Trim Plug Gap

Trimmer ignition coil malfunctions and repair How to repair the trimmer ignition coil: check the operation, remove and disassemble, replace the breaker and magneto contacts. What coil malfunctions can be, and how to avoid them.

No sparking

If the magneto does not spark at all, the main cause is an open circuit in one of the transformer circuits (primary or secondary). To fix the petrol cutter, replace the defective part. If the primary circuit is shorted to ground, it can also cause no spark. You need to fix it to fix the problem.

If there is no multimeter, you can check the coil in another way.

To diagnose, you need to take the following steps:

  • Open the cover that covers the cylinder;
  • Remove the cap of the high-voltage wire from the candle without unscrewing the part itself to maintain compression;
  • Tightly place a nail without a cap in the cap, it will simulate the central electrode of the candle;
  • Use a dielectric material to tie the cap with a nail to the cylinder so that the gap between the simulator of the spark plug electrode and the mass ranges from 5.5 to 7 mm (the exact distance for a particular model is recommended to be found in the user manual), but the part does not come into contact with the mass;
  • Using the starter to reproduce the engine start several times, holding the ignition button in the on position;
  • If a spark appears, you need to consider what color it is.
Trim Plug Gap

A strong white or bluish spark is normal, and a faint flash of orange or yellow indicates coil failure.

Often, a cold magneto creates a powerful spark, but when heated, due to a defect in internal components, it does not conduct current. After the coil of the brushcutter has cooled, it starts up again and mows the grass with a fishing line or knife until the magneto is heated. This is abnormal behavior and the coil must be changed.

Disassembling magneto

Disassembling the magneto is very simple. First you need to remove this device from the engine and clean it, removing oil particles and dirt.. Further, since the ignition timing machine is securely fastened, you need to unscrew the nut, and then remove the part and pull the key out of the groove. The cover is fixed with four screws; to remove it, you need to unscrew and remove the fasteners. Then you need to pull out the magneto rotor from the case, unscrew the pins holding the transformer and get it out. And to collect the magneto, you need to follow the steps described above in reverse order.

Functional check

Before starting to diagnose magneto, you need to make sure that the problem is actually in this node. To do this, you need to check the entire chain and make sure that there are no other reasons for the breakage of the trimmer.

  1. First, you should carefully inspect the coil for cracks and other external defects on the case. Next, you need to examine all the elements and nodes that conduct current, and make sure that they are clean.
  2. The next step is to inspect high-voltage wires. They must be in good working order and securely attached to the contacts, free from rust and with intact insulation.
  3. The next step is to check the plug cap. As a result of careless actions, the user often tears it off the high-voltage wire, and then improvises and creates a homemade mount. You need to understand that any poor-quality connection in this place significantly reduces the power of the electric arc of the candle.
  4. Then you should make sure that the candle itself is in good working order. If you fill the brushcutter with poor quality gasoline, the service life of this part is significantly reduced. In addition, it may be flooded or have a large carbon deposit that interferes with operation. Sometimes the candle even sticks and doesn’t twist off.
  5. Next, you need to inspect the circuit breaker. On trimmers and chainsaws made in China, it often breaks.

After completing all these steps and excluding the listed nodes from the list of possible causes of failure, you should proceed to checking the coil. This can be done in several ways.

Method 1

The first way to check the ignition coil involves the use of special equipment (stand). At home, it is not available, you can find it only in service centers.

Insufficient sparking

The weak spark on the magneto is caused by a damaged capacitor. To eliminate the damage, it is necessary to replace the failed part.

Why do I need ignition adjustment

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

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

The spark in the plug should appear at the moment the fuel is compressed by the piston, when it does not even reach the top dead center (TDC). When the piston passes TDC, the fuel mixture ignites, as a result of which the piston goes down under the action of the explosion energy.

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

There may also be a late ignition on the trim: the piston, after the compression of the fuel that 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 difficult to gain speed.

But such problems with early or late ignition on two-stroke internal combustion engines 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 secured to the shaft with a key and nut. Therefore, incorrect installation of the part is excluded.

How to check the health of a magneto

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

  1. On the tester, after switching to the resistance measurement mode, you need to set 200 ohms. In this way, the primary winding will be checked.
  2. Connect one electrode of the tester to coil ground and the other 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 need to set the device switch to 20 kΩ. Further, one probe of the device is inserted into the candle cap, and the second is connected to the “mass”. Normally, resistance indicators should be in the range of 4-6 kΩ and above (depending on the model).

