Hi
My K100rt 84 has hard cold start any advice?
Thank you

Because you have customized your moto, additional information is needed. Did you retain the increased start speed (choke) lever and its connection, the air flow meter, the throttle position sensor and the z-tube crankcase hose connection to the intake air stream? Have you done a valve clearance check and a throttle body balance? Have all the hoses and the fuel filter within the tank been verified in good condition, or replaced?

Yes I kept everything and fully serviced the valve clearance and throttle balancing left to check!Once she starts runs well?!

Does the choke (fast idle) increase the revs once started? Try moving the lever past the first detent does this help?
Regards Martin.

Hi
Only when she starts warm up then gradually increases the Revs?!Any ideas?once she starts runs well!
Thank you!

The electrical connector's contacts to the air flow meter could be dirty or the plug itself not connected tightly enough. Check it and clean it with electrical contact cleaner. The vane in the air flow meter (red arrow) might not be swinging smoothly enough and/or the air temperature thermistor (green arrow) might be dirty so its signal isn't correct. Gently push the vane with a dowel to its full range. It should move smoothly. Electrical contact cleaner could be carefully applied to both parts for cleaning and lubrication.

The air filter should be relatively clean and in good condition. The z-hose should be tightly connected and without cracks.

I solved cold start issue this morning with simple and easy action. Culprit was tank plug on the left underside. Try to squeeze four female contacts and clean with some deoxit or wd 40. Your bike was 84 with that early problematic four pin connector.

After a short failed start, I would pull the plugs and check their condition. Wet or dry? That will give you some idea of where to start looking.

Hi everyone
So an update for my cold start I have checked the maf sensor it’s definitely working well because I started her and once she starts runs well and I watched it and it’s opening nicely when I was rev her!The tank connector it’s just working because the bike is running with an m-unit motogadget so the pump is running on ignition. I have replaced the coolant sensor and the first attempt to fire her up surprisingly she just started instantly I was so happy BUT next morning same issue
I think she runs too lean because if I disconnect the sensor she fired up instantly but smoking?!
It’s annoying because when I managed to fire her up she runs nicely?!

As per Holister are the plugs wet or dry.

I only ask because it’s the sort of thing I’d do: if you can see the MAF operating, does that mean you have opened up/deleted the airbox?

I just opened it up to check it

It’s the original setup with new filter cleaned etc!

Hi all,
my friends bike has cold start issues since he bought the bike. It starts a bit hard and runs roughly until the engine gets warmer. Warms start is fine. I think it might be a problem with the cold start enrichment. I think there must be a secound temperatur sensor on the block of the engine that gives signal to the ECU regading motor temoeratur condition. So far we could not find it. Before we tear down the bike I want to know if one can tell me where to find this secound sensor. 

Bike is completely stock, no changes, warm running is fine, 73.000 km.
Airfilter is new, spark plugs new, oil new, valve timing was checked and adjusted in workshop.

Thanks
Rgds Martin

Check the switch on the throttlebodies, wich is for the "choke".

martin_the_last wrote:I think there must be a secound temperatur sensor on the block of the engine that gives signal to the ECU regading motor temoeratur condition. So far we could not find it. Before we tear down the bike I want to know if one can tell me where to find this secound sensor. 

What is the first temperature sensor, Martin, the air temperature sensor in the air flow meter? 

If, as Arlina suggested, checking the "choke" switch doesn't reveal a problem, the coolant temperature sensor mounted in a pipe that connects to the radiator could be faulty and signaling to the Jetronic control unit that the engine is warm when, in fact, the engine is cold. If that is happening, the starting fuel mixture will not be enriched enough and starting will be difficult. Once the engine is started and warmed up, the engine will start OK, until it cools down thoroughly, then starting will be difficult again. The coolant temperature sensor is within the blue rectangle in the Max BMW diagram I've posted here. The coolant temperature sensor also has a separate function that sends a signal to activate the coolant temperature warning light in the instrument cluster when the engine is overheating.

Find testing procedures in this document within the Tech Page. Scroll down to the LE-Jetronic (EFI) Test to learn how to test it electronically. You could also remove it to perform the boil test and determine its function according to resistance values on the test table.

Assuming your friend's bike is an 8 valve model with a Jetronic engine control unit, disconnect the big connector under the seat and check the resistance between pins #10 and #13.  When the engine is cold you should see around 2500 ohms.  As the engine comes up to operating temperature the resistance should drop to about 250 ohms.

