I bought the KZ650 years ago. I knew I would eventually have to fix or replace the engine cases, and of course the cracks were right on the threads which made the repair a little tricky. Well the time had finally come. I was in the middle of rebuilding the motor so I figured, why not now. I bolted the cases together, and removed the JB weld that was previously there. I then preheated the weld area with a propane torch. This was my first real test when it came to welding aluminum, so I was a bit nervous. The beads went in smooth with no real issues. I then ground down the welds and re-tapped the threads for the points cover bolts. I was more than pleased with the results!!