RD118-21300 Kubota 121-3 Mini Excavator Idler

New undercarriage parts and rubber tracks are sold individually but we suggest replacing all of your worn parts at the same time.

This is the aftermarket replacement front tension idler for the following Kubota mini excavators:

KX 121-3
KX 121-3SS
KX 121-3ST
KX 040-4

This idler is a complete assembly with mounting brackets.

The idler must be replaced when significant wear is present to keep the track tensioned properly. If you run on worn idlers the track will lose tension and many other problems will occur such as de-tracking. Keep your track tensioned properly by greasing the tension idler into place and check the tension daily and evaluate the wear on the sprocket and idlers. Uneven wear will result in premature track damage. You will see the best results and longest lifespan of the undercarriage if you maintain the tension and replace wear parts at the same time.

This part is commonly referred to as a tension wheel or tension pulley but it does not come with the actual spring tensioner. The idler comes fully assembled as seen in the picture.

Alternate Part Number:	Kubota dealer part number: RD148-21300, RD138-21300, RD148-21700, RD118-21300
Alternate Model:	The RD118-21300 idler is interchangeable with the KX040-4 and all models listed above.
Alternate Part:	There are no known alternate part listings for the KX121-3 mini excavator, this tension idler is guaranteed to fit.

Kubota KX 121-3 Undercarriage Parts

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.