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1993 K1100LT Running Badly

 
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petewright1972@gmail.com



Joined: 10 Dec 2014
Posts: 15

PostPosted: Sun May 21, 2017 3:26 pm    Post subject: 1993 K1100LT Running Badly Reply with quote

Hi all

My 1993 K1100LT has started to run erratically once it has warmed up. The warmer it gets, the worse it gets, eventually cutting out altogether. It smells rich and pulling the plugs has confirmed this is the case.

I have done quite a lot of research and the common points of failure seem to be the oxygen sensor and the coolant temperature sensor.

Not sure whether my bike (UK police model) has an oxygen sensor - can anybody confirm whether all models have them or whether they are omitted from certain variants? If mine has one, where exactly would it be - I've looked in the most likely area around the exhaust collector ...

With regards to the coolant temperature sensor, I have located this but it's not in the most accessible of locations. Is there any way I can test whether this sensor is working with it in situ?

Further research leads me to believe I can at least check electrical continuity on the circuit for this sensor but which pins would I test on the motronic plug? An indication of how the pins are numbered would also be useful here ...

Of course, my research only indicates that these sensors are the most likely culprits but if anyone has any further ideas, I would be grateful to hear them.

Thanks in advance
Pete (Devon, UK)
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Scott_Anderson
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Joined: 05 Sep 2006
Posts: 3117
Location: Central Iowa, USA

PostPosted: Sun May 21, 2017 7:00 pm    Post subject: Reply with quote

This image(thanks Shogs) may help with location, IF your bike even has one.....


Generally the O2 sensor and motronic control REPLACED the older mixture potentiometer setup that was in the airbox on the Jetronic control systems.

The air temp sensor would also have an effect on your air/fuel mixture as well.

The water temp sensor input is landed in Terminal #2 of the motronic plug
The air temp sensor input is landed in Terminal #22 of the motronic plug
As far as the O2 sensor, it will have +12 input for the heating element(powered from the fuel pump relay). 2 ground wires, and a mv output to the motronic terminal #24

You may need a magnifying glass, but the end terminal #s are marked on the connector. I don't recall at the moment which end the numbering starts from.

Another item to investigate would be the Hall sensors, they have a history of causing a bike to cut out and die when warmed up.
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Ride safe.



1995 K1100LT 0302044
1997 R1100RT ZC62149
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.)
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Flying Duck
PsyKotic Waterfowl


Joined: 27 Jan 2005
Posts: 10082
Location: Bumf***, WA

PostPosted: Tue May 30, 2017 9:15 pm    Post subject: Reply with quote

1993s have an ignition amp that attaches to the front left of the battery tray. When the heat sink compound between the ignition amp and the battery tray deteriorates over time the ignition amp gets too hot and causes the bike to run poorly when things warm up.

Solution: Go to a local electronics store and buy a small tube of heat sink compound. Take the ignition amp off of the front of the battery tray and thoroughly clean off all of the old heat sink compound. (Use steel wool or a wire brush.) Put a nice healthy dose of fresh heat sink compound on the back of the ignition amp and reassemble.

Note that this only applies to the early K1100s (and K100RS4Vs/K1s) as the 94+ bikes have a slightly different ignition system and do not utilize an ignition amp.

There is a very good chance this will resolve your issue (I've seen this a few times before) but even if it doesn't it is inexpensive, easy to do and good preventative maintenance.


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93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
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petewright1972@gmail.com



Joined: 10 Dec 2014
Posts: 15

PostPosted: Mon Jul 03, 2017 12:33 pm    Post subject: The Brick Flies Again! Reply with quote

Firstly, thank you to everyone who replied to this thread - and to all those posters to earlier threads on the same topic.

Happy to say the problem is resolved!!!

Soooo ... what did I try - based on feedback and earlier threads?

The Engine Coolant Temperature Sensor was fine.
As was air temperature sensor.
There was no o2 sensor to test.
Hall sensor was fine.
As was TPS.
Continuity tests on circuits to all sensors showed no circuit breaks.
All pins etc cleaned on Motronic unit.
Ignition amp cleaned and re-heat synced.
Plugs and HT leads checked fine.
etc etc etc
Was fast running out of ideas and suggestions Confused.

Then, whilst putting everything back together one time, my friend but a different fuel tank on and .... yep, purring perfectly. Switched back to original tank - started breaking down again as soon as the engine warmed up. So we'd essentially narrowed it down to either fuel pump or fuel filter.

Next (easiest) step - removed the filter from the original tank. Perfect! New filter ordered and installed and Bob's yer uncle!

So - please forgive my naivety, and maybe humour me with some more answers. Just to feed my curiosity you understand ...

Why would a faulty fuel filter cause the bike to start struggling once it has warmed up? My understanding is that the engine needs more fuel when it is cold - which is why it runs richer until Motronic gets a signal from the coolant temperature sensor saying its warmed up. So if the filter is clogged, it should surely struggle when cold (not enough fuel getting through) but be better once its got up to optimum temperature.

Or is my understanding and limited logic flawed?


Thanks
Pete (1993 K1100LT - Devon, UK)
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Flying Duck
PsyKotic Waterfowl


Joined: 27 Jan 2005
Posts: 10082
Location: Bumf***, WA

PostPosted: Mon Jul 03, 2017 5:54 pm    Post subject: Reply with quote

It might be that whatever is clogging your fuel filter expands when the tank warms up and the gas does as well.
_________________
93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE
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Al.
Flying Brick Rider


Joined: 28 Oct 2005
Posts: 383
Location: West of Ireland

PostPosted: Mon Jul 03, 2017 6:48 pm    Post subject: Reply with quote

Had that problem. It started when I hit a bump.
It struggled for a short while then was fine.
On journey home it stopped. I pushed it off the road and then it started
and I drove home.
I cannot remember how I figured problem or how long more I
drove before having to change filter.
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1994 K1100 LTSE + Blackbird
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petewright1972@gmail.com



Joined: 10 Dec 2014
Posts: 15

PostPosted: Tue Jul 04, 2017 5:34 pm    Post subject: Reply with quote

Ah yes, Flying Duck that makes perfect (even if not obvious until pointed out) sense - thank you!
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Grunter
Flying Brick Rider


Joined: 30 Sep 2015
Posts: 367
Location: North East England

PostPosted: Thu Jul 06, 2017 2:48 pm    Post subject: Fuel filter shot Reply with quote

If the fuel filter is unfortunate to suck in a bit of water that has somehow got into the tank, the filter will fail very shortly afterwards. (We probably have more rain over this side of the pond). Confused
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1994 R1100RS
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