How to check the ignition coil of a chainsaw?
There are several effective ways to check a factory ignition coil. The first one is visual. To do this, the operator must carefully remove the magneto from the saw structure, having previously disconnected all contacts connected to it. After that, you need to inspect the item.
Most often, its malfunctions consist in:
- damage to standard insulation, initially caused by gradual or sudden overheating, increased vibration, as well as voltage surges in the created electrical network. All this leads to a short circuit in the factory windings of the coil;
- violation of the integrity of standard high-voltage wires. this results in overload and breakage of electrical wires.
In any of these cases, you will need to immediately replace the electronic ignition of the gasoline chain saw.
The second way to check the coil is to test it with a multimeter.
- Connect the device to the positive and parallel negative factory contacts, having previously configured it in the mode of constant measurement of the generated resistance;
- After ringing the built-in coil, you need to look at the device. In household chainsaws from different manufacturers, the resistance values may differ from each other. Typically, the average is around 0.4–2 ohms. If zero resistance is displayed on the multimeter used, then an accidental short circuit has occurred in its standard winding. In few cases, the device can show infinity. then the operator will need to find an open circuit.
In each of these cases, the repair of the factory ignition coil is carried out only through a complete replacement of the part.
Each of the methods allows you to obtain information about the health and stability of the factory ignition system of a gasoline saw. In some models of garden power tools, manufacturers provide for the possibility of replacing only the defective coil. In other cases, the owners of chainsaws are required to replace the entire ignition system.
How to determine the advance angle of the built-in ignition?
The design of the built-in ignition coil ensures coincidence between the factory optimal position of the moving piston and spark plug discharge. During the operation of 4-stroke power units, the spark must jump before the piston returns to the uppermost position. This is due to the fact that such engines take longer to burn fuel. In their factory device, the speed of operation of the internal combustion engine parts is equal to the speed of the planned ignition of the filled fuel. In this regard, the piston manages to pass a certain path from the moment of instantaneous breakthrough of the created spark to the place where the candle is located. until the period for which the burning gases are guaranteed to have time to create extremely high pressure indicators.
During the mass assembly of engines under standard factory conditions, manufacturers do not perform ignition adjustments. Instead, markings are left on the rotating elements that must be aligned during installation.
In order for a gasoline saw to start running stably at idle, the fuel located in the factory cylinder of its power unit must ignite. For this, a standard ignition system is provided in the basic configuration of any branded chain tool. The ability of the internal combustion engine to make the first cold start and steadily gain momentum when the operator presses the gas trigger largely depends on its serviceability. The ignition of a household saw is distinguished by a simple device and a constant operating principle. Having studied their features, it will be easier for the operator to carry out maintenance and self-repair of the unit.
Factory Ignition System Design Features
The ignition system for a domestic or professional chainsaw initially consists of:
- magneto, or factory ignition coil;
- candles with a pre-installed cap;
- electrical high-voltage wiring, pre-connecting the spark plug to the coil;
- keys that instantly turn off the running power unit of the chainsaw.
In the device of a household gasoline tool, magneto is a kind of generator responsible for the continuous generation of alternating current with the subsequent transfer of energy to the built-in candle. The design of the magneto initially consists directly of a standard stationary winding of an inductive coil, as well as a permanently operating magnet pre-installed on the built-in flywheel.
Magneto, provided in the standard built-in ignition device for household and professional gasoline saws, are divided by equipment manufacturers into:
- contact. in the design of these nodes, the first output of the built-in factory high-voltage winding is connected to the spark plugs. In the basic design of the contact magneto, a capacitor is initially provided, which prevents overheating and gradual oxidation of the contacts of the standard breaker;
- non-contact. the principle of operation of units of this type is based on the operation of the built-in control coil of the factory, which, at the same time, plays the role of an element that regulates the supply of voltage. During the regular opening of the thyristor, the standard capacitor begins to actively discharge. As a result, a sufficiently high current is continuously generated in the turns of the high-voltage factory primary winding, which is inducted into the high-voltage voltage. It leads to instantaneous breakdown at the built-in spark plug located in the cylinder of the power unit. The electrical network of the non-contact magneto operates stably in the mode of continuously generated short-term pulses generated in time with each forward movement of the factory cylinder and the corresponding rotation of the engine crankshaft.
