That is really frustrating but you are in good hands in this forum. I know from personal experience with my bike being down for a summer and trying to troubleshoot it. There are lots of experts here that know the KLR inside and out. In general people suggest starting making sure the fuel, spark, air, and compression are working properly to systematically diagnose the problem. I’ve linked a post with the way I tried to move though the diagnosis process, including my first compression check. Your bike sounds different than mine did so hopefully a more simple fix. KLR650 turns over but doesn’t start