If you do not have a tester, then you can use the following method, being very careful so that the electrode does not touch the cylinder, otherwise the coil will burn out.

  1. Remove the cap from the candle. The candle does not need to be twisted to maintain compression.
  2. It is necessary to insert a nail without a cap into the cap. The nail should be of such a diameter that it adheres well to the cap.
  3. Tie the nail cap to the cylinder using a dielectric so that the gap between the electrode and the cylinder body is between 5.5 and 7 mm (but never touches the “ground”).
  4. Using the starter, simulate engine start several times. The ignition button must be on.
  5. Observe if a spark appears and what color it has.

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

You should also consider the fact that sometimes cold magneto can give a good spark. But after heating, due to internal faults, it ceases to produce current. As soon as the coil cools down, the trimmer starts again and runs for a while until the magneto warms up again. This coil must be replaced.

How the trimmer ignition system works

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

The flywheel has an impeller that acts as a fan to cool the engine. Also on one side of the flywheel are permanent magnets, shown by an arrow in the figure.

When the flywheel rotates, an electric current is generated in the coil, which serves to produce a spark on the spark plug. A spark appears when the magnets are directly below the magneto.

Trimmer ignition setting

Gasoline trimmers use both two-stroke internal combustion engines (ICEs) and four-stroke ones. But the ignition system in them is no different from each other, therefore, the repair and adjustment of this fuel ignition system will be the same for different types of internal combustion engines.

Ignition adjustment algorithm

The trimmer ignition is fairly easy to adjust.

  1. Remove the engine cover from the engine by unscrewing all bolts holding it. For example, on a Patriot (Patriot) PT 2540 petrol cutter, to remove the casing, you will 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.
  • Using a screwdriver, unscrew the 2 screws (not completely unscrewed) holding the magneto.
  • Turn the handwheel so the magnets are at the top.
  • Further, in order to correctly set the best clearance between the flywheel and the coil, you can use a regular business card or pocket calendar. If you do not have either one or the other at hand, then to set up the ignition, you can use a sheet of A4 paper by folding it 2 times (as a result, you will get a thickness of 4 sheets). This thickness will be sufficient to obtain an optimal clearance and adjust the ignition. Insert a business card or paper between the spool and the magnets.
  • The magnetic field will pull the coil towards the flywheel. While holding the magneto in this position with your fingers, tighten the bolts that hold it.
  • Remove the business card. The trimmer ignition will then be adjusted.

The device and principle of operation of the chainsaw ignition system

The standard ignition system for a carburetor engine consists of:

  • Magneto;
  • Spark plug;
  • An electric cable connecting them to each other;
  • Engine shutdown keys.
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Chainsaw ignition scheme Ural

Magneto is a type of alternator that supplies power to spark plugs. It consists of a stationary winding of an inductor and a permanent magnet attached to a flywheel that rotates with the crankshaft of a gasoline engine. The moving magnetic field creates an electromotive force in the low-voltage winding, which is converted by the transformer into a voltage with a potential sufficient to generate a spark.

In contact magneto, the first terminal of the high-voltage winding is connected to the spark plug, and the second through a mechanical switch to ground. At a certain moment, a special structural element divides the contacts, which leads to a sharp increase in the voltage in the network and a spark slip in the interelectrode space of the candle.

The ignition circuit of a chainsaw with a contactless magneto is based on the operation of a control coil, which plays the role of a voltage supply regulator. The electronic unit also includes a diode, a capacitor and a thyristor, which transmits current with a voltage of a certain magnitude. When it is opened, the capacitor is intensively discharged, forming a current in the turns of the primary winding, which is inducted into a high voltage, giving a breakdown on the spark plug installed in the cylinder. The electrical network operates in a pulse mode in time with the rotation of the crankshaft and the translational movement of the cylinders.

Ignition adjustment on a chainsaw Ignition timing

The mechanical device and the factory setting of the magneto ensure that the discharge time of the spark plug coincides with the optimal position of the moving piston. For four-stroke gasoline engines, spark breakthrough must occur even before the piston reaches top dead center, this is due to the fact that the process of complete ignition of the air-fuel mixture takes a certain time. The speed of movement of engine parts is comparable to the speed of fuel ignition, so the piston has time to travel a certain distance from the moment the spark breaks through to the moment the burning gases create extremely high pressure.

