Lawnmower repair with their own hands: analysis of faults and troubleshooting methods
An indispensable tool of the modern gardener or owner of a private house is a lawn mower, which allows you to effectively and efficiently bring the adjacent territory in order. The period of active use of brushcutters falls on late spring until October. Modern units are equipped with powerful and durable internal combustion engines, reinforced transmission and basic units. Despite this, physical wear and tear, manufacturing defects or improper use leads to grass trimmer failure. In order to make the grass trimmer repair with your own hands, you should have at least basic knowledge in the field of technology and a little experience in its repair.
The main component of any gasoline tool is the internal combustion engine (ICE), which transfers the torque to the actuator by various means. In modern gasoline grass trimmers as a transmission element between the motor and the trimmer head is used duralumin rod (pipe), inside which the drive shaft is located.
Thanks to the highly revolving motor, the frequency of line rotation can reach 13 thousand revolutions per minute, depending on the manufacturer of the grass trimmer. In order to avoid mechanical and thermal damage to the gearbox, its housing has a special opening for the introduction of grease in the form of ointment. All brushcutter models have a sturdy shoulder strap to make it easier to use over long periods of use.
Malfunctions of electric motors and troubleshooting
The fact that the electric motor of the grass trimmer is out of order is evidenced by:
To reanimate the motor of the electric hand-held grass trimmer with his own hands, its owner must have some knowledge in the field of electrical engineering, understand the device of the electric motor and have experience in troubleshooting, which arise during the operation of complex household products.
Important! Diagnostics and troubleshooting begin with visual inspection and testing of power supply cable with a multimeter. If damage is detected, it is repaired.
Next you need to check whether ~220V voltage is supplied to the motor contacts when the trigger is pressed. If there is voltage, it means that it is the motor that is out of order. Otherwise the starting button is defective and should preferably be replaced.
Most often, the electric motor loses its performance due to faulty bearings. In normal conditions, the rotor should rotate freely within the stator. However, lack of grease in the bearings, lubricant starvation or dirt ingress can cause the rotor to rotate with difficulty. In some situations, it may even jam. Also, a loud noise when the motor is running may indicate that the bearings are broken and need to be replaced.
Before attempting to repair the motor, it is advisable to inspect it carefully for damage. These include:
- The presence of dirt and foreign objects inside the motor;
- Darkened paint inside the motor, which will indicate severe overheating;
- chips and cracks on the external surfaces of the motor;
- Broken structural elements.
Any faults detected should be corrected if possible. afterwards it is recommended to carefully wipe the collector plates and brushes with a cloth dampened with alcohol. If the graphite brushes are badly worn they are replaced with new ones. If there are potholes or burnt out areas on the collector plates, the latter are machined and polished.
The magnetic circuit of the electric motor is made of special high-strength steel and can only be broken by extreme loads. Therefore, when repairing the electric motor all the attention is paid to the integrity of the windings and their insulation, as well as the reliable contact between the mating parts. Check the integrity of the windings as follows:
- set the switch of the type of work of the multimeter in the mode of measuring resistance (the lowest limit);
- hold the probe of the multimeter against the graphite brushes or directly against their contacts.
Important! The multimeter should show not more than 100 ohm of resistance.
If it shows infinite resistance, it is advisable to rotate the motor shaft without removing the feeler from the brush contacts. If at this multimeter will show a resistance within the range from 10 to 40 ohms, then the stator winding is intact, and if it is less than 5 ohms, then there is an inter-turn short circuit, which usually occurs when the motor overheats strongly.
Defects of electric trimmers
As mentioned above, the electric group of trimmers has its own typical set of faults, along with problems common to all hand-held mowers. See below for a troubleshooting guide.
Assembly and disassembly
For most machines, disassembly is the opposite of assembly. Electric mowers are no exception. So here are the instructions for assembly, and disassembly will be carried out in reverse order.
- First you need to connect the protective cover with the multi-faceted wrench from the kit.
- To mount the head with a fishing line should align the holes in the gear cup and the hub, fix them with a locking rod. Then you need to unscrew the nut clockwise and remove the cup shaft, leaving the hub. Then you need to screw the head with the fishing line all the way counterclockwise. The blade is also mounted on the hub, but there is a cup and a nut on top.
- To assemble the grass trimmer rod, it is necessary to connect its two parts. Once you are sure that the locking mechanism is in the hole, you need to tighten the wing nut.
