Woodruff Key 9 x 3.7 x 3 mm – Precise Fixation for Flywheel of Puch, Sachs, Beta and Zündapp

The Woodruff key (also called a disc spring) with the dimensions 9 x 3.7 x 3 mm is an essential small part for the correct positioning of your flywheel on the crankshaft. It ensures that the ignition timing is maintained precisely by fixing the flywheel in the precisely defined groove. This key is universally compatible with many classic engines such as Puch, Sachs, Beta and Zündapp. As this component is often lost during the removal of the flywheel or shears off due to a loose nut, it is advisable to always have a spare in the workshop.

Technical Data and Compatibility

With a width of 3 mm and a height of 3.7 mm, this key fits perfectly into the standardized grooves of common moped crankshafts. Made of hardened steel, it withstands mechanical stresses while also serving as a predetermined breaking point to prevent greater damage to the crankshaft in case of a blockage.

Installation and Maintenance Tips

• Check Fit: Before inserting, thoroughly clean both the groove in the crankshaft and the groove in the flywheel with brake cleaner. Both areas must be absolutely grease-free so that the cone of the crankshaft can transfer the force – the key primarily serves for guidance, not for force transmission.

• Insertion: The key should sit without play in the groove. If it falls out easily, you can secure it with a tiny drop of grease to prevent it from slipping when the flywheel is pushed on.

• Control: Check the key during every ignition revision. If it shows grooves or deformations, it must be replaced immediately, as otherwise the ignition timing will shift and the engine will lose power or may not start at all.