removed the rear plug and It snapped In half....Are H.D pluggs normally that delicate??....also while the tank was off....there was a electrical block behind the carb that's not connected to anythting...whats that for????

 

The insulator on most spark plugs is made out of aluminum oxide ceramic, and it doesn't take too much 'sideways' pressure on a plug for it to snap.

It's not all that uncommon for a deep socket to not be centered correctly over a plug, resulting in sideways pressure on the insulator, which could cause it to break.

Harley sparkplugs are made by Champion, and are no more delicate than any other plug that has a ceramic insulator.