Manufacturers of chain garden equipment use different types of factory magneto in the configuration of chainsaws. The main difference between them lies only in the principle of action. At the same time, contact and non-contact magneto have approximately the same working efficiency.
How to set the ignition on a chainsaw?
As in the case of the constant need for self-adjustment of the carburetor, a chainsaw used in a private economy or on a forest shaft must be amenable to timely adjustment of the built-in standard ignition. The essence of this procedure is to install the gap originally provided between the flywheel of the power unit and the standard ignition coil. The size of this gap may initially be different. it all depends on the purpose, as well as the design features of the saw. The average distance is considered to be not less than 0.2 and not more than 0.4 mm. In the event of a violation of the correct gap, the base ignition system will not be able to generate the spark required for timely instantaneous ignition of the filled fuel mixture in time.
In order to initially correctly adjust the appropriate clearance between the flywheel and the ignition coil on the chainsaw, its owner will need a special plate template. However, buying it for a one-time use is not always profitable. In some cases, the template can be replaced with a homemade one. To make it, the operator will need a plastic smooth bottle, from the side of which a thin strip must be cut. At the same time, there should be no embossing on a homemade template.
The operator can adjust the ignition on the chainsaw directly in the following order:
- First, you need to slightly loosen the plastic bolts designed to fix the standard ignition element;
- Further, the magnets provided on the flywheel will need to be brought to the factory coil;
- Then, a homemade or previously purchased template must be installed between the base high-voltage coil and the built-in engine flywheel. After that, the coil fixing bolts will need to be tightened in the opposite direction;
- Next, the operator must carefully remove the template.
- At the end, you will need to scroll the built-in flywheel. At the same time, you need to make sure that when rotating, the element does not touch the coil and other parts of the chainsaw.
How To Correctly Set Ignition On A Lawn Mower
It does not matter what equipment, and especially the garden one, which works in rather difficult any conditions, asks for maintenance. Even its ordinary and small service significantly increases the resource of this technique, and makes the work itself more ordinary and pleasant. And the motors start up “half-at-a-time”, and work massively and without a rumble and bounce.
Such a small service for his own equipment is provided by its owner himself, without the need to take it to a special service. Using this article as an example, I will tell you about the necessary work that needs to be done on a gasoline lawn mower. With other mowers, our client will have approximately the same.
After the past season and wintering in a cool barn, the mower needs to be cleaned and lubricated. External cleaning was made back in the fall, before storage, at the moment it is necessary to carry out it more painstakingly and prepare the lawn mower for the battle with grass and weeds.
First of all, you need to remove the protective covers from the motor of the petrol lawn mower. This will provide easier access to the main components and facilitate work. We will also be able to inspect the starter device, remove dust, particles of dry grass and other debris from under the casing that interfere with the normal cooling of the engine. And it is not a secret for anyone, the air quality is influenced specifically by the cleanliness of the motor.
The motor cover (in my MTD SP 48 model) is secured with 4 screws (item 1 in the photo). We pass the starter handle through the gap and remove the casing.
Now our company can remove the starter device and gain access to the main engine components. For this purpose, unscrew the 3 screws that strengthen both the starter launcher and the fairing of the flywheel fan.
Carefully clean the starting device of debris and inspect the launcher’s cable. If it is damaged, you will have to change it to a new one by disassembling the launcher itself. There is an option to return a slight “disheveledness” of the cable with the help of a certain elastic glue (rubber, PVA). Those. one that would glue the villi to each other, but the gluing site remained elastic.
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Now let’s take a look at the braking system. (item 3 in the photo). It is designed for a quick stop of the engine when it is turned off. The brake pad is pressed against the engine flywheel, while the ignition wire is shorted to ground.
Appreciated by women, both the shoe and the flywheel are made to beat clean. If necessary, the brake pad is replaced or adjusted. The cable and the spring of the brake mechanism are also cleaned and lubricated. With all this, it is comfortable to use the lubricant in aerosol cans.
Change of oil in the engine crankcase. It must be created according to the annotation for the gas mower, but not less often than once a season, even if you mowed slightly. As the oil oxidizes and its lubricating performance deteriorates.
