My daughter was riding her dirt bike last weak. When we tried to start it this week it wouldn't start. I pulled the plug turned it over and no spark. I checked the coil and had 5 ohm primary and 12k through the secondary so considered it ok. I checked the shut off button and it checked out ok. I then decided to check the plug again... I found a tiny spark from the center electrode to the engine fin. But not strong enough to spark to the side electrode??? Any ideas?