BMW K bikes (Bricks)

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Jhepburn

Jhepburn
Silver member
Silver member
We have two 84/85 K100RS - mine, which is daily usage, and my partner's. The second one has been used intermittently, and has now been replaced by an F650GS which is enormous amounts of fun and a better weight for her until F800s drop in price. The second K will be on the market soon - we hope.

The second K had a completely dead battery last time we went to use it. It hadn't spent too long sitting, so we were a bit annoyed about that. There seemed to be a short within the battery, so there was no hope of recovery.

Today, I put my good battery in bike 2 to get it running and check everything.

When I put the second terminal back on, there was a crackle, spark, and the starter motor started up. Apparently, my reactions are quite good.

I triple checked the ignition was off.

Clearly, I'm going to have to do a lot more trouble-shooting than I was hoping for.

Whiel I take a deep breath before pulling things apart, anyone have an idea what the most likely place for a short would be?

    

Kyle10

Kyle10
Life time member
Life time member
Starter relay, my guess. Fusing via a weak charge. 

Battery new or old one recharged?


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1985 K100rt 0052183
1983 Honda VF750 007713 
    

RicK G

RicK G
VIP
VIP
The best place and most likely place is the starter relay in the relay box under the rear of the tank.
The contacts have a bad habit of welding themselves together when in a dead or almost dead battery situation.
The relay is in the back right of the relay box and can be easily removed and opened with a small screwdriver to pries the plastic case off, you may be able to pries the contacts apart and clean them with a bit of 240 wet/dry sandpaper which will keep it working. There are 2 contacts and both need to be in good condition for it to work correctly.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

Jhepburn

Jhepburn
Silver member
Silver member
Ha ha, just found this: http://www.k100-forum.com/t724-starter-motor-fault

Am sallying forth to have a look at the relay right now.

    

92KK 84WW Olaf

92KK 84WW Olaf
Life time member
Life time member
Its an easy fix and if its done in a used one from Motorworks or Motobins is cheap enough. Is easy to fit.


__________________________________________________
1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 100,380 miles
1983 K100RS 0011171 Fricka 606 29,495 miles Damn K Pox Its a Bat outta Hell No 33,600 miles
    

Jhepburn

Jhepburn
Silver member
Silver member
Oh, I love it when a problem is simple. The difficult part was pulling off the fuel lines to remove the tank.

The starter relay contacts were separated when I pulled it apart, but that must have been from my handling it. The contacts were corroded. One was mostly gone, so there's only a small, angled contact. I had to put it back in to check it. I found that an emery board cleaned them admirably.

The bike works so beautifully that with the tank off, a tap on the starter button was enough to make it run and idle for a second just on vapours.

It's possible that wasn't the smartest move, but it was satisfying as hell.

Thanks for the quick response, Rick and Kyle.

I'll be replacing that relay before we sell the bike.

BTW: The battery I put in was out of my bike, so it at least was the known good quantity.
 
[Edited for spelling]

    

Kyle10

Kyle10
Life time member
Life time member
Sweet! Doncha just love it when it's an easy fix? 

Btw, if you replace the relay use a genuine OEM one. I went thru two Brazilian ones before buying a BMW relay and have had no prob's since.


__________________________________________________
1985 K100rt 0052183
1983 Honda VF750 007713 
    

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