- Use the large bolts in the kit to attach the rod to the motor.
- Screw the handles at an equal distance from each other in the knot of attachment on the boom.
This part of the electric trimmer quite often fails. To check its performance use an ohmmeter or other circuit testing device. If there is no resistance, the part must be replaced. It is not uncommon for the plug, socket or wiring to be at fault.
For your information! Sometimes the breaker doesn’t trip because of the thermal switch to protect the motor from overheating, but the problem is in the button.
At the “heart” of the electric trimmer, the armature, stator, bearings and temperature sensors should be checked for malfunctions. Also check the windings and check the state of the brushes and contacts. Burnt-out windings are expensive to repair. It’s better to change. Worn brushes must also be replaced. Contacts can be repaired by yourself with a soldering iron. A problem with a motor is often signaled by burning smell, arcing and vibration.
Mechanical faults are typical for an electric lawnmower, such as the following.
- If the motor works but the cutting tool doesn’t rotate, it means that the flexible shaft is broken. To replace it you need to unscrew the rod and remove the damaged part. If necessary, you will have to disconnect the lower part of the grass trimmer.
- It is not uncommon for the boom itself to break. During work, it can be temporarily secured with improvised objects. But later you will have to buy a new stand.
- Often when repairing you have to deal with cutting tools, especially the line reel. To avoid unnecessary problems, you need to learn how to properly tuck the string.
- Quite often you need to replace the bearing of the main shaft for the cutting tool, because it breaks.
To Note! Mechanical faults can occur in the main segment of the grass trimmer, where the main nodes are located. They can be in the nature of chips or cracks. Replace or repair such parts. will prompt the degree of seriousness of the breakdown.
If you suspect an electrical problem, you should carry out diagnostic measures using special measuring instruments. The simplest is a test screwdriver. It allows you to determine if there is current in the circuit. To get more reliable results, you need a multimeter.
So, if the electric grass trimmer doesn’t work, you will need to disassemble the handle of the machine. Your electrical appliance readings will tell you the culprit. Lack of resistance leads to the replacement of the part. There may still be breaks in the power cable or damaged contacts which you can repair with your own hands.
So, the improper use of electric and gasoline trimmers leads to the problems that were mentioned above. In order to minimize unit failures, it is necessary to follow the manufacturer’s instructions. There is no need to try to squeeze everything out of the machine. Observe work and rest routine. Lubricate problematic parts in a timely manner. Clean and maintain your helper as often as possible. You can visually see one or another repair process of manual mower on the corresponding video on the network.
Making a reel by yourself
Grass trimmer is often operated at a distance from places where you can buy spare parts for the mowing head when it breaks. In this case, instead of a broken mechanism can be installed simple design spool, made with their own hands. You need a sheet of plywood (textolite, metal, etc.), a pair of eyelets and screws.), eyelets, screws or screws. The process involves several steps.
- From a plywood sheet cut out a disk with a diameter corresponding to the failed bobbin.
- In the center of the disc drill a hole that matches the diameter of the shaft of the grass trimmer.
- On opposite sides of the disk mount small eyelets that will serve for filling the fishing line.
- The line for the trimmer is passed through the eyelets and fixed with the usual screws or screws. The coil is ready to work.
- Clamping the manufactured bobbin between two washers, it is attached to the shaft of the trimmer for grass with a nut.
Trimmer Clutch Removal
Important! Remember that you can’t tighten or unscrew the nut without rigid fixation of the shaft.
To change a line on a homemade reel it is necessary to release fixing screws, to insert a new piece of a line and to tighten fastenings again. It is not necessary to remove the spool from the shaft of the grass trimmer, but it is necessary to exclude the possibility of spontaneous start of the motor.
So, above were described step by step with pictures of methods of repair string head. As you can see, this process is not complicated. And most breakdowns are directly related to the sloppy filling of the string and its poor quality. You can visually see all the steps in the process can be seen in the video.
If the engine won’t start
When the lawnmower does not start, you must first check whether the tank did not run out of fuel. If everything is okay, you need to check its quality. perhaps you bought a cheap type of gasoline, which does not suit the equipment. For a grass mower, it is best to use good gasoline, which is purchased at gas stations, the brand should not be lower than AI-92.
