Lawn Mower Magneto Gap

Lawn Mower Magneto Gap Engine Honda GX 390.Specifications, Operating Instructions

Honda GX 390 Engine Specifications

Manufacturing plant HAMAMATSU FACTORY
Model GX390K1
engine’s type Carburetor, 4-stroke, OHV, single cylinder, 25 ° tilt angle
Working volume 389 cm 3
Bore and Stroke 8 x 64 mm
Maximum power / At speed 10.0 kW (13.0 HP) / 3600 rpm
Net power 8.7 kW (11.7 hp) / 3600 rpm
Rated power 6.4 kW (8.6 HP) / 3000 rpm
7.0 kW (9.4 HP) / 3600 rpm
Maximum torque / At speed On the crankshaft 27 Nm (2.7 kgf-m) / 2500 rpm
With gearbox 1: 2 54 Nm (5.4 kgf-m) / 1250 rpm
With gearbox 1: 6 162 Nm (16.2 kgf-m) / 420 rpm
Compression ratio 8.0: 1
Fuel consumption 313 g / kWh (230 g / hp-h)
Cooling system Forced air
Ignition system Transistor Magneto
Ignition moment Fixed, 25 ° to a.M.T.
Spark plug brand Options: BP6ES, BPR6ES (NGK) W20EP-U, W20EPR-U (ND)
Carburetor With horizontal flow and butterfly valves
Air filter Options: Double element, oil bath, centrifugal type
Lubrication system Splash lubrication
Engine oil volume in the lubrication system 1.1 l
Recommended oil For general use, a viscosity of SAE 10W-30 is recommended. The other viscosities shown in the table may be used when the average temperature in your area is within the appropriate range.
Launch system Manual or electric starter
Stop system Grounding the primary ignition circuit
Fuel used Motor gasoline AI-92
Gas tank capacity 6.5 l
Oil volume in gearbox Reducers 1: 2, 1: 6 Lubricated from the crankshaft
Oil type Use the same oil as recommended for SAE 10W-30 engine
Direction of rotation of the PTO shaft Counterclockwise (looking from the end)
The nominal value of the clearance between the valve and the rocker arm Inlet valve 0.15 ± 0.02mm
Exhaust valve 0.2 ± 0.02mm
Nominal idle speed 1400 ± 150 min-1 (rpm)

Modifications of the GX 390 motors

There are many different modifications for this engine from Honda to meet the needs of any user. Varieties take into account the following parameters:

2.The presence of the gearbox and its type

3.The presence of an oil sensor

4.Type of starter (manual, electric)

5.Other differences (fuel filter, air filter, muffler, charging coil, control unit, etc.)

Engine oil for Honda GX 390 engine

It is recommended to run the engine with an SAE 10W-30 engine oil that is suitable for all ambient temperatures. Engine oils with different viscosities shown in the table may be used provided that the average air temperature in your area does not exceed the specified temperature range.

Use Honda Four-Stroke Oil or an equivalent high detergent, premium engine oil that is certified to US auto manufacturers’ requirements for SG, SF / CC, CD oils per accepted engine oil classification or better. The belonging of engine oils to classes SG, SF / CC, CD will be indicated by these letter designations on the container.

Do not overfill the engine with engine oil. Check the oil level with the engine horizontal.

Gx Series Engine Gearbox Oil

Fill the gearbox with the same engine oil as recommended for the engine itself. Fill oil up to the upper maximum
marks on the dipstick (gearbox with gear ratio 1/2 and centrifugal clutch). Reducer with gear ratio 1/2
(without centrifugal clutch) and the gearbox with a gear ratio of 1/6 are lubricated with engine oil in the crankcase.

Spark plug. Recommended types BPR6ES (NGK) W20EPR-U (DENSO) Inspect spark plug, replace if electrodes are worn out or insulator is cracked. The gap should be 0.70.0.80 mm. Bend the side electrode if necessary.

Adjusting the carburetor for GX engines

1) Start the engine and allow it to warm up to normal operating temperature.

2) With the engine idling, turn the idle adjustment screw to the desired direction so that the engine runs at its highest speed.

Sometimes, if the carburetor is completely misaligned, you need to restore the original settings and then adjust the motor more accurately. Correct adjustment is usually achieved by unscrewing the idle speed adjustment screw the next RPM from the stop position (light touch).

Idle speed adjustment screw speed:

Float chamber with balancing hole, vented 2-1 / 4 turn

Float chamber with a balancing hole communicated with a diffuser 2-1 / 4 turn

3) After the idle adjustment screw is correctly installed, turn the throttle stop screw to obtain the rated idle speed.

