Greetings to all vintage motorcycle enthusiasts.

I want to offer you my experience in the repair of a breakdown, 
that with the invaluable help of the document ''bike won't start" I was able to solve.

Summary:
Problem
 I buy k75 running I put documents up to date, but it had 
 been 5 years without maintenance.

 I start buying filters, sensors etc... and so on... 
 and after several weeks of cleaning and disassembly, 
 when trying to start the bike... no way... overboosted, it chokes constantly.

Failed attempts of repair:
 Revision of fuel-pump and change fuel filter.
 Change of rubber ducts, of all the feeding circuit.
 Change of the fuel pressure regulator.
 Disassembly and revision of the air flow sensor./That was funny...
 Revision of the operation of injectors.
 Change of the 3 spark plugs.

 After many hours of searching in forums... 
 I decide to take it to a profesional BMW mechanic in Valencia-Spain (BoxerVal). 
 
 That guy 3 weeks after, tells me that I have to change the injectors 
 for original ones, (600€ only in parts...)

 It was clear to me that the bike injects as it should / intermittently...
 In fact when I was doing my tests, I almost set the bike on fire
 taking out the injectors to see if they worked.
 Besides talking some owners, they pointed never changed that...   

 At that moment, once paid 200€ for nothing !!! to that mechanic....
 I decide to bring home again the bike...

Final solution:
 I was considering to change the control unit .... but the bike run when I bought it.
 And suddenly I get my hands on the forum document:

https://www.kforum-tech.com/forum-area/__Files/electrical/EFI/bike-wont-start-EN.htm

 I found after many hours with the tester ... the problem:

 Result: The water temperature sensor that I bought new, had a fault.

 I detect it with the T vs Ohm >> Graphic of Cooling water temp Sensor:
   For 25ºC corresponds >> 2.5K Ohm 
   My New sensor reading: 8K Ohms >> corresponds to -10ºC...
   -10ºC >>> needs a lot of gas supply...

  The bike thinks it is at -10ºC when lucky for me, in Valencia 
  we were at 30ºC, it injects so much fuel that it chokes permanently.

  Once replaced the old 20 years old sensor ... runs on 1 try... Yeahhh


Thanks Laitch >>>

After 1000 hours...
Here details of the doc and the key of the issue...






Regards.

Congratulations on deciphering the no-start issue, a good job, with informative details. I have moved your thread from general troubleshooting to the more specific engine troubleshooting.

You'll be able to post pictures after, I think, five posts. It's more complex than it should be, but not difficult once the procedure is learnt and followed.

The easiest way to understand it is to type "posting pictures" into the search engine on the main forum page. Several results will appear. Take your pick. You can use an external "host" or simply download your own from your files.

congrats, Quille.
Well done

Where did you buy the water temperature sensor?

Its possible you got one for a 16v engine, they look the same but are different.

92KK 84WW Olaf wrote:Where did you buy the water temperature sensor?

Its possible you got one for a 16v engine, they look the same but are different.

I can't find one listed for the 8v anywhere.

Skidmark wrote:

92KK 84WW Olaf wrote:Where did you buy the water temperature sensor?

Its possible you got one for a 16v engine, they look the same but are different.

I can't find one listed for the 8v anywhere.

The water temperature sensor for 2V engine (K75/K100) fuel injection readings is shown in ETK under cooling with the radiator. Item 15. 

61 31 1 459 197.

Bosch part number for K75/K100 temp sensor is 0280130069.

The new sensor, I bought it at AUTODOC.
https://www.autodoc.es/stark/15796761

The product information sais that it was compatible, 
but that was the key to my problem.

With other parts, filters, fans for other repairs....
sometimes I found few problems...
But after this experience I will double check every item.

Once the old one was installed, the problem disappeared.

I haven't been in here for a few days. 

I got some from www.tills.de and have one or two in my shed. I have had the same issue which is what prompted me to ask about the sensor when I saw you had replaced it.