It is not worth saving and buying cheap fuel, as this will lead to the fact that the cylinder-piston group will fail, and you can spend much more money on repairs than on high-quality gasoline.
It is also very important to prepare the fuel mixture correctly and combine oil and gasoline in the right amounts. The proportions should be specified in the manual. This is why it is so important that it is written in Russian, because there is a possibility that different models of mower require several different proportions for successful operation.
It is not necessary to use the fuel mixture in large volumes, because if you keep the unused volume indoors for a long time, it will lose its properties. It is better to use a freshly prepared solution.
- Engine performance can be a problem if the fuel filter is clogged. First of all you have to check the filter. Replace it if necessary. Never leave the inlet pipe without the fuel filter. You should also check the air filter. If it is dirty, you should take it off, rinse it in gasoline and put it back. If you are in a cottage or a private house, it is enough to wash it in clean water, using a variety of detergents. After that rinse, squeeze and let dry. The ready filter is wetted in a small amount of oil, which is used for mixing. The excess is removed by squeezing the filter with your hands. The part can then be put back in.
- If all these procedures did not help and the engine still does not start, you can try to adjust the idle speed, for this start tightening the carburetor screw. It is very similar to the adjustment of a similar part on the car. If there is no experience in adjusting the carburetor, you can study videos on the Internet that are very clear and accessible. There will clearly show how you can make adjustments to the lawnmower carburetor with your own hands.
Replacing piston rings without removing the engine, video, with your own hands
The fact that the car needs exactly the replacement of piston rings, and not some other repair work, will tell the engine itself. Signs of such malfunction are quite pronounced, so it will be difficult not to notice them. But before we talk about the symptoms, we need to understand what the rings are, and what role they play in the operation of the engine.
What are piston rings and what do they do?
Piston rings are elastic, loose elements that are installed in special grooves in the piston housing. They are made of high-strength steel or cast iron, and coated with an alloying material on top. The alloy coating further increases durability, and also reduces the rate of wear.
Usually there are 3 rings inserted into a piston: 2 compression rings (occupying the top 2 grooves) and 1 liner ring (bottom groove).
The job of the compression rings is to prevent hot gases from escaping down the length of the piston into the crankcase. Wiper ring. removes excess oil from the cylinder bore, preventing it from entering the combustion chamber.
the rings also reduce the temperature of the piston, transferring approximately half of its surface heat to the cylinder walls.
When piston rings fail to cope with their assigned tasks due to their wear, the car engine signals this with corresponding symptoms.
If the wear has reached a critical stage, it is indicated by blue or black smoke from the exhaust pipe. This indicates that the excess oil got into the combustion chamber past the oil ring and burned there with the fuel. Black smoke coming out of the crankcase ventilation tube indicates that the compression rings are allowing gases to escape from the combustion chamber into its cavity due to wear.
Critical wear is accompanied by a decrease in compression (ability to hold pressure) in the engine cylinders.
This means that part of the gases formed during combustion of the fuel mixture, which should have pushed the piston, burst into the crankcase, not making useful work.
Exactly this will lead to a pressure drop in the cylinder, therefore the engine will lose some power. Increased oil consumption is observed.
Compression is checked with a special device. a compressometer.
When the nominal values of pressure are unknown (no instruction manual), first it is measured in a dry cylinder, then some engine oil is poured through the spark plug hole and the measurement is done again. If the compression increases, it means that the rings need to be replaced. Similar signs can be observed in the case of their “stagnation”.
Such a problem, if the case is not too severe, can be corrected with special fuel additives. An engine that has a carburetor system can be tried to clean with a decalcification spray, which is injected directly into the carburetor. If removing the soot from the combustion chamber had no effect, there is only one way out. replacement of piston rings and cleaning of the grooves.