To drain the old oil, the lawn mower is tilted towards the drain hole (item 1 in the photo), placing a block of wood or something else under the wheels. If you wish to prevent the old oil from flowing into the protective casing, a small groove is cut out of the plastic bottle where the old oil will drain into the substituted container without staining the casing. When there is anything left to do for our client, the oil will drain, the hole is closed and new oil is poured through the oil filler neck to the desired level. Use oil with the viscosity recommended by the manufacturer. Typically 10W40 for 4 stroke engines. It is pointless to use more watery and expensive grades, because the engine does not have an oil pump and lubrication is done with oil mist. And the operation of the lawn mower takes place at positive temperatures. And expensive oils show their characteristics only in extreme situations.
We assemble and install all casings in a reverse order.
The final step of the “technical inspection” is the revision of the knives. On different forums there are mutually exclusive views, sharpening them or not sharpening. I am an adherent of “do not sharpen”. They are appreciated by women, if they have bullying and bends left by the stones that you tried to mow, then they need to be removed. But sharpening the edge to a razor sharpness does not make any sense. And the arguments are as follows. First, for example, the grass trimmer line is generally round. And nothing, perfectly chops the grass. Secondly, the grass itself is better when it is not cut, but pinched off. The cut end of the grass usually turns yellow and dries up. And pinched off. rapidly overgrows, healing the wound. And also, as far as you did not sharpen the knives, after half an hour of work, they will go into their professionalism in a normal working condition. Those. this will be a metal edge with a rounding of 0.5 mm across. In such a state, they will be working for a very long time. The knife cuts the grass with the force of impact, inertia, and not with sharpness. Therefore, only more noticeable burrs need to be removed from the knife with ratfil or an abrasive bar, this will be enough.
How to set the ignition?
Having removed the fan cowl, we painstakingly clean the fairing and fan blades from debris using a stiff brush with a long bristle. Now let’s move on to the motor nodes.
The ignition system of a lawn mower is arranged as follows. A permanent magnet is integrated into the flywheel of the motor. When it “flies” past the magneto poles (pos. 4.5 in the photo), the magnetic flux closes and an electromotive force is induced in the magneto coil. With the help of an electrical circuit, the myth impulse is shortened in time and a powerful impulse is formed, sufficient for an electronic breakdown of the spark plug gap (item 1)
Specifically, the quality of the spark ensures the ease of starting the mower motor. Therefore, we do such operations.
First, unscrew the spark plug and inspect it. If last season the lawn mower had to do a great job, then it is better to immediately replace it with the newest one, to sell it if the old one still looks decent. The new one will continue to be better. Obviously, earlier you need to check the gap between the spark plug electrodes. It is normal to set it by bending the L-shaped electrode to 0.5. 0.6 mm, narrower. Otherwise, the power of the magneto may not be enough, and the spark will be, as it is also called, weak, or it will not be at all.
Now let’s take a look at the magneto. If previously the lawn mower started up without much effort, then the brain will be limited to cleaning and checking the wires. In that case, there were earlier tasks, check the gap between the magneto and the flywheel. The smaller it is, the better the spark. But do not press the magneto tightly against the flywheel. There is a common method for checking and setting this clearance. Take a duralumin beer can and cut a strip out of it. Having loosened the magneto mount and laid a strip of aluminum between its poles and the flywheel, press the magneto and tighten the bolts. As a result, we pull out a strip with pliers. I have used this method many times and it always gave a positive result.
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And basically everything, our lawn mower is ready for summer work.
The design and principle of operation of the ignition system for a household chainsaw
Every saw that runs on a gasoline engine must be equipped with an ignition system. The main function of this unit is to timely ignite the fuel inside the cylinder. To do this, the ignition system of the chainsaw creates an electrical discharge that breaks through the space between the electrodes of the standard spark plugs. The correctness and efficiency of its engine operation largely depends on the serviceability of this unit of the chainsaw. In this regard, special attention should be paid to checking this important part of the tool.
The electronic ignition of a household chainsaw, as standard, consists of a number of the following parts:
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- spark plug;
- keys that turn off the motor;
- wiring connecting the elements to each other.
Magneto is a separate type of alternating current generator. When working, it creates electrical energy, and directs it to the spark plug of the chainsaw. The magneto device includes an inductor on which a stationary winding is wound. The element also includes a permanent magnet that is attached to the flywheel. When the chainsaw is operating, the flywheel rotates simultaneously with the engine crankshaft.
