How to Remove the Husqvarna Trimmer Head
One of the most important parts of any chainsaw is the cylinder-piston group (CPG), which transmits rotational motion to the drive sprocket. Despite the reliability of this unit, most models require diagnostics and repairs over time. It is the performance of the CPG of the chainsaw that determines the power of the unit, its ease of starting, the presence of idling and the fuel consumption.
Causes of Piston Chainsaw Problems
There are many reasons for the failure of the CPG, which can be divided into two main categories: natural wear and tear. The first type of malfunction, as the name implies, is the physical wear of the rubbing parts of the piston group. The second category is more extensive and implies:
Elements of a piston chainsaw
- severe overheating of the internal combustion engine and, as a result, the appearance of thermal seizures on the piston surface;
- breakdown of the lower part of the piston (skirt) due to the duration of the chainsaw at maximum speed;
- ingress of foreign particles into the combustion chamber and the occurrence of mechanical damage to the CPG;
- breakdown of the compression (piston) ring due to heavy wear or exceeding the permissible revolutions of the saw;
- mismatch of the recommended servings of gasoline and oil when preparing the fuel mixture.
Worn Chainsaw Piston
Experts do not recommend disassembling a CPG without any particular reason. However, if the tool has significantly lost power, a metallic ringing has occurred in the internal combustion engine or the crankshaft does not crank when the starter jerks, a piston chainsaw should be diagnosed. First of all, to identify engine problems, it is necessary to measure the compression in the cylinder. With a significant deviation from the values recommended by the manufacturer, we can safely say that there are scratches, working out, and scuffing on the surface of the cylinder or piston. It is the drop in compression that is the basis for the complete disassembly and repair of the piston group of the chainsaw.
For the on-line diagnostics of the CPG for breakage of the compression ring of the chainsaw or scoring in the cylinder, professionals are advised to remove the muffler and assess their condition through the exhaust window.
Chainsaw Piston Group
Video: How to Remove the Husqvarna Trimmer Head
The dimensions of the cylinder-piston group are determined primarily by the diameter of the piston made of heat-resistant aluminum alloy. Regardless of the model, the CPG of a chainsaw consists of a cylinder, a piston, a holding finger and two clamps.
Chainsaw Cylinder Mirror
When buying a piston chainsaw, you should pay attention to the inner surface of the cylinder, which should be polished and have a glossy shine. In the presence of damage, scratches, experts do not recommend installing such a cylinder.
In order to increase compression in the working unit and, as a result, increase power, many manufacturers install two piston rings. The compression rings of the chainsaw made of special cast iron fit snugly against the cylinder, as a result of which the tightness of the combustion chamber is ensured.
Piston Chainsaw Replacement Algorithm
If it is time to replace the CPG chainsaw, you need to know that for each specific model there is an individual algorithm of actions. To facilitate disassembly / assembly, it is necessary to prepare a candle wrench, a large flat screwdriver, a hammer, a compressor for cleaning the parts of the unit, a set of open-end and end wrenches. Regardless of the manufacturer and the design features of the model, before removing the chainsaw cylinder, the following work must be done:
- Dismantling the upper protective cover;
- Unscrewing the spark plug;
- Side cover removal;
- Using a large flat screwdriver, the stoppers are removed from the shock absorbers;
- In the channel of the candle we put a lace to fix the crankshaft and unscrew the clutch and the flywheel nut;
- Dismantling the drive chain sprocket;
- We remove the carburetor with an air filter;
- Remove the ignition module and exhaust system.
After removing from the base of the power unit, unscrew the pan and remove the crankshaft with the piston from the cylinder. Using a pair of tweezers or a screwdriver, dismantle the piston pin stops.
Before dismantling the piston, it is necessary to remember its location in the cylinder, so that subsequently you do not waste time re-disassembling and assembling the power unit.
Sealant for fixing the chainsaw chainsaw
Before starting assembly, it is necessary to clean the parts and components of the unit from dirt, residues of sawdust, dust with compressed air, rags and other means. The first step in replacing a piston chainsaw is to install a piston on the crankshaft. We fix it on the connecting rod with a steel finger, which is supplied with the CPG. In order to prevent arbitrary loss of the retaining rings, it is recommended to install them cut down. Next, we mount the compression rings on the piston, but due to their fragility and fragility, this operation must be approached as carefully as possible. To prevent the formation of scratches before installing the piston in the cylinder, lubricate the piston with oil. Before installing the crankcase (pan), you will need to degrease its mounting surface and apply a layer of heat-resistant sealant. We assemble the chainsaw in the reverse of the above algorithm.
Often replacing the piston of a chainsaw, crankshaft and compression rings solves the problems with idling and the problematic start of the engine.