Oil Question 1500 Vulcan

[seeing]

I just bought a 01 1500 which had a cracked oil case where the guy ran over maybe a speed bump and came down hard. I cleaned the case sealed it with JB Weld all was good till I changed oil. Not sure but think he was using 20W50 mobile one. I changed to synthetic 10W40 on advice of motor cycle shop. No leaks before but now have some that appear hours after parking the bike from a ride. So I re-did crank case with JB Weld not sure that is where it was leaking with marine JB Weld which seals better from any oil leak. Again not sure where the leak is from just guessing. Now I also put new filter on so can I change back to regular 20W50 if leak continues and use new filter by draining the new one of synthetic oil ? Less than 100 miles with new filter. Also where is the screen that every one says clean on this bike ? Thanks to all.