Copper Washer under Spark Plug

K Model heads crack.  Most heads I see are cracked.  A common place for cracks is up the spark plug threads, then across the flat surface of the head, going away from the spark plug.  I noticed a crack near my rear spark plug.  Wiley suggested a wide, large OD copper washer under the spark plug, covering the crack.  I found a washer at Car Quest.  Cleaned the crack with some electrical cleaner, a bit of sealer on the crack.  Removed my current spark plug sealing washer, and replaced it with the copper washer . . . tightened it all down - and now I have full compression again (7:1) in the rear cylinder, and no leak.  I can now keep riding in this great November weather we are having.  Sunny and 65 !  Then Sunny and 55 . . . then Sunny and 45 . . . then cloudy and 35 . . . then cloudy and 25, then 15, then 5, then -5 . . . then "this sucks . . ."