Hi ALL, thank you in advance for your replies.

Would like to know if is possible to fit on a BMW K100RS with co2 sensor and exhaust Catalyst
the ECU of a same model bike but without the co2 sensor and cat? 
I know for a fact that BMW K100RS 16v came with and without Cat and co2 sensor.
I am modifying my bike and want to fit another exhaust. I read that if the bike is fitted with cat originally 
and we remove the original exhaust it will become very rich. so i think if we fit the ECU from the bike
without cat it should work. Am i right?
Anyway i have a NO START, NO SPARK and after checking everything, i am ordering the Hall sensor and 
i am looking for a used ECU but can not find any for my Cat bike but there is one for same bike without cat.
Sincerely appreciate any opinion. Cheers. Safe rides

I have bikes with both versions of ECU

They both have different ignition looms, the  ECU with Cat loom has the plug for the O2 sensor.
The other one has a  connector for a rheostat fitted at the front of the fuse box, this rheostat will be missing from your bike.

Therefore to convert you will need an ECU (non CAT), Rheostat and correct ignition loom.

I did try the KAT ECU on the non KAT bike and it did start but I never took it on the road.

Thank you. My bike as Kat. But I want to remove it. So my question is the opposite you did. Want to fit a Non Kat ecu on my Kat bike.
Please forgive.. I am Zero on this electric stuff. Could you please be more specific what I have to do if I fit a No Kat ecu on my bike? No idea what is that Rheostat and when you say Correct ignition loom means I have to be playing with those all bunch of cables? OMG

I will take a few pictures later to try and explain better for you.

You will need 3 items

1. Motronic (Non CAT)
2. Ignition Loom with connecter for Rheostat aka Potentiometer - this will replace your loom that has the O2 sensor plug
3. Rheostat (this is fixed to front of relay box on the non CAT bikes)

Sincerely appreciate. When you said Loom is the cables that go to the co2 sensor? I did not see where those cables go. I will check

This is how the mixture is adjusted on the non-CAT bike

It will not be fitted to your bike but hopefully the pictures give you an idea what you require

The connector in my hand connects to the rheostat in the previous post.

You will need a loom like this to do your conversion, your loom will have the round connector that connects to the O2 sensor in the exhaust

Thank you so much for your time.
Oh man... So i need to change all loom from my bike and get a No Kat loom is it so?
No way to cut the cables that goes to co2 sensor and convert it to the rheostat?
What can happen if I just plug the other ecu? And connect the co2 cables together... I think is 2 cables od it go all on fire?,

I see you have the loom in your hand so maybe you don't need it and I can buy it?

Mate. Only now I see. You are from Ireland. Blessed beautiful country. I lived in Ireland 7 years before I came to Finland
Near Cork. Cheers. I wish you and your family to be safe and healthy in this difficult pandemic times. God bless

Unfortunately my cable is not available.

I see you have some other posts up.

It might be better to get the bike running before you make any modifications.

Yes dear. That is the idea. But because I am a Zero on electrics and don't know how to test stuff
.. Have to buy things and see. Today I get the hall sensor. I fit it. Tomorrow and see. If not work, going to order the temperature sensor. If does not work... I try to find the ECU. But the thing is I can not find the original ECU so I am goi g to buy the one I told you for no Kat bike and see if works.
Man what makes. Me crazy is if I disconnect the battery and leave it like an hour and plug it again, when I crank the bike it seams want to start... Then nothing