In this video, we show you how to replace the cylinder and piston on a Stihl TS420 disc cutter.

Health & Safety Warning - Please ensure that you have safely prepared the machine and workspace. If you are unsure about any aspect of the task please seek professional advice.

Transcript

Today we're going to change the Cylinder and Piston on a Stihl TS420 Disc Cutter. To do this you need to get the machine down to a short engine. We have linked our video on how to do this in the description below. Once that's done you can continue with this tutorial. Using a 13mm spanner loosen the decompression valve. You can now completely free the valve by screwing it off by hand. Turn the short engine upside down. Remove the four screws based in the crankcase to detach the cylinder from the machine using a torx spanner. When doing this, take note of which way the cylinder is facing as this will have to be placed back in the same way. This will then reveal the cylinder gasket. Remove the gasket by hand. As you're taking it off, make a note of how the gasket is placed. Once the gasket is off, use a pair of pliers and remove the spring which sits inside the piston. Now that is removed, use a tool to help push out the piston pin, carefully free this from the machine. Then finally remove the needle bearing which sits within the crank, make sure you don't loose these components. Before fitting the piston, it's good practice to lubricate the crank with some oil. This can help the machine run smoother. Then place the needle bearing through the crankshaft, again lubricate it with some oil. When placing the piston back in position, you need make sure the arrow is pointing towards where the exhaust will be fitted. Place the piston over the crank and turn the engine on its side. While on its side push the pin through the centre of the piston. Then using the pliers, place the piston spring back into position. Ensure that the springs is secure and in the correct position. Now, place the new cylinder gasket in position. Once in position you are ready to put the cylinder back on the machine. However, before doing this you must ensure the gaps in both of the piston rings are centred around the marks on the piston. As a tip use some oil to lubricate the piston before placing the cylinder over it. Make sure the piston rings are in the correct position,Now place the Cylinder on top of the piston, ensuring it is the correct way. The exhaust port should be facing the way the arrow is pointing on the piston. Which is where the exhaust will be seated. Once it's on the machine push it down and turn the crank to make it more secure. While holding the cylinder, turn the machine upside down. Now using a torx spanner screw in the four screws to secure the cylinder and piston in place. Make sure it's secure. That's how you change a Cylinder and Piston on a Stihl TS420 Disc cutter.

Parts

Parts and tools included in the TS420 disc cutter how-to video.

• Non-Genuine Cylinder & Piston Assembly - 410 200
• Genuine Cylinder & Piston Assembly - 4238 020 1207
• Non-Genuine Recoil Assembly - 410 217
• Non-Genuine Exhaust Silencer - 410 607
• Non-Genuine Clutch - 400 219
• Genuine Torx Wrench/Plug Spanner - 4224 890 3400
• Piston Stop Tool - 350 103