There is an ignition timing for each engine. It is equal to the rotation of the crank, expressed in degrees, from the moment of breakdown in the interelectrode space of the spark plug until the moment when the piston is at top dead center. This indicator depends on many parameters, including the design features of the engine and the properties of the fuel mixture.

When is the ignition setting required? There are the main symptoms of a system failure:

  • The engine will not start;
  • The motor works, but with noticeable interruptions;
  • There is a decrease in the power of the tool.

In these cases, you should not rush to contact the service center. Try to adjust the ignition yourself first.

The procedure for checking and adjusting the correct operation of the engine

The most vulnerable element of a carburetor engine is the spark plug. It also allows you to judge the probable causes of malfunction of individual units of a gasoline engine. The following procedure is recommended.

  1. Dismantle the spark plug and inspect it. A dry candle with a light brown tint of the electrodes can be considered serviceable.

When installing a new electrical module on the engine, the magneto gap must be adjusted. The optimum distance between the flywheel and the ignition coil is 0.2-0.4 mm for most chainsaws.

Gap between magneto and flywheel

With such a small gap, it will not be possible to use an available measuring tool for direct measurement. In practice, a Husqvarna saw uses a template in the form of a spacer cut from thin and flexible sheet material of the required thickness. It is clamped in the space between the flywheel and the coil during installation, and then pulled out.

In order not to have to resort to adjusting the ignition, operate the tool carefully, avoiding impacts. In particular, this applies to chainsaws with electronic chips in the ignition system, since they are very sensitive to mechanical damage.

How to repair a petrol cutter if the engine does not start.

Before repairing the petrol cutters with your own hands, you first need to identify the malfunction. First you need to check the filters, both fuel and air. If necessary, the air filter can be washed in gasoline or with water and detergents.

After that, the filter is well wrung out and dried. Before installing on the air filter, it is advisable to moisten a couple of drops of oil for 2-stroke engines.
The fuel filter is not washed, only replaced.

Cleaning the mesh in the muffler

The exhaust muffler is equipped with a mesh anti-spark shield. Over time, this screen clogs up, building up soot from burnt oil and reducing engine power output. This problem can be solved by cleaning the mesh with an old toothbrush, compressed air, or a small wire brush.

As you can see, repairing petrol cutters with your own hands is not such a difficult matter and many will be able to fix most of the faults.

Gas cutters design

The trimmer consists of three parts: a gasoline engine, a bar with a shaft inside and a cutting element. The torque is transmitted through the shaft from the motor to the cutting head. In curved bar trimmers, the cable acts as the shaft. The rod itself is attached to the gasoline engine gearbox. There is an engine control on the bar, and a belt can also be attached for convenient use of the trimmer. The cutting element in gas mowers uses a line wound around a trimmer head or a special knife used to trim large weeds.

The main and most complex trimmer unit is the engine. In household and semi-professional brushcutters, two types of engines are used, 2-stroke or 4-stroke. Depending on the type of gasoline engine, its filling and maintenance are different.

  • 2-stroke engines do not have their own lubrication system, therefore they do not run on pure gasoline, but on a mixture of gasoline and oil. The latter, entering the combustion chamber, lubricates the moving components of the engine.
  • 4-stroke engines are lubricated with oil in the crankcase. They run on pure gasoline without impurities.
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Do-it-yourself petrol brush repair and trimmer maintenance can be done without outside help. If you need to replace spare parts for the motor or adjust it, then you need to contact a repair shop.

DIY petrol brush repair: malfunctions and their elimination

One of the basic gardening tools in the garden or in the country is a petrol cutter or trimmer. Gardeners use this tool for mowing grass, weed control, lawn mowing. Like any other tool, the trimmer requires careful maintenance and do-it-yourself routine repairs are required.

First launch at the beginning of the season

In late spring, when the active use of mowers begins, before starting work, you need to make an inspection and check for the performance of your tool. It is imperative to lubricate the rotating parts, inspect and, if necessary, replace the cutting elements (knife or fishing line). Check for fuel mixture in the tank. If you have drained fuel at the end of the previous season, remember to suck fuel into the engine (if the engine has one).

