I have successfully sealed an oil leak caused by a crash, then rode it about 800 miles back home without problems. The product that I used is named Seal All. I cleaned the crack with carb gum cutter at a service station, dried it with a paper towel and applied the Seal All as directed by the station jockey who told me about the stuff. Once it dried it held just fine even though it was bathed in hot oil the whole time. I was riding an airhead R90 BMW  and crashed the valve cover into a rock and cracked it. I'd say that the valve cover gets at least as warm as a HD case does and has a pretty good amount of oil in it. If you follow Cottons procedure and use this product I think you might have a good outcome. If it doesn't, you've only lost a little time. Good luck.