How to set clearance on the trimmer spool

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..

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 picture below shows how they look.

clearance, trimmer, spool

The flywheel has an impeller that acts as a fan to cool the engine. There are also permanent magnets on one side of the flywheel, 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.

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.

  • 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..
  • Connect one electrode of the tester to coil ground and the other to the lead coming out of the magneto. Normally, the resistance should be between 0.4 and 2 ohms.
  • To check the secondary winding, you will need to set the device switch to 20 ohms. 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).

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

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.

  • Remove the cap from the candle. You do not need to unscrew the candle in order to maintain compression..
  • A nail without a cap must be inserted into the cap. The nail should be of such a diameter that it adheres well to the cap..
  • Tie the cap with the nail 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 in no case touches the “mass”).
  • Using the starter, simulate the engine start several times. The ignition button must be on.
  • Observe if a spark appears and what color it has.

Normally, the spark should be strong, white or bluish. 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 malfunctions, it ceases to produce current. As soon as the coil cools down, the trimmer starts up again and runs for a while until the magneto warms up again. This coil needs to be replaced.

Sometimes a spark plug can cause a similar heating problem even if the coil is OK, so both parts need to be checked..

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 candle 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 spark 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.

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 could 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 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 bad 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..

Basically, ignition adjustment is about setting the correct gap between the magneto and the flywheel..

Ignition adjustment algorithm

Trimmer ignition is quite simple to adjust.

    Remove the engine cover from the engine by unscrewing all the bolts holding it. For example, on a Patriot (Patriot) PT 2540 lawn mower, to remove the cover, you will need to unscrew the air filter housing, and use a flat screwdriver to remove it from the latches. After that, the plastic case can be easily removed.
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How to Reload a DeWalt Quickload™ Spool Quick Guide

  • 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 the 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. After that, the ignition on the trimmer will be adjusted..
  • The principle of operation of the carburetor lawn mowers

    The throttle valve determines the amount of air to be supplied, and the power of the motor directly depends on this..

    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 candle 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 spark 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.

    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 could 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 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 bad 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..

    Basically, ignition adjustment is about setting the correct gap between the magneto and the flywheel..

    Trim Ignition Adjustment

    Do-it-yourself lawn mowers carburetor adjustment

    Lawn mowers, like all gas powered garden tools, are not difficult to maintain. It is possible and necessary to repair, configure without the help of others. For example, adjusting the carburetor for lawn mowers with your own hands is a matter of 5 minutes.

    A lawn mower carburetor is a unit in the power system. In it, like all carburetors, there is a process of mixing air and fuel (gasoline) for the forthcoming supply to the engine cylinders.

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    In this process, the main thing is the correct proportion of fuel and air, which is why they regulate the carburetor.

    Read also from the heading

    Trimmer ignition setting

    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..

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    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.
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    Chinese lawn mower won’t start We climb into the carburetor

    Diy lawn mowers carburetor adjustment

    Setting up the module does not apply to repair and replacement of spare parts is not required. In this case, the lawn mowers carburetor repair kit will not be needed..

    Three screws are provided for debugging:

    • L – is regulated first, since it is responsible for supplying fuel at low speeds;
    • H – he is responsible for the supply of gasoline at high speeds, as well as for fuel consumption and temperature;
    • T – it is used to debug idle.

    There are options, as a rule, this is the carburetor of a Chinese lawn mower, when only one screw remains on the body for debugging – for adjusting the idle speed. This does not mean that the module is configured automatically – it means that it will be difficult to carry out even such a type of repair as debugging. In the photo – adjusting the carburetor of a Chinese lawn mower.

    • The module is configured only when the engine is warm: for this, the device is pre-switched on for 10 minutes. If the mowing head rotates at idle speed, then the debugging is started immediately: turn the screw T counterclockwise until the rotation stops.
    • Adjustment begins with screw L. The screw is turned to the right and left until it is found such a position at which idle speed does not become maximum.
    • Then the screw is turned ¼ turn counterclockwise. This will be his working position..
    • Idle speed must be adjusted by turning counterclockwise to increase the number of revolutions and clockwise to decrease it. Its debugging consists in achieving such a mode in which a sufficient number of revolutions are made before the start of rotation of the mowing head. In this case, the engine must work stably at different positions.
    • The position of screw L is determined last – at maximum speed, the trimmer should not work for more than 10 seconds. The throttle opens, the screw turns clockwise, very slowly, until a decrease in the number of revolutions is audible.
    • Then, also slowly, the screw rotates counterclockwise until the motor starts to malfunction. Then the screw is turned back clockwise until the engine starts working normally again..

    If there is a tanometer, and if the recommended rpm values ​​are indicated in the product passport, the correction can be made more accurate, focusing not on hearing, but on the readings of the device.

    The adjustment of the carburetor of the lawn mowers in the video was carried out by ear.

    7 comments on the post “Adjustment and repair of the carburetor lawn mowers”

    • Dmitry Pavlovich 07/04/2016

    Please clarify. In the adjustment section p. 5, screw L – error? Should you read screw A? Thank you.

    prompt the initial position of the screws H L LA

    SHOW START POSITION

    prompt the initial position of the screws H L LA

    Thank you very much for the video about the accelerator and did not know, but the defect is very important and creates a huge problem that almost everyone is silent about. BRAVO….

    Maybe all the same tachometer is a rpm meter, and not a tonometer blood pressure meter

    and I have L, H, LA, it’s LA instead of T?

