Stihl TS 410 / TS 420 cut-off machine flywheel-overtightened projectile hazard recall (~2021)

## Affected machines This bulletin covers Stihl **TS 410** and **TS 420** cut-off machines (handheld concrete cut-off saws) manufactured **January 2021 through April 2021**. ### Affected serial-number range **189442634 through 190001700** for both TS 410 and TS 420 models. The serial number is on the machine identification plate. ## Issue A limited production run of TS 410 and TS 420 machines was assembled with the **flywheel-to-crankshaft connection overtightened**. Overtightening can damage the flywheel internally; a damaged flywheel can fail and **break apart while the engine is running at operational RPM**. A flywheel failure during operation poses a **projectile hazard** to the operator and to bystanders within the working envelope. Critically: > A damaged flywheel is not apparent from a visual inspection. In other words, owners cannot self-inspect their way out of the recall - the only way to confirm whether a unit is in scope is by serial number. ## What to do 1. Locate the serial number on the machine identification plate. 2. If the serial number falls within 189442634 - 190001700, **stop using the machine immediately**. 3. Take it to an authorized Stihl dealer for a **free flywheel replacement**. 4. Contact Stihl Inc. at (800) 233-4729 or email stihlrecall@stihl.us with questions. ## Hazard Severity is rated **critical** because: - Flywheel failure during operation projects fragments at engine RPM (a TS 410/420 wheel runs at >9,000 RPM unloaded). - Owners cannot self-detect the defect. - Cut-off machines are typically used in worksite environments with bystanders. This severity calibration is consistent with TNB02600081 (Stihl MS 391 chainsaw flywheel-crack projectile hazard, also a flywheel-failure projectile defect rated warning - but TS 410/420 affects more units across construction worksite use, justifying the upgrade to critical). ## Related bulletins The TS 440 cut-off machine recall (TNB02600112) covers a separate but related defect on a related Stihl cut-off machine model. The TS 480i / TS 500i recall (TNB02600111) covers a fuel-line crack defect on the larger injection-equipped cut-off machines. ## Source - Stihl TS 410 and TS 420 recall page: https://www.stihlusa.com/safety/recalls/ts-410-and-420 - Stihl press release, June 2021