Air filter maintenance

Double filter element, silent cyclone filter:

1) Unscrew the nut, remove the air filter cover and unscrew the wing nut. Remove the filter elements and separate them. Inspect both elements carefully and replace if holes or breaks are found.

2) Paper filter element. Strike lightly several times on the hard part of the filter element to remove excessive accumulated dirt, or blow through the filter element with low pressure compressed air (no more than 30 psi, 2.1 kgf / cm2) from the inside out. Do not try to clean the filter element with a brush. The brush will only rub dirt into the filter paper.

3) Foam filter element. Wash in warm soapy water, rinse and dry thoroughly. Soak the filter element in clean engine oil. Squeeze out all the excess. If there is an excess of oil in the porous filter element, then the engine will smoke a lot during the first start.

4) Direct light through the filter elements and carefully check their condition for transmission. Reinstall the filter elements if they have no through holes or tears. If the air filter continues to degrade engine performance, replace it with a new one.

Single element filter

1) Unscrew the wing nut, remove the air filter cover and the foam filter element. Carefully inspect the filter element and replace if any holes or tears are found.

2) Clean, rinse and oil the foam filter element.

Oil bath filter

1) Unscrew the wing nut, remove the air filter cover and the foam filter element. Carefully inspect the filter element and replace if any holes or tears are found.

2) Clean, rinse and oil the foam filter element.

3) Drain the oil from the air filter housing and wash off accumulated dirt with a non-flammable solvent. Dry the air filter housing.

4) Fill the air filter housing up to the marked level with the recommended engine oil for the engine (see the recommended engine oil details).

Honda official website https://www.Honda.Co.Ru from this site you can go to dealers:

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The official site of the general engine manufacturer Honda honda-engines-eu.com/ru. The site provides mainly technical support and contains a lot of technical information.

Official distributor of Honda engines http://g-p-e.ru/. Assistance in finding dealers for service and repair.

Overall dimensions of the Honda GX 390 engine depending on the power take-off shaft

Gearbox options for the GX 390 engine

Honda GX 390 engine.Technical specifications, instruction

For over 40 years, Honda has been supplying versatile combustion engines to OEMs worldwide.

Gx. Series professional general-purpose gasoline engines are specially designed for long and trouble-free operation in extreme conditions. Gxv. (Vertical shaft motors are used for lawn mowers, worm gear cultivators, etc.)

The gasoline engine Honda GX 390 is suitable for a wide range of applications in difficult conditions, for example, in construction equipment, cultivators, gas generators, power plants, welding machines, pumps and other industrial equipment.

The GX 390 is an OHV gasoline engine with an air-cooled 25-degree cylinder and a horizontal crankshaft. Displacement 389 cm 3, maximum power output 13 hp. (sometimes the operating instructions indicate the rated and net power, which is closer to real conditions). The maximum power is used more for advertising purposes.

The graph of the dependence of power and torque value depending on the engine speed.

As you can see, the nominal operating speed at which the engine provides the highest torque of about 2500 rpm. Some experts consider the amount of torque to be a more significant indicator than power. In addition, everything here is more unambiguous without tricks and gimmicks.

Wheeled petrol lawn mower. Prevention, repair, maintenance. Preparing for the season.

Any equipment, especially gardening, operating in rather difficult field conditions, requires maintenance. Even simple and minimal maintenance of it significantly increases the resource of this technique, and makes the work itself simpler and more pleasant. And the motors start up “half-at-a-time”, and work powerfully and without a rumble and bounce.

Such minimal maintenance of his equipment can be provided by the owner himself, without the need to take it to a specialized 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. Other lawn mowers will do much the same.

After last season and wintering in a cold barn, the mower needs both cleaning and lubrication. External cleaning was done in the fall, before storage, now it is necessary to carry out it more thoroughly and prepare the lawnmower for the battle with grass and weeds.

First of all, it is necessary to remove the protective covers from the petrol lawnmower engine. This will provide easier access to the main components and facilitate work. We will also be able to inspect the starter device, remove dust, dry grass particles and other debris from under the casing that interfere with the normal cooling of the engine. And it is, as you know, airy and its quality is influenced by the cleanliness of the engine.

The engine cover (in my MTD SP 48 model) is fixed with 4 self-tapping screws (item 1 in the photo). We pass the starter handle through the opening and remove the casing.

Now we can remove the starter device and access the main engine components. To do this, unscrew 3 screws that secure both the starter launcher and the fairing of the flywheel fan.

Carefully clean the starting device of debris and inspect the launcher cable. If it is damaged, you will have to change it to a new one by disassembling the launcher itself. A slight “disheveledness” of the cable can be restored with the help of some kind of elastic glue (rubber, PVA). Those. One that would glue the villi together, but at the same time the gluing site remained elastic.

