What is this under the tank R90/6

[focusrsh]

Quick (and probably dumb) question . What is this black box with a red top under the tank of a 1974 R90/6.
Looks like something electric, but I don' want to start prying/pulling to take a look.

[gsm_r100rt]

Voltage Regulator. BMW Part # 12 32 1 244 409

[Rob Frankham]

Yes, absolutely the voltage regulator... not the original but a BMW replacement part. The original would have been a metal can about 3 times as high as this unit and would be a mechanical regulator. This one is electronic and a little more efficient. The voltage regulator controls the output from the alternator and the charging of the battery by preventing line voltage from exceeding 14 volts when the engine is running. If you are experiencing charging problems with your bike, this might be the culprit although there are a number of other possible causes.

Rob

[focusrsh]

Thank you. I won't mess with it