Starting most two-stroke engines is fairly straightforward. Use the procedure outlined in your trimmer’s instructions if it differs from the following:

  1. Move the choke lever to the open position. Position the trimmer on its side with the air filter on top.
  2. Hold or lock the throttle in the on position (the throttle should be held until the engine is warm).
  3. If the device has an on / off switch, move it to the on position (usually indicated by an I rather than an O).
  4. Give a sharp, quick jerk with the starter grip until you hear the engine try to start. This should happen between 1-6 jerks, but no more.
  5. Close throttle halfway and restart starter starting. The engine should start after 2-6 additional jerks. If not, move the throttle lever to full position and pull the starter grip again. Return the lever to half the throttle and pull 3 more times.
  6. After starting the engine, continue to hold the start button down and let it warm up for 10 seconds, then disable the starting system.
  7. When the brushcutter warms up, it should restart with the throttle in the covered position.

You can also use another proven trick. If, before starting, you remove the air filter and pour a couple of drops of the mixture into the carburetor and collect it again, the engine should start.

Checking the glow plug.

On a cold engine, remove the high-voltage wire from the spark plug and unscrew it with a special wrench. This key is provided by the manufacturer so that you can easily repair the petrol brush yourself.

First, visually inspect it for contamination, also check if it is flooded with a fuel mixture. If the candle is dirty, clean it with a needle file or iron brush. If the plug is flooded, it must be dried, and the remaining fuel must be drained from the combustion chamber through the plug hole. Be sure to check the spark plug gap, it should be no more than 0.6 mm.

If cracks are visible on the ceramic part of the candle, be sure to replace the candle.

Trimmer candles

Spark plug tester 42-087 OREGON

Barcode: 5400182927754

Product Description

The 42-087 Spark Plug Tester will allow you to test the spark plug and check for ignition problems before replacing any parts.

Product information

  • Checks the health of your spark plug
  • Analogue to BS 19368 tester
  • Use with a running engine

Spark plug OREGON 77-307-1

Analogs: Champion RCJ6Y; Bosch WSR6F; NGK BPMR7A, Brisk PR15Y.

Fits Stihl and Husqvarna, Echo 3050, 3500, 350WES Universal spark plug 77-307-1 fits most chainsaws and trimmers.

A type: Mini

Heat number: 15

Distance between electrodes: 0.6 mm;

Case dimensions: М14х1.25;

Thread length: 9mm;

Key: 19 mm.

Suitable for Stihl and Husqvarna chainsaws and brushcutters.

The OREGON spark plug is specially designed for use in chainsaws, petrol trimmers and lawn mowers. They operate very reliably at partial load and also at maximum speed, which is one of the main requirements. The special design ensures long service life and high vibration resistance.

The spark plug for OREGON 77-307-1 2-stroke engines is manufactured in accordance with the requirements of ISO / TS 16949: 2002.

  • The spark plug is designed for chain saws, brush cutters and mowers.
  • Provides easy engine starting even in cold weather
  • Complete combustion, clean exhaust
  • Longer service life
  • High European quality
  • Excellent vibration resistance

Analogs of the OREGON 77-307-1 candle:

BOSCH: 0242240576, 0242240846, 0242245533, WSR5F, WSR6F, WSR6F200, 0 242 235 651, 0 242 245 533, 0 242 540 572, WKA 200 T 6, WKA 200 TR 6, WSR 5 F, WSR 6 F, WSR 7 F, WRS5F, WSR7F, 0 241 245 555, 0 242 240 576, WS 5 F;

BRISK: PR15Y, PR17YC, PR 15 Y;

CHAMPION: RCJ6Y, RCJ 6Y, RCJ 6 Y, RCJ 7 Y, RCJ7Y, 859, A425306-0400, A425306-0401, A425309-0210, A425309-0211, A425309-0301, KCJ7Y, 859S, CJ6Y, CJ7Y;

KAWASAKI: E920702107, 92070-2107, E 92070-2107, 9207 02107, E 9207 02107;

NGK: 4626, 6703, 6761, BPMR 7A, 309, 4345, BPMR 7 A, BPMR6A, BPMR6A10, BPMR6AVP1, BPMR7AVP1, BPMR7Y, 3201, 4921, 7221, 7321, 7472, BPM7, BPM7A, BPM7Y;

SOLO: 2300730, 23 00 389;

YAMAHA: 90793-20098;

STIHL: 1110 400 7005, 1110 400 7005 A, 1113 400 7000;


PAL: PR 15 Y, PR15Y;

DENSO: W22MPRU, 067700-3350;

HONDA: 98073-57944;

ACDelco: CS42S;