Chainsaw union do-it-yourself repair

In detail: Union chainsaw do-it-yourself repair from a real master for the site my.housecope.com.

Image - Do-it-yourself chainsaw union repair

A chainsaw is not such a complicated device. However, in the event of a malfunction, it is necessary to have at least basic knowledge in order to find and eliminate the defect that has arisen.

Let's look at the main malfunctions of chainsaws, find out what they are connected with, and also analyze the basic steps to fix breakdowns.

The most important thing before proceeding with the repair is the correct definition of the malfunction. And there can be several reasons for the inoperability of each element. Therefore, before you start disassembling the chainsaw, you need to try to determine what the failure is due to.

As a rule, failure in the operation of chainsaws is caused by a malfunction of the engine or the occurrence of breakdowns in its other components.

Engine failures include:

  • ignition malfunction;
  • malfunctions in the fuel supply system;
  • piston or cylinder failure.

In other units, most often malfunctions occur due to failures of the brake mechanism, lubrication system, operation of the clutch, tires, etc.

Let's look at both groups of faults so that you can, if necessary, determine the cause of the breakdown on your own, without contacting a repair shop.

In the operation of the engine, the following defects are most often observed:

  • the engine does not start at all;
  • starts, but immediately stalls;
  • does not develop the necessary power;
  • works unstable.

To find the cause of the problem, you need to analyze the possible causes in order by elimination. Let's go through this chain so that you know how to find a defect in a chainsaw if it occurs.

Malfunctions in the ignition system most often cause the engine of a gas tool to fail. Therefore, you should start troubleshooting with it.

Examine the candle. To do this, carefully remove the high-voltage wire from the head, and then unscrew the candle from the socket using a special key.

Video (click to play).

If the plug is wet, then there is an excess of fuel. Most often, the supply of excess fuel is associated with improper carburetor adjustment or problems in the ignition system.

The candle should be carefully wiped with a dry paper towel and dried. You also need to drain the cylinder, close the fuel supply and run the starter several times to remove excess fuel mixture.

After these steps, you need to install the candle in place, open the fuel supply and try again.

Image - Do-it-yourself chainsaw union repair

If there is a noticeable amount of black soot on the candle, this usually indicates a malfunction in the fuel supply - a violation of the gasoline / oil ratio, low-quality oil, or the need to adjust the carburetor.

In this case, the candle must be cleaned with a needle or a sharp awl from accumulated soot, cleaned with a zero-sandpaper until a metallic sheen appears and screwed back into place. In this case, you need to pay attention to the tightness of the candle gasket.

If the chainsaw still does not start, you need to check for a spark in the spark plug. With the high-voltage wire cap on, lean the spark plug skirt against the cylinder and pull the starter, as shown in the photo below:

Image - Do-it-yourself chainsaw union repair


If a blue spark jumps from a distance of 2-3 mm, then everything is in order. If the spark appears only at a distance of 0.5 - 1 mm, most likely there is a malfunction in the ignition system. If there is no spark, you need to check the high-voltage cable with a probe. Perhaps there was a wire break in it.

If all the actions performed did not lead to success, try changing the spark plug to a known good one and try starting the chainsaw again.

Also, the absence of a spark may be due to a violation of the gap between the ignition module and the flywheel magnetic circuit. The gap should be 0.2 mm. The required clearance can be set using a 0.2 mm gasket, which is placed between the flywheel and the ignition module.

A video of the chainsaw ignition device and its malfunction is shown below (click the triangle to play):

If everything is in order with the ignition system, then go ahead and check the fuel supply system of the chainsaw.

The failure of the fuel supply system is usually due to one of the following reasons:

  • fuel filter contamination;
  • the hole in the tank cap is clogged;
  • insufficient amount of incoming fuel mixture.

We disconnect the fuel hose from the carburetor and see if fuel flows out of it or not. If the fuel flows in a free stream, then everything is in order - the cap and filter are working properly. If the fuel mixture does not flow at all or flows very weakly, then we clean the opening of the cover (breather) with a needle.

We remove the fuel filter through the filler hole, with a hook (can be bent out of the wire), together with the suction hose. The fuel tank must first be emptied. The filter is disconnected and cleaned or replaced with a new one.

It is recommended to change the fuel filter every 3 months. As for the insufficient amount of the fuel mixture coming from the carburetor into the cylinder, the reason here may lie in the violation of the ratio of fuel and air mixed in the carburetor. The main reasons: clogging of the air filter, clogging of the channels of the carburetor or mesh filter.

Of course, when repairing chainsaws, it is necessary to clean the air filter, as it gets dirty pretty quickly. This reduces the amount of air entering the carburetor. The fuel mixture at the outlet in this case is excessively enriched.

The dirty filter must be removed very carefully so that the accumulated dirt does not fall off and enter the carburetor. The filter must be cleaned or washed in water and detergent. Then dry and install back.

If all the actions described above did not lead to success, perhaps the reason for the inoperability of the chainsaw lies in the malfunction of the carburetor.

In this case, it is checked and adjusted. However, if you do not have experience in performing such work, then you should find a specialist through friends or an ad who knows how to do it. Otherwise, you risk being left without a saw. A carburetor is a device consisting of many parts of a very small size, which, if disassembled ineptly, can simply fall out and be lost.

A video on how to repair a Stihl MS 250 chainsaw carburetor is presented below.
(click triangle to play):