Recently fitted to my K75 an Acewell 4454 instrument connected it to a Maru-Labs bep3.0. 
Experiencing some problems:-

Tach needle fluctuates. Not steady. Also seems to overead. It’s connected to the bep 3  RPM output. I have also tried fitting the supplied 100 ohm resistor. Then rpm ceases to function. 
Now want to connect tach directly to no. 1 ignition coil as suggested in Acewell 4454 user manual. Not sure which wire to connect directly to on ignition coil. 
Can I wire to any of the other ignition coils?

I have also wired 4 separate led warning indicator lights connected to the outputs of the bep 3:-

WRN.  my led does not switch on when ignition is switched on. 
BAR.  This led switches on when fuel level is 4Litres and lower. ( working)
ALT. Not sure how to use this function. I had a led light connected to to this output. When bike is running light remains on. 
CHK. My led light does not switch on when choke is activated. 
TMP. I have a led light connected to this output. Hope it will switch on if there is an over temp situation. 

I still need to fit the supplied water temp sensor. The thread of the sensor is 1/8”npt and will not fit the thread of the drain plug in the water pump housing  which is M10x1. Will need to source a suitable adapter. I’m also considering an adapter which will fit into small hose that is behind radiator. What is inside diameter of that hose?

Here is when you use the Forum's search engine, conveniently located both on the Portal page and the Forum page. Try typing in BEP, Maru and/or Acewell where you'll find a whole load of info concerning other member's troubles & potential fixes pop up. And good luck with your search. Other user's may offer their personal Acewell & Maru BEP advice, coming along soon.

Careful using the output from the primary of the coil directly.  It can produce spikes of 80V or more.



You might want to use a resistive voltage divider to reduce the size of the spike.

As for needle instability, do you have the wires bundled together?  You might be experiencing crosstalk between wires that is messing up you tach input.  Try unbundling any wire bundles and spread out the wires.

As for your indicators, you have to figure out what you want first.

WRN - this is a collective warning light if any one or more of the following warnings occurs, the lamp will turn on -  Brake test, ABS warning, alternator failure, coolant overheat, oil pressure low, choke on.  If, for example, you just turn on the ignition without starting the engine, the WRN output will light up because of alternator failure, brake test and oil pressure.

TMP - this warning happens when water temperature sensor in the radiator stump on the block senses too high temperature.  you can simulate overheating by shorting pin E on the temperature module in the relay box to ground while the ignition is on.

ALT - this lights when the alternator is not charging.  When you turn on the ignition but don't start the engine, the alternator is not charging. The light goes out normally when the engine is running and the RPM exceeds 1500RPM. If the engine is running and this light comes on, the alternator has failed.

CHK - if you have a choke switch attached to the throttle bodies, then that switch will light up this warning.  It means choke is on.