Z1OwnersClub GB

hi all
took the a4 out today for a spin and broke down but managed to limp home on two cylinders.
took the tank off and both dyna coils are badly cracked, the left hand one that feeds 1 and 4 failed.
any one know what causes these coils to crack like this ?
never smelt them getting hot previously on long runs

Usual reason for cracking is using the stock coil mounting posts which are slightly too short .
This causes the body of the coil to hit the frame before the steel core sits fully on the mounts which results in the core bowing as it's tightened down and eventually the coil insulation cracks.
Most of the time the actual cracking isn't an issue but once moisture gets in corrosion will eventually kill them.
Catching it early by sealing the cracks with nail varnish or similar and fitting longer posts or a couple of washers to space the coils away from the frame usually saves them.
If the coils are very old though the insulation just cracks with old age and heat cycling even if mounted correctly.

thanks Rob
did notice the plastic was touching the frame when I fitted new ones so spaced them with washers
all good to go again