your observation of a weak spark may not be connected to the OVP, possibly the OVP has a cold solder joint at the junction of the zener diode ,while the fuse is still good. this will give cold start problems.
A fresh rotor ,cap and leads will set a good base for checking and likely solve the weal spark and starting problem.
A warm cis engine should run in Basic mode even with the OVP or the EHA disconnected .
mak

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mark