Having removed the fan cowl, carefully clean the fairing and fan blades from debris using a stiff long-bristled brush. Now let’s move on to the engine components.

Ignition system.

The ignition system of a lawn mower is arranged as follows. A permanent magnet is integrated into the flywheel of the engine. When it “flies” past the magneto poles (pos. 2 in the photo), the magnetic flux closes and an electromotive force is induced in the magneto coil. With the help of an electronic circuit, this pulse is shortened in time and a powerful pulse is formed, sufficient for an electrical breakdown of the spark plug gap (item 1)

Namely, 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 in the previous season the lawn mower had to work well, then it is better to immediately replace it with a new one, and if the old one still looks decent. The new one will still be better. Of course, you must first check the gap between the spark plug electrodes. It is optimal to set it by bending the L-shaped electrode up to 0.5. 0.6 mm, no more. Otherwise, the power of the magneto may not be enough, and the spark will be either weak or not at all.

Now let’s get into the magneto. If before that the lawn mower started without problems, then the brain will be limited to cleaning and checking the wires. If before that there were problems, check the gap between the magneto and the flywheel. The smaller it is, the better the spark will be. But do not press the magneto close to the flywheel. There is an easy way to check and set this gap. Take an aluminum beer can and cut a strip out of it. After loosening the magneto mount and laying a strip of aluminum between its poles and the flywheel, press the magneto and tighten the bolts. After that, we take out the strip with pliers. I have used this method many times and it always gave good results.

Now let’s examine the braking system. (item 3 in the photo). It is designed to quickly stop the engine when it is turned off. The brake pad is pressed against the engine flywheel, while the ignition wire is shorted to ground.

Of course, both the shoe and the flywheel must be clean. If necessary, the brake pad is replaced or adjusted. The cable and the spring of the brake mechanism are also cleaned and lubricated. In this case, it is convenient to use the lubricant in aerosol cans.

Changing the oil in the crankcase. It should be done according to the instructions for the gasoline mower, but at least once a season, even if you mowed a little. Because the oil is oxidized and its lubricating properties deteriorate.

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. So that the old oil does not drain into the protective casing, a small groove is cut out of the plastic bottle along which the old oil will drain into the substituted container without staining the casing. When all the oil has drained off, the hole is closed and new oil is poured through the oil filler neck to the required level. Use oil with the viscosity recommended by the manufacturer. Typically 10W40 for 4-stroke engines. It makes no sense to use more liquid and expensive grades, since the engine does not have an oil pump and lubrication is carried out with oil mist. And the operation of the lawn mower takes place at positive temperatures. And expensive oils show their properties only in extreme situations.

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We assemble and install all casings in the reverse order.

The final stage of the “technical inspection” is the revision of the knives. In various forums, you can find mutually exclusive opinions, sharpen them or not sharpen them. I am a supporter of “do not sharpen”. Of course, if they have seizures and bends left by the stones that you tried to mow, then they must 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 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 tends to turn yellow and dry. And pinched off. Quickly overgrows, healing the wound. And thirdly, no matter how you sharpen the knives, after half an hour of work they will return to their normal working condition. Those. This will be a metal edge with a rounding of 0.5 mm in diameter. In this state, they will be workers for a very, very long time. The knife cuts the grass by the force of the blow, inertia, not sharpness. Therefore, only the most noticeable burrs should be removed from the knife with a file or an abrasive bar, and this will be enough.

Well, basically that’s all, our lawn mower is ready for summer work.

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 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 don’t 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. Attach 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.

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.

lawn mower magneto gap

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, there is early ignition of fuel.

It can also be 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 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.

Self-preparation for the season of the gasoline lawn mower

Almost any technique, but most of all. Garden, working in rather difficult field conditions, requires competent maintenance. Even simple and minimal maintenance. Significantly increases its useful resource of work, and the labor process itself makes it simpler and even more enjoyable. The motors will then start up “with a half-turn”, and will work powerfully, reliably, without a rumble or bounce.

The owner himself can provide minimal maintenance of his own equipment, without the need to visit a service center. Using this article as an example, we will tell you about the necessary work to be carried out on a gasoline lawn mower. Other gas-powered lawn mowers will do about the same.

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After last season and wintering in a cold shed, the mower needs both cleaning and good lubrication. External cleaning was done in the fall, before storage, but now it is necessary to carry out it more scrupulously and thoroughly prepare the lawn mower for the upcoming battle with grass and weeds.

