The Honda Owners Club

I currently have a problem with the ingition system on my HONDA CB TWO FIFTY NIGHTHAWK 1992 Model. In June 2009 i had a fault develop with the ignition system which took out the CDI unit. Fortunatly i had a known good unit to replace the faulty one. this has given servicve until last week which has resulted in the second unit failing. any HOC members have this sort of problem themselves, if so what was the solution. i am reluctant to put in another unit until i find the cause of the fault.