Buy Kubota KX 121-3 replacement drive sprockets online individually but inspect your entire undercarriage and consider replacing the rubber track and sprocket at the same time to maximize the lifespan of the undercarriage and minimize premature wearing.
This is the replacement aftermarket steel drive sprocket for the Kubota KX 121-3 mini excavator. The overall sprocket diameter is fifteen inches from tooth tip across to the opposite tooth tip when it is brand new with no wearing. There are nine bolt holes in the sprocket to mount to the original travel motor. There are twenty three teeth on the sprocket for precise unique fitment with a specialized rubber track that is specifically designed for the Kubota KX 121-3 and some Kubota KX 040-4. Must verify fit for KX 040-4. It does not interchange with any other manufacturer or model so be sure you are buying from knowledgeable, experienced staff that knows your Kubota KX 121-3. The drive motor mounting hole diameter is eight inches across. The widest part of the sprocket at the base of the tooth is 1 1/2 inches.
Here is the complete line of undercarriage parts for the Kubota KX 121-3 including the rubber track, drive sprocket, bottom rollers, top rollers, and tension idler.