After riding for a couple of hours on the new bike, my son noticed a low pitch squeal when the bike was shifted into 3rd gear or down shifting from 3rd. Is this just part of the breakin process or is this something to be concerned about? The bike is still under warranty. We are fairly new to off road riding.

 

Welcome to KF I am not familiar with the klx 140L. Could be gear whine. Have you gotten the service manual yet on it? Let us know on what you find and congrats on the new ride.