No Spark On Trimmer

Trimmer Ignition Adjustment How does the trimmer ignition system work and why is it necessary to adjust it? Algorithm for checking magneto. How to correctly set the gap between the magneto and the flywheel.

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.

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.

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.

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.

Then we move on to dismantling the parts from the back of the carburetor. As mentioned earlier, unscrew the two bolts. This is already an air supply system.

A valve is located here, which opens when gas is added and increases the flow of air into the engine.

After removing it, a bare body remains in the hands. The carburetor is disassembled.

Identification of faults and their elimination

Now it is worth paying attention to the problems that occur during the operation of the carburetor and how to fix them.

Step 9

How to purge. The most effective way is to use an ultrasonic bath.

It is filled with either a special liquid or gasoline, a carburetor is placed there and under the action of ultrasound, the so-called cavitation effect, the channels are cleaned of contamination.

The second option for cleaning is compressed air.

You can use the compressor available on the farm and clean the carburetor channels. However, this method is effective if the pollution is not very large.

Step # 3

Now we remove the membrane. It is she who performs the function of pumping fuel into the carburetor.

When the membrane vibrates, the other side exerts pressure on the rocker arm of the mechanism and the needle rises, which, in turn, opens the hole and fuel is supplied.

Step # 8

Now we need to get the needle.

To do this, unscrew the bolt on the mechanism, holding it with your finger. The fact is, there is a spring there and a careless action will lead to the fact that it is lost.

We take out the needle and the spring.

Problem 2: Clogged fine filter

It is located on the carburetor cover and is a fine metal mesh. Its pollution occurs very often. This is due to the deposition of oil, additives, dirt on it.

Problem 4: wear of the button-bubble for manual fuel priming

Problem 3: membrane failure

Step # 4

Remove the carburetor cover with the injection mechanism.

Step 14

In addition, the bubble button for manual fuel pumping may fail. The impact of gasoline on it leads to the fact that during prolonged operation, the rubber corrodes and it begins to stick together or, under the influence of low temperatures, for example, during storage, it bursts. The button should also be replaced if necessary. In addition, its cost is small and will not affect the size of the repair budget in any way.

Based on the foregoing, it can be concluded that there are only three main carburetor malfunctions: clogging of channels, contamination of the fine filter and failure of components. In the first two cases, cleaning is enough, and in the third, a repair kit will help.

Carburetor repair motocross step by step

Very often, complaints from owners of gasoline trimmers are associated with various kinds of carburetor malfunctions. Of course, in this case, it is best to seek help from specialists in this field, for whom the repair of carburetors of gasoline trimmers is an integral part of the profession. However, if you are still familiar with the basic principles of the trimmer carburetor, you can try to figure out the problem yourself so as not to overpay money in the service, since sometimes the breakdown can be really frivolous.

This article is just intended to help you deal with the problem.

Next, we will analyze the most common breakdowns and the reasons for their occurrence.

The first step is to generally inspect the carburetor and find out if there is a fuel leak.

If it turns out that there are no problems with fuel, it is necessary to remove the carburetor from the engine and check the condition of the gasket located next to the carburetor.

If no malfunctions are observed here, you can try to check the carburetor for tightness.

To do this, you can purchase a special device, which is part of the tool kits for repairing the carburetor repair of mowers and representing a special pressure gauge that, in fact, checks the tightness.

If you don’t want to spend money on its purchase, you can use a conventional medical tonometer, on which you just need to change the pressure gauge.

When using this device, pay attention to the indication.

If the pressure does not drop and remains the same for a long time, you can rest assured, as this indicates the tightness of the carburetor.

If the pressure begins to decrease after a certain time, then there are still problems.

They can be associated with damage to any parts of the carburetor.

Assembling the carburetor

Assembling a brushcutter carburetor is a snap. It is necessary to perform all actions in reverse order:

Step 12

Sometimes, when disassembling on the nets, a certain film is found. Therefore, the carburetor does not have enough fuel and the brushcutter either does not start, or works intermittently. Cleaning methods are identical to the first reason: an ultrasonic bath, a compressor or a spray bottle with a special solution. In addition, if the mesh is clogged thoroughly, you need to take a soft brush for watercolors, soak it in gasoline and rinse it carefully without damaging it.

