K11 Owners Group

[TravelerJim]

Well, bloody hell.

Out running some errands this afternoon, and my K1100LT decides to have a problem starting after my next-to-last stop. But does, so up just a couple blocks to my last stop. I come back out, and the bike won't start at all. Starter barley spins - and hey, what's that black smoke coming out from under the seat?

Park, pull it open, and I find that the little standalone wire (ground, I'm guessing?) from the battery to a flat terminal on the outside of the ECU is totally fried. Insulation is nearly gone, broken in two places, and what's left is so brittle it nearly falls apart when I touch it. Must have shorted on something, because it was trying to burn a hole in the plastic reservoir. Didn't manage to, but there's a nice black scorch mark on the reservoir now.

My best guess is that the insulation was worn and was shorting on some metal bit or other nearby.

Given that I've only had the bike two weeks I have to ask - is this a common problem?
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95 K1100LT
02 CalSS

[Moondog]

I can't personally answer that but I would inspect the rest of the wiring on the bike now. Never know who was the last person was who touched it and what they knew.

[Scott_Anderson]

I'd look at the underside of the ECU, where the battery is, just to make sure that there is no contact with the + battery post.
The OEM BMW batteries have a hard plastic cover that insulates the battery posts from contacting the underside of the Motronic ECU case. Other brands of batteries don't have those covers, and if you are not careful when istalling, you can have problems, or cause problems in the future.

That little black wire is supposed to be the ground point for the ECU case, as the rest of the case mounted on rubber for vibration isolation.
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Ride safe.



1995 K1100LT 0302044
2017 FLHTK Ultra Limited
Garmin StreetPilot 2820
Garmin Zumo 550
Garmin Zumo XT
"One who does not ask questions is ashamed to learn" Danish proverb
1997 K1100LT 0302488(R.I.P.)
1997 R1100RT ZC62149(sold)

[Fifth Horseman]

Check the main battery earth cable (battery -ve to starter motor body) at both ends for condition and security also check that the battery connectors are not touching the underside of the ECU tray, then check all the cables and clean all the connectors you can find In the absence of the main earth and if the ecu body makes contact with the frame all the current will may to flow through the ECU earth cable and as you have seen its not up to the job.
When I first got my K11, the PO had managed to leave the starter end of the main earth cable loose, then wondered why it wouldn't start - got the bike cheap tho' - just as well with the many other problems I found with it (clutch, leaking forks, front wheel and head bearings, etc) good learning experience but ended up not being a cheap bike after all.
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'99 K11LT

[Ernie-NH]

Good morning all...

The "melted wire" problem is one I had as well, way back when I first got my LT... In searching around for the fault, I found that the ground just in front of the starter was loose and corroded.... meaning that the high starting amperage by the starter was finding its way back to Battery(-) via the easiest path possible and that was through that ECU case to Battery(-) link. It completely melted just as as Jim described.. after cleaning and deoxidizing all grounds, wherever I could locate one, the system has functioned without a flaw for the last five years. I think that since BMW in general has a "fluky" way of routing dependent grounds, Jim should go through everything as I did, learning about the bike and fixing the potential electrical problems before they happen. That little ECU to Battery(-) lead is not in my opinion necessary anyway, since the forward clip of the ECU ( ie: Motronic ) case can be secured to the frame directly. The internals of the ECU are isolated from its case in any event and are thus protected. OK... thats my $.02...

Best regards all......// Ernie in NH
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Airhead Beemers Club
'11 G650gs
'95 K1100LT
'76 R100/7

[TravelerJim]

Yep, that's exactly what happened. New ground wire, problem fixed.

Well, that one anyway. The root cause is that the bike has an Odyssey battery, and a "custom" insulating shield between it and the ECU which is what failed.

Local BMW dealer wanted ~$170 for the "correct" BMW battery, and another $80 to install it. Really? $80 to install a battery? Wow.

I'm passing on that, the Odyssey is in great condition otherwise. I just need to fab a better insulator. Anyone done this before and have some tips on what they used?
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95 K1100LT
02 CalSS

[blue95lt]

Jim,hi I'm Keith,I put a floor board on top of batt.
One of the modern day,very thin ones . Hope u have some luck! Keith
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1995 k1100lt daily ride(22953)when I got it
1982 cb650sc blue nighthawk (38000)(crashed)
1974 kz400(sold to get nighthawk)