Stop and investigate.
As stated, it is difficult to diagnose a noise, but any unusual noise requires investigation. There are several possibilities : The automatic decompresser device on the exhaust cam shaft, the cam chain tensioner and the balancer chain (doohicky), adjuster. It is no good trying to start it, you will only inflict more damage. The KLR motor is strong, the only weakness is the balancer chain adjuster. If broken and not attended to the damage is horrid !!! Unfortunately if the motor has been the victim of a monkey mechanic then the list could be endless, I would have a look at the doohicky first, but if you can be sure that the upgrade has been done, then remove the cam cover, and have a look, the cam chain and decompresser are easy to check.