We carry out diagnostics of a candle and a candle channel

If the quality of the fuel mixture is not in doubt, and the brushcutter stalls when starting, then a flooded candle may be the cause. Here, for repairs, an ordinary candle wrench is suitable (every motorist probably has) and a spare candle.

  • We unscrew the candle and wipe it;
  • Dry it thoroughly (do not ignite);
  • We drain the excess fuel in the chamber through the spark plug hole and dry it;
  • We clean the old candle from carbon deposits using a file or a lady’s file;
  • We expose a gap with a distance of 1 mm (you can check with any coin);
  • We put everything back in place and try to start the trimmer.

If the candle is working, the socket where it is located is completely dry, and the petrol cutter does not want to start, lubricate the threaded connection with gasoline. It should be slightly damp. No matter how wonderful a spark the candle may give out, there is simply nothing to ignite in a dry chamber.

If the trimmer motor still does not start, you should exclude such a reason as the absence of a spark due to poor contact between the spark plugs and the high-voltage wire. If the connection is good and there is still no spark, most likely your ignition unit has flown. Here it will not be possible to do without a master, since the part is not repaired, but sold as a single unit.

Breather and exhaust port

Often, delicate branded petrol brushes do not start and stall due to a dirty breather. The main function of this element is to equalize the pressure in the gas tank. When this unit becomes clogged, a vacuum is created in the tank, preventing the supply of fuel. You can eliminate the malfunction by cleaning the breather. You can use a regular needle for cleaning.

Normal operation of streamers with internal combustion engines can be disrupted due to dirt entering the exhaust channel or a clogged silencer mesh. There is such a problem on older generation models. The issue can be resolved by traditional cleaning and removal of the anti-spark grid.

Diagnostics of filters for petrol cutters

Another reason why the gasoline scythe stalls is the air filter. To eliminate it, try removing the filter and starting the trimmer without it. If possible, then you will have to change the air filter to a new one, or at least blow through and thoroughly clean the old one.

The petrol trimmer may not start if the fuel filter is dirty. This is the next step in our algorithm. Here we check the condition of the filter element and, if necessary, replace it with a new one. When replacing, try not to leave the suction pipe completely without a filter, this is prohibited by any operating instructions. Haste can turn into repairing the engine piston group.

How to start diagnostics of brushcutters

If the brushcutter does not start or immediately stalls after starting, it is necessary to sequentially check all the main components and assemblies. The verification algorithm is as follows:

  • Fuel tank (fuel quality);
  • Candle and candle channel;
  • Air filter;
  • Fuel filter;
  • Breather;
  • Outlet channel.

These nodes are most often the source of major problems that can be eliminated after a thorough inspection.

Why the petrol cutter won’t start troubleshooting

Caring for the personal plot, summer residents periodically encounter the fact that the petrol cutter does not start. There are many reasons for tool failure. For the correct diagnosis of the problem, the owner of a useful unit in the country needs to know the device and the principle of operation of its individual parts.

  • How to start diagnostics of brushcutters
  • Checking the fuel mixture
  • We carry out diagnostics of a candle and a candle channel
  • Diagnostics of filters for petrol cutters
  • Breather and exhaust port
  • Complex reasons for the failure of petrol cutters
  • Rules for the operation and storage of petrol cutters

Complex reasons for the failure of petrol cutters

If the step-by-step troubleshooting algorithm does not work, and your scythe still does not start or stalls, it is worth inspecting the carburetor and the engine itself. A clogged carburetor can be one of the reasons for erratic tool performance. There are three main problems here:

  • Clogged ducts or nozzles. All this is cleaned by special washes or blown by a powerful jet of compressed air from the compressor. Do not use needles and wires, as the bore may be damaged;
  • Worn carburetor gasket. Exit replacement of a failed gasket;
  • Violation of tightness. To check this indicator, you can use an ordinary household tonometer, replacing it with a suitable pressure gauge. Watch the readings: if they do not change everything is fine, but if the pressure starts to drop, then some part of the carburetor is faulty. We’ll have to find it and replace it with a new one.

If everything is in order with the carburetor, then the petrol trimmer may not start due to wear of the piston group. If chips, scratches or scuffs are found, the piston or cylinder should be replaced. Piston rings are subject to mandatory checks. A small backlash of the piston when rocking the connecting rod indicates that it is time to change the rings. It is best to entrust this procedure to the specialists of the service center.