How to Connect a Tachometer to a Chainsaw

Manual chainsaws are currently widely used both for felling trees, cutting knots and further harvesting firewood, as well as in the construction of wooden houses and various buildings for household purposes. Like any other tools, these devices (rather reliable) require regular preventive maintenance, and sometimes tuning. For example, a tachometer for a chainsaw will allow you to easily not only check the characteristics of a newly purchased tool, but also make subsequent carburetor adjustments yourself.

The principle of operation of the tachometer for a chainsaw

A tachometer is a device that measures the number of engine revolutions in one minute. It is almost impossible to connect a mechanical device to a tool with a gasoline engine (and it is not necessary). A modern tachometer for a two-stroke chainsaw engine is a digital device that reads pulses from a candle insulator or high-voltage wire at the time of sparking (without direct contact). The built-in microprocessor converts the pulses into engine revolutions. Indications are displayed on a conveniently readable liquid crystal display. Depending on the manufacturer and design features, the price of such devices varies from 950 to 6500 rubles.

Wired tachometers for chainsaws

The most common instruments for controlling the engine speed of a chainsaw are models with a wired connection. Their popularity is due to the low price. A variety of models of electronic tachometers for chainsaws from the Chinese manufacturer Runleader now cost 950-1850 rubles.

To measure engine speed with such a device, it is necessary to provide access to the high-voltage wire of the plug, which (depending on the model) can be connected in two ways:

• Using the clamp, which is located at the end of the cord included in the kit;
• By means of a winding (5-6 revolutions of the free end of the cord around the high-voltage wire), fixed with a plastic clamp or insulating tape.

Wireless engine speed meters

Convenient to use are tachometers for chainsaws, allowing you to control engine speed without connecting a wire. Such measuring instruments measure the engine speed at a distance of 15-20 cm from the insulating cap of the candle. The undoubted advantage of such measuring devices is that when setting up the carburetor, there is no need to dismantle the protective cover and the air filter. But these devices are much more expensive than their wired counterparts.

In the Russian market, the most affordable are wireless tachometers from leading manufacturers of chainsaws “Husqvarna” and “Stihl”: Husqvarna PET-302 and Stihl EDT-9.

These devices are quite versatile. Measurements can be made at different distances from the candle cap:

• At a distance of 5-10 cm, using only the device itself;
• 15-20 cm, connecting a short wire-antenna (15 cm long) to the device;
• 1.2 m, using a measuring cord with a clip for mounting on a high-voltage wire of a candle.

In what cases is the carburetor adjustment of the chainsaw required

Along with such preventive work as replacing a spark plug, fuel or air filter, periodically there is a need to adjust the carburetor of the chainsaw. This must be done when:

• The new chainsaw unstably runs on fuel available to the user;
• The saw does not start;
• High or low idle;
• The saw starts and stalls immediately;
• Fuel consumption declared by the manufacturer has increased significantly;
• When loosening the fixation of one or more adjusting bolts;
• After repairing the carburetor or replacing it with a new one.

How to Connect a Tachometer to a Chainsaw

What to look for before starting adjustment work

Before starting any adjustment work, you must carefully read the instructions for the chainsaw. It indicates the engine speed (at idle and the maximum allowable), which must be set when adjusting the carburetor for the correct operation of the tool. The uptime is largely dependent on this.

The air filter must be thoroughly cleaned or replaced. You should also make sure that the candle is working, and the necessary gap between the electrodes is set.

Important! Before starting the setting, we warm up the saw idling for 8-12 minutes

Setting carburetors low-powered chainsaws

On low-powered chainsaws (for example, the fairly popular Stihl MS170 and MS180 models with an engine capacity of 30-32 cm³) carburetors are usually installed with only one adjusting screw.

On the body, it is indicated by the Latin letters LD. It is designed to adjust engine speed in idle mode. Setting up such a carburetor can be done both with and without a tachometer for measuring chainsaw revolutions:

• Twist the adjusting bolt all the way;
• Unscrew it two turns;
• Start a chainsaw.

If the idle speed is underestimated (this is indicated by the tachometer readings or the engine is unstable), then turn the screw until the saw chain begins to move. Then unscrew it ½ turn back (that is, in the opposite direction).

If the idle speed is too high, and the chain starts to move immediately after starting the engine, then turn the screw until it stops and make another ½ turn in the same direction.

Chainsaw carburetor adjustment with tachometer

The largest number of chainsaws “Husqvarna”, “Stihl”, ‘Partner”, “Champion” (and also from numerous Chinese manufacturers) has three spring-loaded adjusting screws on the carburetor.

They are indicated in Latin letters and are intended:

• L. To adjust the fuel supply at low speeds.
• H. To set the amount of fuel at maximum speed.
• T (on some LA models). Decrease or increase the supply of the air-fuel mixture at idle.

For work, you will need a thin slotted screwdriver and a tachometer to adjust the chainsaw.

On a note! For the convenience of counting the revolutions of the adjustment screws, it is better to apply a clearly distinguishable mark on the screwdriver handle in advance.

The setup algorithm is pretty simple:

• If a wired tachometer is available, then remove the protective cover and air filter to provide free access to the high-voltage wire. When using a wireless meter, this is not necessary.
• We start a chainsaw.
• We connect the tachometer (or we bring the wireless device close enough to the candle).
• By turning the screw L we achieve the highest idle speed. Then do ¼ turn counterclockwise.
• If the circuit moves in this mode, then by rotating the screw T (LA) we achieve its complete stop.
• Push the accelerator handle all the way.
• We give the saw to work in this mode for 8-10 seconds.
• According to the tachometer, we set the maximum revolutions recommended by the manufacturer using screw H.
• Using the adjusting bolt T, set the necessary idle speed.
• By pressing and releasing the throttle, we make sure that the tool works in all modes smoothly, without dips and jerks.
• Turn off the tachometer.
• We replace the air filter and the protective cover.

Finally

Without even having great technical capabilities, but having a tachometer for a chainsaw, adjusting the carburetor is quite simple. It does not take a lot of time. Of course, if you wish, you can contact a service center to carry out such work. However, the services of professionals will cost significantly more than the purchase of a simple digital device. Yes, and time will be spent much more. In addition, adjustments (even minor ones) may be needed when changing the brand of fuel, a sharp change in humidity or ambient temperature. And here you can not do without a small, but very useful instrument for measuring engine speed. The choice of a specific model of an external tachometer depends on both personal preferences and the financial capabilities of the user.