How to replace the piston rings yourself
Of course, replacing the rings is a rather time-consuming procedure. It requires accuracy and certain skills, but by and large there is nothing complicated about it (if you do not remove the engine). It requires:
- remove the cylinder head, following all the car manufacturer’s recommendations;
- drain oil, remove flywheel protection and engine crankcase pan;
- remove the oil intake;
- turn the crankshaft to set the correct piston at the bottom dead center
- Unscrew the cap of the connecting rod and remove it;
- pull the piston together with the connecting rod out of the cylinder, pushing it up with a wooden rail;
- clean the piston of carbon deposits. According to its marking determine the class of the piston, buy a new set of piston rings corresponding to it;
- Each new ring is first inserted into the cylinder to check the clearance in the lock before installation. the clearance must be as specified in the vehicle owner’s manual. If it is smaller than necessary, the ends of the lock are carefully filed down with a nail file;
- the pistons are carefully cleaned of carbon deposits. The oil drain holes are also cleaned with a suitable wooden stick. Lubricate the cleaned grooves with clean engine oil;
- the rings are put on, beginning with the linchpin. The rings are marked “TOR” (up) on one side to show how they are to be installed in the piston. Locks should be installed 120 degrees in relation to each other. This prevents gases from leaking through. Do not put the rings “by the coil”, such installation can be accompanied by the appearance of microcracks, which will lead to their breakage;
- Reassemble in the reverse order, cleaning everything in parallel with a clean rag and lubricating with fresh engine oil. Pistons must be installed in the exact cylinders from which they were removed. The crank pin caps and bearing shells must also be put on the same crank pins from which they were removed.
If the wear of the crank pins can reuse them, then do not do replacement, because this will need to bore crankshaft journals. By yourself such work without experience qualitatively perform it will not work.
- a set of open-end wrenches and ring spanner, as well as a screwdriver with an extension and sockets rated from 10-19;
- A torque wrench;
- special. crimp (mandrel).
In addition, you will need an oil-resistant sealant. It is needed for installing the crankcase pan and valve cover gaskets.
And there seems to be nothing complicated in the actions listed above, if the replacement is performed without removing the engine from the car. However, there are nuances, without taking into account which an engine with new rings will not run for a long time. When the cylinder reaches the extreme stage of wear, a “step” is formed on the surface of its mirror.
When hitting it, the new ring will either break immediately or get a crack, which will eventually lead to its breakage anyway. In addition, the grooves of the old piston also have wear and tear, so lapping the new rings to the cylinder will be difficult or even impossible.
Features of operating a gasoline trimmer for grass
It is worth noting that such a grass trimmer can work for a long enough period with proper operation. In different sources come across photos of lawnmower repair, where it is described in maximum detail how it is carried out.
The repair of the gearbox, or rather its timely lubrication, as well as the need for periodic changes of trimmer’s fishing line, and finally, it is necessary to check the teeth at the end of each work.
To perform these simple actions, you do not need to contact specialists, because it is easy to do them yourself.
But before you start to carry out repairs with your own hands, it is recommended to read in detail the annotation, which is attached to any model of trimmer for grass at the purchase. There, by the way, will be also indicated parameters of a fishing line for the following changes.
What to do if the engine won’t start?
If you can’t start the mower, the first thing to do is to check the presence of fuel in the tank and its quality. To fill the tool, it is recommended to use high-quality gasoline, purchased at gas stations, the brand of which should not be lower than AI-92. Saving on cheap fuel can break the cylinder and piston assembly, which can cost a third of the value of the brushcutter. No less important is the correct preparation of the fuel mixture of gasoline and oil. The proportional ratio of these components of the mixture is specified by the manufacturer in the manual. It is not necessary to prepare the fuel mixture in large volumes, because during long storage its properties are lost. It is better to use freshly mixed fuel.
When preparing the fuel mixture, oil is poured into the gasoline with the help of a medical syringe, which allows you to exactly observe the required proportion of components
A dirty fuel filter in the tank can also prevent the lawnmower engine from running. So if you have trouble starting the engine, check the condition of the filter. Replace the filter, if necessary. Do not leave the inlet without the fuel filter.
The air filter should also be checked. If dirty, remove the part, wash it in gasoline in the field, and replace it. In the country house or at home, the filter can be rinsed in water using a detergent. Rinse, squeeze and dry the filter afterwards. After the filter is dried moisten it with a small amount of oil that is used to prepare the fuel mixture. Use your hands to squeeze out excess oil. Then reinsert the part. The cover that has been removed is put back in place and screwed on.
The air filter washed in fuel mixture, squeezed and dried is installed in its place in a plastic case and sealed with a cap
How to do this procedure in more detail you can see at
If all the above procedures are performed, and the engine will not start, then adjust its idle speed by tightening the carburetor screw. In the video at the beginning of the article we pay a lot of attention to this.
