Manic Mike

Can anyone help I have a 1988 FZR 1000 Genesis. It has developed an ignition fault that seems to have fried two CDI units. Sympyons = It started - went onto two pots - then no spark - then two pots again - then no spark again. Replaced the CDI and it ran great for about 5 miles and then the above symptons happened. I have changed the coils checked all continuity etc etc but I cannot sort the fault. I have ordered another CDI but do not want to put it on and fry this one ....... it starts to be expensive. Thanks