When you went to the electronic ignition did you also go to a new voltage regulator. The old regulators would charge the battery to approx. 12.5 volts whereas the new ignition systems need that battery charged to 13.5-14 volts and the new regulators will do that. You may also have a slow draw on the battery and after sitting overnight the voltage has dropped 1 or 2 and ignition won't fire hot enough to start the engine. What I'd suggest is check the voltage of the battery, at the battery, after it's been sitting for 24 hrs then put a charger on it and see if it'll start or better yet boost it with a running engines battery.
Terry