Grass trimmer kinematic diagram: how torque is transmitted from the engine to the mowing head. where breakdowns occur
The overhead electric grass trimmer, like the gasoline engine trimmer, has two torque transfer designs through the form-fitting boom:
The straight boom is used on the more powerful and expensive trimmers. I have a more budget version, but it works reliably. I’ll start with this one.
The upper part of the rod is inserted into the housing. It is secured with mounting screws on opposite sides. two diametrically located.
A hole for a self-tapping screw
The spring shaft rotates inside the mower, and its free end is inserted into the adapter sleeve.
Directly transmits the rotation. On powerful trimmers there can be an upper gearbox, which increases the power of effort at the expense of the number of revolutions, so necessary when mowing bushes and young trunks.
My personal opinion: It’s better to cut wood with a saw. not a trimmer with an electric motor or gasoline motor.
I have a collapsible boom. Two-piece design, so the electric mower can be transported in a regular car.
Marketers think it is a useful feature, but I have never used it in 6 years, except for the case of disassembly to show you this construction by photo.
The spring bending capacity, even under its own weight, is clearly visible below.
Please note that there should always be a special lubricant on it. It sharply reduces the possible friction force of the shaft against the inner walls of the metal tube, excluding its damage.
The second shaft, located in series below, is exactly the same. But it needs lubrication to a greater extent: it works inside the curved tube and should be lubricated better.
The shaft fits into the slide bearing mounted inside the bottom of the rod. On the lower end is a spool of fishing line.
By the way, an electric motor of 800 watts and a 1.6 mm line is quite enough for me on my trimmer to regularly mow the grass around the cottage. The power of 1.85 kW and the thickness of the line of 2.4 mm are too much for my purposes. The work goes faster, though.
I’m showing you the details of how the fishing line reel is mounted on the output shaft with another picture.
By the end of the sixth season of use I wiped the factory reel to the ground to the ground, and the line for the trimmer completely cut through the metal bushes and came out of its plastic walls.
I tried to repair it, but it’s not effective: it’s useless. On the photo is already second, bought reel with fishing line of my mower.
The plain bearing (when there are no balls or rollers, but just a calibrated hole in the sleeve) is not the best technical solution. On my trimmer it is already worn out and needs to be replaced.
There are practically no such bushings on sale. It is necessary to remove and order them from a turner.
On Yandex Zen channel I show a step-by-step replacement of the line inside the spool in the form of a narrative.
Design features of trimmers with a straight bar
The motor rotation inside the rod is transmitted by a solid shaft instead of a spring one: more reliable in operation. It can be one or consist of two parts, which allows better transportation of the assembled trimmer elektricheskogo grass trimmer.
The solid shafts have rolling bearings, and this greatly extends the overhaul period and life of the product.
Grass trimmer with a straight boom can have an upper gear, docked to the shaft of the electric motor. The pinions in it are cylindrical.
An alternative option is the lower arrangement of the gearbox with the output of torque directly to the mowing head: bevel gears.
Any gearbox design transmits rotation by gears and requires their lubrication. Without it, friction increases sharply and as a consequence, the wear and tear of the mechanism increases: it does not last long.
Trimmer Repair Replacing the Clutch Drum || Trimmer Clutch Removal Brush Cutter| Replace Drive Shaft
To lubricate the gearbox of a grass trimmer use only special grades of trimmer grease: they work better.
I do not use the cutting disk for mowing bushes on my gasoline mower, and it is not available on the electric trimmer. That’s why I don’t publish any information about its operation.
I will conclude my article here. In my opinion, other parts of a grass trimmer break less often and do not need complex repair, like belt drives. For example, I simply replaced the broken buckle with a hand-made piece of wire.
I want to invite you to participate in a short survey and give your personal opinion, which will help the following site readers.
An interesting solution to repair the electric grass trimmer is offered by Malusha in her short video, abandoning the soft starter motor device. Do you think such a decision is justified??
Another useful video concerns the elimination of increased vibration of the grass trimmer. MasterLom solved this issue on its own and in an original way: changed the thread size, made additional adjustments.
If you still have questions about the brushcutter, use the Комментарии и мнения владельцев section. Right now is the most convenient time for you to do it. I will definitely give you an answer.
Chief editor of the site. Specialization: electrics, mechanics, copywriting.
in the photo you can see the yellow box resistor, one end is on the switch, and I accidentally ripped off the other end and can’t find where. Tell me where the other end comes from?