I did basically the same thing when I toasted the clutch in my KLX300, except I poured diesel fuel through the motor and clutch area and then WD40, then filled it with motor oil and started it , warmed it up, then drained the oil 3 times before actually riding the bike. I believe the XR400 has an oil screen in the frame downtube you need to check for debris or you could burn up the motor. What conditions were you riding in when you burned up the new clutch? Did you have enough freeplay in the clutch cable? You have to pay close attention at all times, but you really need to pay real close attention to the freeplay on a new clutch the first few miles until it breaks in. I would put the HD springs in with the old plates or you might toast it again.
Good luck and Check that freeplay :)