Kohler 4620 toilet
 

The part of the rubber gasket/washer combination that is between the tank and the commode may be too thin; causing the tube type part of the gasket/washer that goes around the bolts to bulge out and rip when the nuts are tightened. It may be possible to avoid this by adding a thick rubber washer or washers to the bolts in the area between the existing gasket/washer and the commode. This would prevent the rubber that goes around the bolts from having too much room and bulge and rip.