My recently purchased 1986 K100RS appears to have an alarm (under the seat) with a key-lock apparatus forward of the alarm position on the left side of the bike.  I have a key that fits the key-lock but to this point don't know how to make the alarm function (arm/disarm).  Any information on the function and trouble shooting the alarm would be much appreciated.  I am attaching photos of the alarm unit and the key-lock, that I think operates it.

There's a 9 volt battery inside of the alarm that probably needs replacing.  To arm the alarm just turn the key.  To see if it works, open the seat.  The horn should sound.  I can't remember if any of the lights flash.

There are pictures and labels of the works in this thread. Printed instructions are still elusive.

There's nothing extraordinary about this alarm system.  Turn the key 90 degrees and remove it.  I believe that you you remove the key in the horizontal position.  It's armed.  To see if it still works just open the seat.  When I go to my second home later this month I can see exactly what position the key should be in for it to be armed if you haven't got it working by then.  Make sure the 9 volt battery I mentioned earlier is good.

I browsed the thread mentioned above and I believe that the one on my 91 LT maybe a newer version.  While the black box looks the same, I know mine has a replaceable 9 volt battery.  There is a small cover that can be removed to replace it.  The one in the thread mentioned above appears to have a 4.8 volt rechargeable battery.

I opened the lid on my bike alarm and see what appears to be a 4.8 volt battery.  The battery appears to be affixed to the board with glue (see pic).  If any of you pros has experience with these batteries, I would appreciate any and all suggestions on recharging or replacement.

Is there a milliamp rating on the battery?  I found this battery on ebay.

http://www.ebay.com/itm/Varta-4-CP300H-4-8-Volt-300mAh-NiMH-Battery-with-Tabs-FAST-USA-SHIP-/231628407579?hash=item35ee21031b:g:7noAAOSw9N1VrXJm

Clean up that mess with a soft toothbrush and electronic cleaner like DeoxIT, Larry, and you might discover that kioolt has found a battery for you.

Thanks guys.  My battery (Varta) shows 4.8V and 22.5MA.  The thread above indicates a 12v charging port on the board (red).  Does anyone know if I can recharge the battery through this port?

looks like a stack of rechargeable NiCad type batteries ...likely is 4 x sub aaa  or  "n" type    hearing aid type size batteries  can be usually found in 3 x in older computer backup memory types ,  but 4 x is likely in this case , found to be shrink wrapped to form a package .  (4 x 1.2 volts ( nicads ) =4.8 volts
I have a thought that a lot of older portable home phones use this type and size  so should be easy to find
usually there is a charge circuit inbuilt to the alarm system that would normally keep them at float charge whilst connected to the system

the real issue is with nicads that one of the cells will go high resistance ...ie will show charged when unloaded but on load will drop dead

you should be able to find suitable replacements at any "battery repacking" type business these days

my guess would be under $20   or about there ... then to reattach them to the pc board .  a hot glue gun is usually used for such things ?


good luck , doesn't look too hard at all

I've got this device on my '86 K75c and it didn't work because the original NiCad was defunct, once I got the mega-tight Tri-Wing screws out of the top it was a simple job to replace the cell with a similarly rated NiMh pack ( 4.8v 255mah I think it was) obtained from an electronics supplier ( RS Supplies here in UK ) When refitted it all worked just as the K75 Rider's Handbook said it should.

 Is that small socket for charging or for some sort of 'bridging pin' to prevent discharge when the unit is removed from the harness? I've tried several times to find info on this unit using the BMW codes embossed on its lid but all to no avail. I guess an electronics expert could work out the circuit by looking at the board.

Kando wrote:Is that small socket for charging or for some sort of 'bridging pin' to prevent discharge when the unit is removed from the harness? 

According to the photo found in the link in post #3 of this thread, it's for charging.

Thanks for giving me a nudge to look back to the start of the thread and post#3.