K1100LT running on 2 cylinders only - with a twist.

[BlueK11LT]

Hi,
When accelerating past 60mph today my 1997 K1100LT lost power suddenly so I brought it to a stop and realised it was only running on two cylinders,i managed to nurse it the short distance home,and after letting it cool down for a while I started it up again for a few seconds and found that only the exhaust headers for no2 and 3 cylinders were getting hot,so obviously 1 and 4 are not firing.
The strange thing about it is (well to me at least) is that the tachometer has stopped working at the same time,so am I right in assuming that the tacho and the ignition circuit for 1&4 share a common electrical component/power feed etc and this is where I should be looking for the fault?
Thanks.

[Martin]

Hall effect trigger one controls 1 & 4 the other controls 2 & 3. Front coil controls cylinders 1 & 4 rear coil cylinders 2 & 3. So you have 2 possibilities.
Regards Martin.

[Laitch]

The most simple approach is to disconnect the plug to the instrument pod, clean it thoroughly, reconnect it then do the same with your motronic control plug. After that doesn't remedy the problems, we'll start sweating.

[BlueK11LT]

Thanks for the replies
where exactly is hall effect trigger one on the K1100LT,what does it do and would the failure of this item also stop the tachometer from working as well as coil for cylinders 1&4 ?
If the plug on the instrument pod was dirty and was stopping the tachometer from working then this wouldn't stop cylinders 1&4 from running though would it?
Both of these two problems have obviously been caused by the same fault in my opinion.
p.s  I did spray electrical contact cleaner spray onto the motronic pins and plug and pushed the plug back in a few times but as expected it made no difference.
Thanks.
Dave

[Martin]

Under the "T" shaped cover at the front of the engine, test procedures are available on this site. The tacho runs off the coil, the coil is told when to fire by the Hall effect sensor. So either could be the problem. You really should have a manual they can be downloaded.
Regards Martin.

[Scott_]

Check around for any chaffed/grounded wires.
The coils are powered hot continuous when the ign key is on and the ground lead is switched on/off by the motronic based upon the input from the hall sensors. (they are nothing really more than a crank position sensor, but there are 2 of them)
The tacho circuit ground wire is connected to the same motronic pin for the cyl 1/4 coils.
If either of the ground lines going to the motronic are skinned/hard grounded then the tach won't work and the cyls won't fire.
You could possibly have a failed coil.

It's hard to say from here, all we can do is offer suggestions for what to check.

[BlueK11LT]

Check around for any chaffed/grounded wires.
The coils are powered hot continuous when the ign key is on and the ground lead is switched on/off by the motronic based upon the input from the hall sensors. (they are nothing really more than a crank position sensor, but there are 2 of them)
The tacho circuit ground wire is connected to the same motronic pin for the cyl 1/4 coils.
If either of the ground lines going to the motronic are skinned/hard grounded then the tach won't work and the cyls won't fire.
You could possibly have a failed coil.

It's hard to say from here, all we can do is offer suggestions for what to check.

Thanks - that gives me a good place to start looking,although it might be tricky identifying which one of the motronic pins or wires is the one you mention,but at least its somewhere to start
Thanks
Dave

[Laitch]

Thanks - that gives me a good place to start looking,although it might be tricky identifying which one of the motronic pins or wires is the one you mention,but at least its somewhere to start

Pin 19 is often referenced for this function.

[Scott_]

Laitch, looking at my slp bmw diagrams, I'm slightly confused. I've looked at multiple 1100's us and eur version and....
It indicates that pin 20 is for cyl 1/4 coil and pin 19 being shared for cyl 2/3 and the tach. Which isn't matching the op's symptoms.

[Laitch]

I'm slightly confused. I've looked at multiple 1100's us and eur version and....

Between us I doubt if you're the one who is actually confused, Scott_. :giggles
Now Blue's got a pin connection he can check based on your experience and reference.

[BlueK11LT]

Can anyone tell me where I can find a diagram of the motoronic pin layout so that I can identify which one is no.19?
Ive tried doing google searches but iam not having much luck
Dave

[Inge K.]

http://www.motobrick.com/index.php/topic,3149.msg18935.html#msg18935

MA 2.1 and MA 2.2 is similar, just the connector orientation is different, on MA 2.2 upper becomes right side.

[BlueK11LT]

http://www.motobrick.com/index.php/topic,3149.msg18935.html#msg18935

MA 2.1 and MA 2.2 is similar, just the connector orientation is different, on MA 2.2 upper becomes right side.

I had seen that photo before but did not think it related to the 1100 as the thread was about a K100.
Having looked at my motronic plug there does not seem to be anything obviously wrong with any of the pins,and although the outer sleeve of the wiring to the plug is disintegrated a bit there does not look to be any bare wires within.
I will give it a better looking over at the weekend to see if I can find anything wrong.
Dave

[BlueK11LT]

After checking the bike over it seems that I might have a dead coil for no1&4 cylinders.
After testing both low voltage plugs to the coils ive found that both are getting power to the coils.
If I attach no1&4 plug onto no2&3 coil I get a good spark when cranking the engine,so this makes me think that no1&4 hall sensor is ok,but when I attach no2&3 plug to no1&4 coil I get no spark.
Ive bought a pair of coils from an ebay seller which have been taken from a running bike so hopefully it should cure the problem.

[Martin]

 :2thumbup:
Regards Martin.

[BlueK11LT]

Fitted replacement coil today - success,bike running great again on all 4 cylinders,and tacho working again.
Must say it is one of the fiddliest jobs ive ever done on a bike due to the inaccessibility of the mounting bolts.
Dave

[Brad-Man]

 :clap:

Excellent news and thanks for posting the fix!

[Laitch]

 :2thumbup:

[84K100RT]

As a thought on this best to swap the coils when this happens so as to rule out the possibility of it being a coil, no new parts needed. If it's a coil problem then the issue will swap from 1/4 to 2/3. If the problem doesn't swap with the coils then both coils are good so now suspect the Hall Sensor.