lever with a new one.

The outline is out of alignment
Adjust clearance

Capacitor broken
Replace capacitor

Magneto doesn’t spark
Opening of the primary or secondary circuit of the transformer
Replace transformer

Short circuit to ground primary circuit
Eliminate the short circuit

Breakdown of high-voltage wire insulation
Replace wire

Magneto gives a faint spark
Capacitor broken
Replace capacitor

Disassembly and side magneto.

– remove the magneto from the engine; – clean it of dust and oil and disassemble it in the following order: – use a socket wrench to unscrew the fastening nut of the ignition timing machine, remove it and remove the key from the groove; – move aside the latch, remove the breaker cover; – unscrew the four screws securing the cover, remove the cover; – remove the magneto rotor from the housing;

– unscrew the transformer mounting studs, remove the transformer from the housing.

Reassemble the magneto in the reverse order..

To replace the breaker contacts, proceed as follows:

– move aside the latch, remove the breaker cover; – unscrew the screw securing the connecting conductor; – unscrew the screw securing the breaker plate to the magneto cover, remove the breaker plate; – unscrew the screw securing the breaker spring; – remove the lock washer from the axle of the lever cushion, remove the lever with cushion assembly from the axle;

– unscrew the screw securing the contact rack, remove the contact rack from the axis.

Reassemble the breaker in the reverse order..

Luck with searching! But it is easier to change the magneto for a new one or give it to the service department (if there is a guarantee, this can be done free of charge).

Repair Magneto MB-1: a detailed description of the process

Heating should be carried out slowly, until the entire volume is completely warmed up – usually in a thermostat it takes about 30 … 40 minutes. The coils may not withstand this temperature, so they must be removed before heating. If in the process of cutting the epoxy it cools down, the heating must be repeated

How to Set/Adjust the Air Gap on Small Engines Armature Magneto Coil

Typical wear and tear of magneto and their elimination

  • demagnetizing the rotor
  • shorting of windings
  • capacitor failure
  • breakdown of parts of current-collecting and distribution devices
  • breaker, accelerator or advance clutch malfunctions
  • wear of ball bearings and seats
  • damage to individual parts
  • violation of contacts in the primary circuit
  • demagnetization
  • damage to the thread
  • shaft deflection
  • wear of bearing seats
  • magnetic flux
  • generated by the transformer
  • overheat
  • concussions and blows

The seats for ball bearings are restored by knurling followed by grinding. The deflection of the rotor shaft is eliminated by straightening.

The rotor magnetization is determined by the MD-4 magnetometer. The rotor is magnetized on a special device NA-5VIM with direct current.