need help with ignition coil module on 1980 R7070

i have a 1980 2 stroke 21" push Lawn Boy which i love...problem is that i can't seem to keep it alive!! i have replace the ignition coil 3 times in last year, once with the high dollar original style from Lawn Boy dealer, and 2 times with Ebay Taiwan replica....the one from the dealer lasted half of a season, the others lasted about TEN MINUTES!! can someone tell me if this is indicative of the new coils or am i possibly doing something wrong with installation?? this is getting EXPENSIVE! thanks for any help you can offer. Rick