Recently my 1987 NSR250 has been having some ignition troubles. The cdi for the rear cylinder stops working within a 10-15 mile ride. I've gone through three now for the rear cylinder. Other cdi has been fine ever since I bought the bike. I'm officially stumped. Not sure if the cdi fries somehow or what. Could there be bad wiring leading up to the cdi? Maybe a bad resistor? I'm tempted to take the cdi in to a computer repair shop. I really don't want to go through the harness but it's looking like I may have to. Anyone familiar with how or why a cdi fails or fries?

Swap CDI units over see if problem moves to other cylinder. The CDI's suffer with dry solder joints and can be repaired in many cases.