At the right time, a certain standard part of the device divides the existing contacts. This leads to a sharp increase in voltage and a spark flash between the electrodes of the factory spark plug.
This increases the risk of overheating of the contacts. To exclude this, as well as oxidation of the wiring, the electrical circuit of the standard ignition system is equipped with a capacitor.
The ignition circuit of a household chainsaw equipped with a contactless base magneto is based on the action of the control coil. It functions as a voltage flow regulator. The electronic unit of such an ignition system is supplemented with a capacitor, a diode and a thyristor. The latter is needed to pass a current with certain voltage parameters. During the opening of the thyristor, the capacitor begins to discharge, thereby creating a current inside the turns of the base primary winding.
After that, the current is converted into a high-voltage DC voltage, which creates a breakdown in the standard spark plug located in the cylinder. The standard electric chain of a chainsaw operates on the impulse principle simultaneously with the translational cyclic movements of the engine cylinder and the rotation of the crankshaft.
How to set the ignition on a chainsaw?
Adjusting the gap between the flywheel and the ignition coil on the chainsaw is required when the tool does not start. Immediately before adjustment, you need to check the condition of the spark plug. To do this, you need to remove the wires from the head and carefully unscrew the part from the socket with a special key. If the candle is not wet, and small light spots of oil are visible on its ceramic walls, then you need to proceed to the next stage of the check.
To do this, you need to put a cap with standard wiring on the candle and pull the starter rope sharply several times. If, at the same time, the spark did not appear, then you should proceed to adjusting the gap between the flywheel and the magneto.
An infringement of the clearance between these parts of the chainsaw may cause careless handling of the tool. In standard form, the distance between the magneto and the flywheel should be no more than 0.2 mm. It is quite easy to check this value. To do this, you will need to place a special gasket between the elements. If it freely enters the space between the elements, then the gap is set correctly.
Many craftsmen claim that it is possible to correctly adjust the ignition on a chainsaw only using a template. However, not every tool owner can afford to purchase a disposable product at a fairly high price. Many gardeners use homemade stripe templates cut from a flat plastic juice container.
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Further adjustment of the ignition of the chainsaw is performed in the following order:
- First you need to loosen the system fixing bolts;
- After that, a template should be inserted between the standard ignition coil and the built-in flywheel;
- At the end, the fixing adjustment bolts will need to be tightened.
How to check the ignition coil of a chainsaw?
Often, the cause of the malfunction of the tool used is not only the wrong clearance between the existing standard flywheel and the standard coil, but also in the breakdown of the latter. In this case, you will need to carefully check the coil.
- inspect the condition of the coil body and make sure that there are no cracks or other defects on it;
- check the cleanliness of the coil elements and the electrical wiring connected to it;
- inspect the condition of the insulation of the wires;
- evaluate the reliability of fasteners;
- inspect the condition of the cap, which forms a spark;
- check the condition of the candle;
- check the operation of the candle switch;
- use a multimeter to check the voltage inside the node.
Check the coil in this order:
- First you need to measure the resistance that the magneto creates. This method is used if the owner of the chainsaw knows the optimal parameters. When forming the required pulse, it will be necessary to separate the indicators formed by different semiconductor elements. In this case, a sign of a malfunction is the ringing of the circuit through the minus and the high-voltage wire. As a result, the measuring device shows an overestimated resistance or an open circuit;
- Next, you need to use a device that will make it possible to check the operation of the candle and the presence of a spark. It will need to be connected at the point where the circuit is broken between the spark plugs and the high-voltage wire. The disadvantage of this method is that the device required for testing is quite expensive.
Another way to check the coil does not require the use of expensive instruments. It is only used when the owner of the chainsaw no longer has options for diagnosing the ignition system. When checking from a candle, you will need to throw off the cap and insert a small nail into it. After that, the cap must be put on the candle so that the distance between the nail and the cylinder is about 6–7 cm. After that, the saw must be started and the spark must be inspected. If the coil is in good condition, the spark will be bright blue. Other shades of spark will indicate a malfunction of the magneto.
Coil repairs should be done in a clean, dry place. In this case, it is necessary to exclude the ingress of dust, oil or other liquids on the parts of the mechanisms. Otherwise, there will be a risk of short circuiting, which will lead to complex breakdown of the tool assembly.