The rotor (flywheel with magnets) spins on the shaft of the Master Danila chainsaw, creates the magnetic field for the ignition coil and cools the cylinder with its fins.
Replace it if there are cracks, the magnets have lost strength, or the key or fins are damaged. Signs: weak spark, unstable ignition, runout. The fit and the key must match the crankshaft of your saw.
After replacement, check the unit at idle and under load: there should be no leaks, play or unusual noises.