First of all, you need to remove the protective covers from the gasoline lawn mower motor, which will provide easier access to the main components, as well as facilitate the work itself. You will be able to properly inspect the starter device, remove dust, dry grass particles and other debris from under the shroud that interfere with the normal cooling of the engine. And it, as you know, is airy, so the cleanliness of the motor affects its quality.

The engine cover is fixed with self-tapping screws. We pass the starter handle through the opening and remove the casing. Now you can remove the starter device and gain access to the main engine components. To do this, unscrew 3 screws that secure both the starter “launcher” and the fairing of the flywheel fan. Carefully clean the starting device of debris and inspect the launcher’s cable. In the event that you notice that it is damaged, you will have to change it to a new one by disassembling the “launcher” itself.

Light “tousledness” of the cable can be restored using any elastic glue (rubber, PVA). That is, one that would glue the villi together, but at the same time the gluing site remained elastic. Having removed the fan cowl, we especially thoroughly clean the fairing and fan blades from debris using a coarse long-bristled brush.

Ignition system.

The ignition system of a lawn mower is arranged as follows. A permanent magnet is built into the flywheel of the motor. When it “flies” near the poles of the magneto, a closure of the magnetic flux occurs and an electromotive force is induced in the coil of the magneto. With the help of an electronic circuit, this pulse is shortened in time and a strong pulse is formed, sufficient for electrical breakdown of the spark plug gap. Namely, the quality of the spark ensures the ease of starting the lawn mower motor.

Therefore, we carry out the following operations. First, unscrew the spark plug and inspect it carefully. If in the previous season the lawn mower had to do a great job, then it is better to immediately replace it with a new one, even if the old one still looks pretty decent. The new one will still be better. Of course, you need to check the gap between the spark plug electrodes in advance. It is optimal to set it by bending the G. Of the shaped electrode to 0.5. 0.6 mm, but no more. Otherwise, the power of the magneto may not be enough, and the spark will be either weak or not at all.

Now is the time to tackle the magneto. If the lawnmower has started without any problems before, then you can limit yourself to cleaning and visually checking the wires. If, however, there were still problems before, check the gap between the magneto and the flywheel. The smaller it is, the better the spark will be. However, do not push the magneto tightly against the flywheel. There is an easy way to check and set this gap. Take an aluminum beer can and cut a strip out of it. Having loosened the magneto mount, and having laid a strip of aluminum between its poles and the flywheel, we press the magneto and tighten the bolts. After that, we pull out a strip with pliers.

Next, we inspect the brake system. It is designed to quickly stop the motor when it is turned off. The brake pad is pressed against the engine flywheel, while the ignition wire is shorted to ground. Naturally, both the shoe and the flywheel simply have to be clean. If necessary, the brake pad is replaced or adjusted. It is also cleaned, and then the cable and the brake spring are lubricated. In this case, it is convenient to apply the lubricant in aerosol cans.

Changing the oil in the crankcase.

It must be done according to the instructions for the gasoline lawn mower, but at least once a season, even if you have mowed very little. As the oil is oxidized and its lubricating properties deteriorate.

To drain the old oil, the lawnmower is tilted towards the drain hole, placing a log or something else under the wheels. To prevent the old oil from draining into the protective casing, a small groove is cut out of the plastic bottle, along which it will drain into the substituted container without staining the casing. When all the oil has drained off, the hole is closed and new oil is poured through the oil filler neck to the desired level.

Oil with the viscosity recommended by the manufacturer should be used. It makes no sense to use more liquid and expensive grades, because the motor does not have an oil pump and lubrication is performed with oil mist. And the operation of the lawn mower takes place at positive temperatures. And expensive oils show their properties only in extreme situations.

The assembly and installation of all casings is carried out in the reverse order.

The final stage of a self-carried out inspection is a thorough check of the knives. On different forums you can find conflicting judgments, sharpen them or not sharpen them. As practice shows, it is better, of course, to stick to the latter option. Of course, if they have significant scuffs and bends left by the stones that you tried hard to mow, then they need to be removed.

But sharpening the edge to a razor sharpness does not make any sense. And the arguments here will be as follows. First, let’s say the trimmer line is generally round. And nothing, she chops the grass perfectly. Secondly, the grass itself is better when it is not cut, but pinched off. The cut end of the grass tends to turn yellow and dry quickly. And pinched off. Quickly overgrows, healing its wound. And, finally, thirdly, no matter how you sharpen the knives, after some half an hour of work they will return to their normal working state. That is, it will be a metal edge with a rounding of 0.5 mm in diameter. The knife cuts the grass by the force of the blow, inertia, not sharpness. Therefore, only especially noticeable burrs need to be removed from the knife with a file or an abrasive bar, and this will be quite enough.