Fitting Electronics? Take note. it could save you money.
I have had to trace a fault on my Enfield. The starter solenoid had failed. In checking out various readings I discovered that when the starter solenoid switches off, the collapsing magnetic field induces over 25 volts across the battery, and everything connected to it. (This voltage is just a momentary spike).
I would suggest that you never leave a phone, GPS etc. connected to the bikes power when you operate the starter motor.
PS, do not pressure wash Enfield starter solenoids either