high/erratic idle on 83 R100RS
Some time back I was struggling to resolve a puzzle. My 83 R100RS' idle climbed when it was warmed up. Long story short, I was convinced it was something related to the carburettors or their cables. Nope. It was the digital Ignition Control Unit that I had "upgraded" with an after market replacement. I contacted the merchant, described the symptoms and he immediately agreed to send me a replacement without charge. He stood behind his product, consistent with the sterling reputation he enjoys within the rider community.
In the course of my trouble shooting this mystery, I've uncovered another issue with the bike: a problem somewhere in the wiring loom causes a current draw (2.25 Mv) even when the ignition switch is off.
Electrickery, my favorite challenge!
How much would the clock draw?
Did you mean "2.25 mA" - "A" as in "amperes"? If that's so it would draw (2.25 mA * 1,000 hours) = 2.25 Ah in 41 days or roughly it would drain your battery in a year if not used at all.
I have never measured the current of such analog clocks but that could be it.
You're correct, Guenther. I should have stated 2.25 +/- milliamps. However, I'm not sure that level of current drain is as insignificant as you might suggest. When my efforts to solve the problem of poor running on my R100RS failed, I put the bike in the corner and tried to forget it. It sat for 8-10 weeks (clock was not connected). When I installed the new ignition module this week, the new battery was not able to even illuminate the instrument lights.
I feared I had ruined the new battery due to the current drain. I connected it to my charger and after about 40 hrs. it held 12.5 v. and was able to start and run the bike. I disconnected the earth cable and after one day the battery still shows about 12.5 v.
I hope I've dodged a bullet here.
How reliable is your ampmeter?
Was the battery well charged when you did the test?
Did you measure the current between the bare minus pole of the battery and a ground point where the ground wire is connected to the transmission?
What are the amp hours (Ah) of your battery?
I am just curious because I doubt that the clock could have drained the full battery in that short time.