    The heart of any chainsaw is a two-stroke internal combustion engine..

    The trimmer is not a complex household appliance, so most of its floor.

    There was a need to purchase a reliable and reliable mechanical tool.

    Gone are the days of Soviet agro-industrial gigantomania. Gig gone.

    Tiller is an economical tractor option for small-volume jobs.

    Tiller Neva is produced today in different modifications, this one is specialized.

    Fuel supply adjustment

    Idle speed adjustment

    Following the adjustment of the fuel supply, we take up the idle speed adjustment. To do this, the corresponding screw must be adjusted so that the engine runs slightly accelerated at low revs. But it is necessary to monitor the immobility of the reel with fishing line and knives. Before starting their movement, there should be a few turns in stock. The movement of the spool and knives can subsequently lead to rapid wear of the clutch. Noticing that the engine does not start well, you need to increase the number of idle revolutions. As the revs increase, the fuel mixture is saturated with air, which leads to a loss of power.

    The main signs of correct idling:

    • Stock of turns for the trimmer head;
    • Uninterrupted operation of the engine even when changing position (sharp rise or fall of the knife);
    • Quiet operation of the engine on a cold run;
    • No increased rpm of a hot engine.

    How to store your lawn mower properly and avoid problems with starting it

    Its launch depends on the correct approach to storing the trimmer. And this applies not only to winter long-term storage. How to properly store a gasoline trimmer, in order to warn yourself against problems with the difficulty of starting it, you must take into account a number of the following recommendations:

    • Before storing the tool in the zipun for winter storage, drain the fuel from the tank. In addition, the remaining fuel must also be removed, and this can be done by starting the engine, letting it run for a while until it stalls
    • Store the tool preferably in a dry place.
    • Before starting the engine after a long pause of more than 2-3 months, it is necessary to first inspect the spark plug electrodes, as well as check the main components – the air filter, high-voltage wire, etc.
    • When operating the tool, it must be borne in mind that overheating of the motor negatively affects the service life, so you need to take breaks during work, especially if a trimmer with a two-stroke engine is used for work. Units with four-stroke engines are not only more powerful, but also more durable
    • After winter, the first thing to do is to pour a little oil into the plug hole, first moving the piston to the dead center. This is necessary in order to lubricate the parts of the CPG when starting the motor, thereby eliminating their rapid wear.
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    Only with the right approach to finding the reasons why the trimmer does not start can you find and fix the breakdown yourself. Moreover, for this you do not need to be a specialist at all, and to understand thoroughly the design of gasoline units. Proceed in order in the sequence presented in the material, and it will be as easy as shelling pears to restore the lawn mowers to work..

    Trimmer clutch malfunction

    On all gasoline trimmers, a centrifugal clutch is installed, the meaning of which is that the pads, when you add speed, begin to disperse and cling to the cup. The easiest way to check the clutch is to unscrew the rod from the motor, usually 4 bolts. If the pads are worn out, the clutch needs to be replaced, a metallic grinding is heard. If your trimmer has traction and the line is constantly rotating, then the spring is stretched..

    Principle of operation

    The throttle valve determines the amount of air to be supplied, and the engine power directly depends on this..

    Fuel is sucked into the carburetor system by a pump (its membrane). Then it passes through the choke in the carburetor. The fluid then flows through the pump inlet and outlet valves. Filtered by the grid. Moves through the needle valve into the diaphragm chamber.

    Step-by-step operation of the device:

    • Air supply to a tube with an air baffle (damper). The baffle regulates the intensity of the air flow.
    • The fuel supply system is necessarily narrowed by a diffuser to increase the flow rate.
    • Gasoline through the float chamber and the nozzle tube with a constriction. A float chamber adjusts the temporary volume of gasoline. In the float chamber, the pressure level is neutral, and in the tube with a constriction it is already low. Due to the differential pressure, the fuel penetrates through the nozzle.
    • The acceleration of the air flow facilitates the transfer of fuel (gasoline) and its atomization. As a result, an air-fuel mixture of the required proportion or density is formed..
    • The air / fuel mixture enters the engine cylinder through the fuel pipe.

    Simply put, adjusting the carburetor on a lawn mower is about creating an optimal fuel mixture through the correct air supply..

    The throttle valve determines the amount of air to be supplied, and the power of the motor directly depends on this..

    Fuel is sucked into the carburetor system by a pump (its membrane). Then it goes through the choke in the carburetor. Then the liquid moves through the inlet and outlet valves of the pump. Filtered by the grid. Moves through the needle valve into the diaphragm chamber.

    • Air supply to a tube with an air baffle (damper). The baffle regulates the intensity of the air flow.
    • The fuel supply system is necessarily narrowed by the mixer to accelerate the flow.
    • Gasoline through the float chamber and the nozzle tube with a constriction. A float chamber adjusts the temporary volume of gasoline. In the float chamber, the pressure level is neutral, and in the tube with a constriction it is already small. Due to the pressure drop, the fuel seeps through the jet.
    • The acceleration of the air flow facilitates the transfer of fuel (gasoline) and its atomization. Ultimately, an air-fuel mixture of the desired proportion or density appears..
    • The air / fuel mixture seeps into the engine cylinder through the fuel pipe.

    Simply put, adjusting the carburetor on a lawn mower is about creating a good fuel consistency through the correct air supply..

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