What's this wire for? How to fix? 91k100rs

[WHITE91K100RS]

hey brick heads,

I recently changed the battery on my 4v 1991 BMW K100rs and noticed this wire broke off from one end of the connector on the throttle side of the bike. The wires are green/yellow and gree/red (see attached pic)

What's this for and how do I repaire/replace it? I have a suspicion its for the ABS...

[Laitch]

What are your reasons for suspecting an ABS connection?

[The Mighty Gryphon]

On my schematic, green/red and green/yellow go to the sidestand switch.  That broken wire should prevent the bike from running since it will make the motronic think the sidestand is down.  The connector in the photo is not an original, so the wires may have been added and run somewhere else. 



 

[WHITE91K100RS]

Ok, so a bit more info -

I was out riding the bike and everything was working as usual. Went to start th bike after dinner and Battery was dead -'voltage was so low so I had to bump start to get home. Bike was at such low voltage that, when I hit the starter that I could hear the fuel pump barely turning. So, I bought a new battery figuring that would be easy fix. Well, while replacing the battery I noticed that green/yellow wire broken off from the plastic clip I pictured above.

After installing new battery, When I hit the ignition the engine turns but bike doesn't fire. When I turn the key, I don't hear fuel pump buzzing as it normally does. Checked fuse F4 which is fuel pump and sure as could be - fuse F4 was blown! Figuring that would be an easy fix of the fuel pump - I replaced the 15v fuse tried to fire it again, but still nothing.


While troubleshooting, I did confirmethe relay for the fuel pump is clicking own and close when I turn the key, so the issue is not there. I took the tank off and tried to bench test the fuel pump with 12v at the 4pin connector - but the pump didn't make a sound. So, I the my fuel pump may be burnt.... Not yet certain though

But aside from the fuel pump gremlin I'm trying to figure out, I noticed this broken wire that snapped from the plastic connector piece on the throttle side of the bike. I don't believe that is causing my no start problem, but I still want to fix it. Anyone know what that connector is for?

Thanks for your help!


 Bike wouldn't

[Inge K.]

The connector in the photo is not an original, so the wires may have been added and run somewhere else.   

+1 on sidestand switch connector.............but the connector is indeed a original part.

[Laitch]

Did you read Gryph's post above yours, Whit?

[Inge K.]

The sidestand switch cuts the power to the fuel pump relay coil.

[Laitch]

A wiring diagram for your bike is available in the MOTOBRICK.com Technical Library card catalog. That's where this came from.

[Inge K.]

I think you need to test your fuel pump one more time.....
Green/white wire +, brown wire -.

Checked fuse F4 which is fuel pump and sure as could be - fuse F4 was blown! Figuring that would be an easy fix of the fuel pump - I replaced the 15v fuse tried to fire it again, but still nothing.

Fuse 4 is for the power socket, fuel pump fuse is #6.

[WHITE91K100RS]

Ok, so I'm hope that cut wire was the culprit for my fuel pump not turning and bike not starting.

I'm more than happy to  disable side stand kill switch for the sake of fixing the bike. I cut the piece off that snapped (see pictured) and connected each wire directly to the female connector. Think this will work?

I have to pick up my tank before I can test. Won't be until tomorrow...

[Inge K.]

I'm more than happy to  disable side stand kill switch for the sake of fixing the bike.

A better idea would be to change out the connector to another waterproof two pole connector.....
Then you don't have to regret the disabling of the switch, when you lay at the hospital after trying
a left hand turn with the sidestand down.


You missing a rubber between the battery bracket and the expansion tank, part # 61 21 1 459 087.

[WHITE91K100RS]

Good eye, thanks inge! I'll see if I can find a 2 pole connector replacement.

I'll plug my tank in and give this a shot and post back

[WHITE91K100RS]

I cut the connector piece off entirely, connected the cables and covered them. Fuel pump works no problem.. It was indeed the side stand kill switch. Thanks for your help guys!

[Laitch]

 :2thumbup:
Careful on the left turns.  :giggles

[The Mighty Gryphon]

First thing Monday, go and get a pair of the pink(or red) insulated male and female 1/4" flat spade connectors for #18-#22 wire and install them to make a proper connection to the sidestand switch.  Put a female connector on the green/yellow of the main harness, and the male on the other wire coming from the harness.  This should prevent the 12V from shorting to ground in the event the connectors come apart with the power on.  (Inge, please confirm)

Please do this as soon as possible.  We hate to lose members here.

[Inge K.]

Put a female connector on the green/yellow of the main harness, and the male on the other wire coming from the harness.  This should prevent the 12V from shorting to ground in the event the connectors come apart with the power on.  (Inge, please confirm)

 :2thumbup:

Please do this as soon as possible.  We hate to lose members here.

 :2thumbup: The sidestand is easily forgotten when you're in a hurry........I did spend almost 3 weeks at the hospital because of just that.

[The Mighty Gryphon]

When I stop I put the sidestand down so I can dismount, then I put the bike up on the centerstand.  I don't always remember to put up the sidestand, and occasionally I will try to take off with it down.  Fortunately, the interlock and the auto retract with the clutch saves the day.  Probably have saved me from at least 5-6 mishaps in the past 20,000 miles.

It's odd, that I never had this problem with my old bikes.  Probably because they were infinitely lighter and lower I could safely put the stand up before mounting.  With the top heavy weight of the K bike I like to leave the stand down until I am fully seated on the bike, something I learned very early on when I dropped it in the driveway(on a fresh paint job) the fourth or fifth time I took it out. 

[WHITE91K100RS]

all fixed, thanks for your input brickheads   

bought a 2-poled electrical connector for $2 - soldered the wires, wrapped in heat-shrink plastic - problem solved.

I ended up tucking the soldered connections into the harness after taking that last photo. Im also buying a bump stop later today, thanks for catching that Inge!  :clap: