Hi, fellas:

I'm new here and almost new with a K75. Have been 8 months now of restoring and customizing and now I'm stuck with a problem.
I bought an Acewell MA085 (analogic RPM & digital speed) with a BEP 3.0 and all seems to be working fine: rpms, light, bargraph fuel...

BUT speed. 

I have followed the cafe4racer schematic, so green wire into SPD connector. Then I put my wheel measurement (arround 1950) and the pulses (which are 6 or P-006). The K bike is in a stand so I started it and accelerated with the gear 1 to move the back wheel but the speedometer is not working at all. Sometimes, if I move the wheel with my hands I get strange readings (0 km/h -> 299km/h -> 34km/h...) but not always work that way. Most of the time it only shows '0km/h'. 

I have seen that there is a switch to move from 0/5V to 0/12V, but there is no real change. (I don't really know what is this for)

One thing I can't understand is that all my Acewell MA085 black (ground) wires are attached to a washer so I screwed it to the chassis, but there is a black wire going into the GND BEP 3.0 in the schematic. I tried to put a wire in there and attached it to the chassis also with no changes so: is it necessary to put one of the black wires of the connector in the BEP 3.0? I though it wasn't a problem because everything is working fine but that.

Searching in google I found this in this forum: "When I hooked the speed+ from the Acewell to the SPD input on the BEP I got erratic readings at first. It would say "0mph" then would jump around when I revved it in neutral. I was concerned it wasn't going to work, but once I rode the bike around the block it stopped doing that almost immediately. Perhaps it needed to see a signal from the sensor to calibrate itself."

Do you think there is a chance the speedometer works by itself one I take a ride arround?

First check to see if you have ground on the connector that interfaces to your speed sensor - the two-pin one behind the right side cover
Disconnect the sensor and check into your main harness side, that the brown wire terminal is indeed short to frame ground.

Next, a useful tool I found when troubleshooting the system was to make up the test cable and use the Karamba test program
https://www.k100-forum.com/t2038-karamba-speedometer-calibration-program-tutorial
The link in that thread is broken but you can get it from post #20 in this thread - https://www.k100-forum.com/t9583-karamba-speedo-software
It takes away any question of issue with the speed sensor itself - indeeed in the case I was working, the speed sender was bad!
The test lead is easy enough to make up if you have an old audio jack but of course you need a laptop that you can place next to the bike.

On the instrument side of the BEP3, you should have a ground wire (black) from the Acewell, connecting into the GND terminal on the output side of BEP3 (however it should be the same thing if you have connected the black wire directly to ground - frame)

(edited) The switch (so that's what it's for!!! Thank you!) I would believe should be set for 5V (Acewell uses a 5V 2-wire Hall Sensor so that is the signal level it is expecting)

D'Ecosse wrote:First check to see if you have ground on the connector that interfaces to your speed sensor - the two-pin one behind the right side cover
Disconnect the sensor and check into your main harness side, that the brown wire terminal is indeed short to frame ground.

Sorry, but I don't understand you at all 
- When you say 'the connector that interfaces your speed sensor' yo mean the BMW connector coming from the rear wheel sensor? In that case It has been working (with the 'lunchbox') until I put the Acewell so It should be OK.
- When you say 'that the brown wire terminal is indeed short to frame ground', did you mean a brown connector that comes out of the Acewell or are you referring to the original wiring of the BMW? The brown connector of my Acewell goes to the BAT connector of the BEP (See attached document).

Next, a useful tool I found when troubleshooting the system was to make up the test cable and use the Karamba test program
https://www.k100-forum.com/t2038-karamba-speedometer-calibration-program-tutorial
The link in that thread is broken but you can get it from post #20 in this thread - https://www.k100-forum.com/t9583-karamba-speedo-software
It takes away any question of issue with the speed sensor itself - indeeed in the case I was working, the speed sender was bad!
The test lead is easy enough to make up if you have an old audio jack but of course you need a laptop that you can place next to the bike.

Thank you very much for this tool, I will try to make the wire to make it work.

On the instrument side of the BEP3, you should have a ground wire (black) from the Acewell, connecting into the GND terminal on the output side of BEP3 (however it should be the same thing if you have connected the black wire directly to ground - frame)

About that sentence: It is the same if I put a wire into the GND connector and attach it to the ground - frame? Or It MUST be connected to the Acewell black wire EVEN if all the other things are working fine?

(edited) The switch (so that's what it's for!!! Thank you!) I would believe should be set for 5V (Acewell uses a 5V 2-wire Hall Sensor so that is the signal level it is expecting)

Thanks about that! I have tried to put the Hall sensor and change the Acewell option for that and if I move the magnet arround it works. 

I answer you between lines, thank you very much for your help!

Attached file:  http://forum.kforum-tech.com/members-upload/uploads/ACE_MA85-X54W_Vers_A_Anschlussplan_eng.pdf

1. The 2-way connector (behind right side-panel) that connects the OEM speed Sensor to the Main Harness
Disconnect the sensor
Set meter to resistance
Connect one probe to the terminal that has the brown wire in the connector on the main harness side (not the sensor side)
Connect other probe to frame
Check that you get continuity (zero ohms)
Although you believe it all worked before, just verify that you do still have this connection to ground.
Incidentally when you connect the Karamba, you will connect into this same connector with your test lead (but of course will connect to BOTH terminals of the connector, the signal to the yellow wire and the ground from the cable to the brown wire)

2. No (to answer your question exactly "is it the same" )
That GND terminal on the BEP3 is already connected internally to Ground inside the box
So if you connect a wire from the GND terminal to an actual frame ground point, you are simply connecting it AGAIN to ground.
What is important is that you have the Black Ground wire from the Acewell to 'a' ground point - whether you use the BEP3 GND terminal or actual frame ground, should not make any difference - but Acewell black ground MUST be connected to one or the other.
Notice that in your attachment you can see that the Black wire from the Acewell connector goes directly to the GND terminal on the BEP3