O.S. Engine OS21532120 Crankshaft OS Speed 12TZ Spec-2  [OS21532120]

Crankshaft for OS Speed 12TZ

This crankshaft is an OEM-design replacement part for RC-scale nitro engines identified as OS Speed 12TZ Spec-2, intended for direct engine rebuilds and maintenance. It serves as the rotating core inside the engine case, providing the counterweight and journal surfaces required to convert piston motion into rotational output within a model engine.

Use this part when performing a mid- or full-engine teardown, paying attention to bearing condition and seal surfaces during assembly. Proper cleaning of mating surfaces and careful inspection of the crank journals and counterweight balance help maintain engine smoothness and longevity. This description treats the item strictly as an RC accessory for the indicated OS Speed 12TZ line.

The part plays a tuning and reliability role: replacing a worn or damaged crankshaft can restore mechanical timing consistency and reduce vibration that affects idle stability and throttle response in model applications.

Choose this crankshaft when you need a direct replacement for an OS Speed 12TZ Spec-2 engine during maintenance or rebuilds, and verify bearings and seals as part of the installation process.