Either cracks, or dirt paths that would let the juice travel from the center wire to the plug wires. Often the cause of misfires on distributor type ignitions.
Tim Crump AMA#664988 MGNOC #262 FSSNOC #3057 AMF#100239 98 Moto Guzzi V10 (1000) Centauro 69 Moto Guzzi 750 Ambassador 80 Moto Guzzi 500 V50 II 98 KTM 620 Rallye Adventure "Remember, traffic lights timed for 35, are also timed for 70 mph!!" http://msnhomepages.talkcity.com/YosemiteDr/guzzitim/GUZZITIM.html
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