Rewiring 1985 k100

[Roland]

Hello, I am trying to rewire the ignition system on my bike to be isolated. I am doing a custom build and am no longer using the stock wiring harness or fuel injection. All sensors but the rpm sensor has been removed. I really need to know where power need to be routed to the ignition module and where it goes afterward. I forgot to pin out the wiring harness before I got rid of it so that is why am am asking here and not just doing it myself. My bike is a 1985 k100rt. Thank you for your time.

[rbm]

Woah, you certainly are sailing in uncharted waters, Roland.  Here's a link to the schematics for that model year bike:

https://drive.google.com/open?id=0B3UPbNZRyr1ramNaQ19DM3Z6TTQ

The ignition components are in the upper right corner (ICU, ECU, coils, etc.).  Power leads are usually Green/Black and grounds are usually Brown.  Good luck.

[Roland]

Thankyou for the response. Is there any way someone could label the inputs and outputs on the ignition module. I have a wiring diagram from the manual but I cant seem to figure out why there are wires running to fuel injection, fuel injection relay and other assorted components that seem to have nothing to do with ignition. Thanks  :2thumbup:

[rbm]

I'm really intrigued as to how you're going to accomplish this ... putting carbs on a K100 then hacking in the ignition.  Normally carbureted engines get their spark timing from a distributor geared to the crank of the engine.  Timing is adjusted by vacuum operated advance mechanisms, which are all missing on the K-bike.  All you have is a hall sensor to indicate TDC on a FI injected bike.  Since you'll be taking away critical sensors like the MAS, TPI, temp sensors, and others,  how are you going to fool the ICU to generate a correctly timed spark when it has no information about the state of the engine?

You can read up on L-jetronic and how it works here:  http://www.cardiagnostics.be/-now/Educational_sites_bestanden/BOSCH%20L-Jetronic%20Injection%20Manual.pdf

[Roland]

so as i am looking at the wiring diagram, I only see one signal wire coming from the ECU and connecting to the ignition box. I would assume that this has to be an output from the ignition to the fuel injection and not the other way around. this being the only wire means that it must carry crankshaft position signal to the ECU. Please confirm if this sounds right. In addition, while looking at the diagram I think that the green/yellow wire going to the ignition box is the power for both the coils and the box. Would it be possible, for someone to pin out their connector to the ignition box to determine if what I am saying is correct? What i do not know is the functions of the yellow/brown, purple/grey, Brown/red, and the Black/yellow wires coming out of the ignition box. Why would it be connected to the starter relay? Why is it connected to the fuel injection relay on the grounds side? why is it connected to an unknown vacuum switch? Why is it connected to the starter switch? If someone could pin these out with a volt meter and find power and ground cables that would be much appreciated and may help people better understand this system and help them in the future. Thank you and have a nice day  :2thumbup:

[rbm]

so as i am looking at the wiring diagram, I only see one signal wire coming from the ECU and connecting to the ignition box. I would assume that this has to be an output from the ignition to the fuel injection and not the other way around. this being the only wire means that it must carry crankshaft position signal to the ECU. Please confirm if this sounds right.

Correct, Yellow/Red on pin 8 of the ICU is an RPM signal output going to pin 1 of the ECU

In addition, while looking at the diagram I think that the green/yellow wire going to the ignition box is the power for both the coils and the box. Would it be possible, for someone to pin out their connector to the ignition box to determine if what I am saying is correct?

Yes, Green/Yellow is switched 12V power to the ICU pin 10 and high side of the coils.

What i do not know is the functions of the yellow/brown, purple/grey, Brown/red, and the Black/yellow wires coming out of the ignition box. Why would it be connected to the starter relay? Why is it connected to the fuel injection relay on the grounds side? why is it connected to an unknown vacuum switch? Why is it connected to the starter switch? If someone could pin these out with a volt meter and find power and ground cables that would be much appreciated and may help people better understand this system and help them in the future. Thank you and have a nice day  :2thumbup:

Yellow/Brown on pin 7 is grounded when the ICU wants to turn on the FI relay, during cranking and engine running.
Black/Yellow on pin 6 is 12V power from the start button. it tells the ICU that the operator wants to crank the engine.
Brown/Red is ground for the starter relay.  This is connected to ground when the engine starts cranking but gets cut when the RPMs exceed 720 RPM.
Brown on pin 1 is ground
Black/Red on pin 9 and Black/Blue on pin 14 are coil primary low side.  The get connected to ground to fire the coils
Purple/Green on pin 15 comes from the vacuum switch and can mostly be ignored.
Pins 13, 5, 3, 2, and 4 come from the Hall Sensor array and signal crank position to the ICU.

[Roland]

That is extremely helpful and will let me wire this. You gave me everything i needed to know. I cannot thank you enough!  :2thumbup: :2thumbup:

[rbm]

Best of luck with your endeavour.  I'm hoping this works out because the information would be valuable for the rest of us.

[Roland]

It worked out very well. with no other systems other than the ignition box and the pickup it ran very well.





link to video of it running

[RavenRed]

Any more details on this? Carb model and such? I have been contemplating doing this to my brick since I received it in a box and the harness is kind of a mess. Thanks!


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[Roland]

Bmw k100rt is the model bike. A weber sidedraft 40dcoe is the carbeurator. If you dont know how to do a custom manifold as pictured. It might make more sense to use 4 motorcycle carbs off of another similar year bike or potentiolly newer. Been running into some problems with theottle placement and leakage from the throttle body booties.

[RavenRed]

Bmw k100rt is the model bike. A weber sidedraft 40dcoe is the carbeurator. If you dont know how to do a custom manifold as pictured. It might make more sense to use 4 motorcycle carbs off of another similar year bike or potentiolly newer. Been running into some problems with theottle placement and leakage from the throttle body booties.

I have the same bike but it came in various boxes. I have no problem fabing an intake to work but I also know they can be fickle at times so that’s why I was asking about carb model so I could get an idea of the CFM. I like the idea of running a carb but haven’t messed with them in ages. I’m still feeling out what would be the best configuration. Hell, if I’m running carbs I may go ahead and throw a small turbo on it just for grins. Really the goal for me is to clean up the engine bay and do away with everything not needed in the harness and such. I’m trying to minimize everything and go as bare bones as I can.

[Roland]

That was exactly my coal with mine. I reccomend just starting from scratch with the harness except for certain special connectors like alternator