Hi, the Bosch CDI's are, in some cases, are more than 50 years old and typically will die at some point. But I get exactly what you are saying about not spending $ unless necessary. The majority of the units I service are dead, but I do also get the occasional one that is still alive and kicking. The problem with the earlier units, ('69 thru '71) is that they had a power component poorly mounted and so that device (voltage regulator diode) blows out from overheating and then the unit runs at about 100V over it's intended operating voltage of ~400V. This stresses other components and eventually wipes those out. That being said, I've seen plenty of them operating at 500V and not dead yet, so you never know when that is going to happen. When I rebuild these early units, I modify the mounting of the power components to eliminate this problem and I always upgrade the discharge capacitor as the original one will eventually fail. (accounts for a good 75% of the failures I see). For now, I can provide some simple troubleshooting/bench test instructions if you simply want to see if the unit is operating and then decide from there if you want to move forward with having it rebuilt. Just email me,
bob@ashlocktech.com --Bob