To tighten the tracks chain track link on a cat excavator, you can follow these general steps:

Park the excavator on a level surface and engage the parking brake to ensure it is stable.

Locate the track tensioning device on the excavator. It is typically located on the front or rear side of the track frame and consists of an idler wheel or a cylinder with a tensioning spring.

Use a wrench or socket to loosen the lock nut on the tensioning device. This nut secures the adjusting bolt in place.

Turn the adjusting bolt clockwise to tighten the track tension. This will increase the tension on the track chain.

Check the tension of the track by pushing on it at the middle point between the drive sprocket and the front idler. It should have a slight amount of give, but not be too loose or too tight. The appropriate tension can vary depending on the specific model of the excavator, so consult the manufacturer's guidelines or an experienced operator for the recommended tension.

Once you have adjusted the tension, hold the adjusting bolt in place and tighten the lock nut to secure the adjustment.

Repeat the process for the opposite side of the excavator.

After adjusting the track tension on both sides, test the machine by operating it in forward and reverse and observing the tracks. They should move smoothly, without excessive slack or binding.

It's important to note that these steps are a general guideline, and the specific procedure may vary depending on the model and type of Caterpillar excavator you're working with. Always refer to the operator's manual for the correct instructions and consult with a trained technician or the manufacturer if you're unsure about any aspect of the track adjustment process.