How To: Stihl TS410 & TS420 Cylinder and Piston Rebuild

How To: Stihl TS410 & TS420 Cylinder and Piston Rebuild

Posted by David Schatz, Owner - DHS Equipment on Aug 17th 2014

Stihl TS410 & TS420 Premium Cylinder Overhaul Kit | 4238-020-1202

Step-by-Step Instructions on How to Replace the Cylinder and Piston on a Stihl TS410 and TS420 Cut-Off Saw.

For your convenience, DHS Equipment has assembled these step-by-step instructions for rebuilding the top end of your Stihl TS410 and Stihl TS420 saw. Using the Stihl TS410 and TS420 cylinder overhaul kit sold on our website, you can easily replace the cylinder and piston on your TS410 or TS420 saw. 

While you're replacing the cylinder and piston on your TS410 or TS420 saw, you should inspect other internal parts along the way for wear or damage. If you're in need of other replacement parts, please visit our Stihl TS410 and TS420 parts section, or call 866-611-9369.

Step 1: Remove the three 13mm nuts from the starter housing. Remove the starter assembly. 

Step 2: Remove the belt guard cover. Release the belt tension by loosening the clamping lever.

Step 3: Remove the arm assembly by sliding it off the 3 studs used to secure the starter assembly.

Step 4: Remove the muffler. There are 3 screws that secure the muffler, 2 on the top, and 1 on the bottom.

Step 5: Use a flashlight to inspect the top of the piston and piston rings through the exhaust port. Look for knicks in the piston, loose or missing piston rings, scratches in the piston or any other type of damage. 

Step 6: Remove the air filter cover and air filter.

Step 7: Remove the 4 screws in the top shroud, 2 on each side of the handle. 

Step 8: Remove the spark plug cover.

Step 9: Disconnect the throttle rod from the throttle trigger.

Step 10: Carefully move the engine kill switch wiring out of the way.

Step 11: Lift the shroud cover off the saw. 

Step 12: Remove the 4 screws in the flywheel cover and remove the flywheel cover from the saw.

Step 13: Remove the 2 cylinder cover screws. 

Step 14: Remove the 2 screws in the ignition coil module and move it out of the way. 

Step 15: Remove the 3 carburetor mounting screws. There is 1 above the air filter housing, and 2 inside the air filter housing.

Step 16: Slide the choke lever off its post and remove the choke lever and choke rod from the saw.

Step 17: Lift the carburetor straight up and out of the engine. 

Step 18: Loosen the clamps on the top intake manifold, and on the bottom intake manifold. Carefully take a screwdriver and pry the intake manifolds off the engine cylinder. Take special care to not tear or damage the Stihl TS420 intake manifold. 

Step 19: Flip the Stihl TS420 saw over to access the bottom. There is a handle clamp on the bottom of the saw that must be removed to access the 4th cylinder screw. Remove the handle clamp, and then remove the 4 cylinder screws. 

Step 20: Flip the saw back over to access the cylinder. Carefully pull the cylinder off the piston. 

Step 21: Inspect the piston and rings for damage. 

Step 22: Remove the piston pin from the piston and remove the piston from the connecting rod. 

Lay out the parts from our Stihl TS410 & TS420 Premium Cylinder Overhaul Kit, part number 4238-020-1202. Our premium Stihl TS410 & TS420 cylinder overhaul kit features a premium aftermarket cylinder that exceeds Stihl OEM specifications. Also includes, piston, piston rings, piston pins, and 2 piston pin clips. 

Step 23: Install the piston rings on the new piston. Take notice of the piston ring stops on each side of the piston. 

Step 24: Install 1 spring clip for the piston pin into the piston.

TECHNICAL NOTE: On the top of the piston, there is an arrow. That arrow instructs you on how to install the piston. The arrow should face the exhaust port on the Stihl TS420 cylinder. 

Step 25: Insert the piston into the cylinder, (be sure that the arrow on top of the cylinder faces the exhaust port), far enough to compress the piston rings, but leaving the piston pin hole accessible to receive the piston pin and second spring clip.

Step 26: Place your cylinder base gasket on the crankcase.

Step 27: Carefully slide your piston and cylinder over the piston rod, lining up the connecting rod and piston pin holes. Slide the piston pin through the piston and connecting rod. Install the second spring clip into the piston. 

Step: 28: Before completely inserting the piston into the cylinder, double check that your spring clips are seated in the grooves provided in the piston. 

Step 29: By turning the flywheel, lower your connecting rod to bottom-dead-center. 

Step 30: When your connecting rod is at the bottom of it's stroke, lower the cylinder and piston assembly into place on the cylinder base gasket. 

Step 31: Turn the saw on it's side while holding the cylinder. Reinstall the cylinder screws in an 'X' shape pattern. Top left, bottom right, top right, bottom left. 

Step 32: Once the cylinder is correctly torqued down, add a small amount of 2-stoke oil through the spark plug port to lubricate the piston in the cylinder. Spin the flywheel to check that there is no binding and that the piston moves smoothly inside the cylinder. 

Reassemble the saw using steps 1-18 in reverse.