My bike is a 1978 R100/7. Recently one of the relays audibly clicks and continues clicking 3-5 times when I turn the ignition on (not started)....just when ignition is on and lights power up. Sometimes the headlight dims a little too and then the clicking stops. It starts and runs fine. Would this be a fault in the headlight relay? I recently replaced the starter relay and horn relay. Is the headlight relay in the bucket? Should I even worry about this?
Only if you like walking home. It's always best to work on "indications" of a fault in your shop at home, rather than be forced to respond to a full-fledged "failure" 200 miles from home.
The headlamp relay is indeed inside the headlamp shell. There is nothing special about the one BMW uses. Most any headlamp relay small enough to fit the space will work.
Additionally, if you have the disc brake master cyl under the tank, then it is best to remove the tank and check for electrical contact corrosion caused by leaking brake fluid. Any brake fluid leaks should be repaired and new brake fluid installed.