That 2500 ohms tells the Jetronic to make a richer mixture for starting.

It is also possible that the crankcase breather known as the Z tube may be cracked and creating an air leak that makes the mixture too lean.  Look for the cracks near the hose clamps that hold it in place.  That tube is a known source of trouble.

Arlina wrote:Check the switch on the throttlebodies, wich is for the "choke".

Hi Arlina, thanks. I will do. Please see attached picture. I hope it will be uploaded. Which switch do you mean? the 13? How can I test it easily? The nr. 10 is a pressure switch.

Rgds Martin

Hi Laitch,
normaly L"x"-tronic systems from bosch work with 2 seperate exchangable temperature sensors. I dont mean the one in the air flow meter. 1 in the radiator as described from you and 1 directly mounted on the block for / also for the cold start enrichment. This enrichment systems normal work for 5 to 10 secounds after a cold start or longer? And this sensor for the enrichment is the one I have meant.
The sensor in the radiator cannot be the one for the enrichment because the thermostat will open open the big coolant cycle only very "late" if temperature is high enough. 
Anyway - I take a look at the trouble chooting page you send in the post.
Thanks. Martin

Point-Seven-five wrote:Assuming your friend's bike is an 8 valve model with a Jetronic engine control unit, disconnect the big connector under the seat and check the resistance between pins #10 and #13.  When the engine is cold you should see around 2500 ohms.  As the engine comes up to operating temperature the resistance should drop to about 250 ohms.

That 2500 ohms tells the Jetronic to make a richer mixture for starting.

It is also possible that the crankcase breather known as the Z tube may be cracked and creating an air leak that makes the mixture too lean.  Look for the cracks near the hose clamps that hold it in place.  That tube is a known source of trouble.

Hi point-seven-five, Thanks. Correct - it is an 8V version. I will check the Ohms as you said. Thanks a lot. And I will also checkt the z tube. Good idea. I havnt thought about that so far but is in fact a source failure very often. Thanks. I will check. 

Rgds Martin

martin_the_last wrote:This enrichment systems normal work for 5 to 10 secounds after a cold start or longer? And this sensor for the enrichment is the one I have meant.

That's the coolant temperature sensor to which I referred, Martin.

The coolant temperature sensor isn't in the radiator; it's in a pipe screwed into the block connecting the coolant in the radiator to engine block cooling passages by means of a hose from the radiator. It's measuring the temperature of the coolant before, and after, the thermostat opens. Its responding to the temperature of water in the block. As the water warms, its signal to the Jetronic changes and the fuel mixture becomes more lean. All this is happening before the thermostat opens.

Here's a chart from a compelling literary work titled Level 2: LE Jetronic. It describes our 2V( also known as 8V) Brick engine management system. The author seems to be BMW but there is suspicion it was ghost-written by Bosch, the manufacturer. Some readers might find it boring, others might find it mysterious. Anyway, the chart shows the engagement of the various electronic engine management's components at each stage from ignition through warmup. Each X in the chart indicates the engagement of a particular component during a stage of warmup. The pressing of the starter button starts enrichment but the coolant temperature sensor is the major player until the engine is warmed up. Note the time intervals in the chart.



My first response to your query suggested only that this sensor is a possible source of your current trouble and that there is more left to learn concerning it. When you measure at pin #10—as Point-Seven-Five suggested, you are measuring the coolant temperature sensor's input contributing to fuel mixture control.

martin_the_last wrote:

Arlina wrote:Check the switch on the throttlebodies, wich is for the "choke".

Hi Arlina, thanks. I will do. Please see attached picture. I hope it will be uploaded. Which switch do you mean? the 13? How can I test it easily? The nr. 10 is a pressure switch.

Rgds Martin

Switch 13 indeed

Point-Seven-five wrote:Assuming your friend's bike is an 8 valve model with a Jetronic engine control unit, disconnect the big connector under the seat and check the resistance between pins #10 and #13.  When the engine is cold you should see around 2500 ohms.  As the engine comes up to operating temperature the resistance should drop to about 250 ohms.

That 2500 ohms tells the Jetronic to make a richer mixture for starting.

It is also possible that the crankcase breather known as the Z tube may be cracked and creating an air leak that makes the mixture too lean.  Look for the cracks near the hose clamps that hold it in place.  That tube is a known source of trouble.

Hi point seven five, with 8° C the Ohms between 10-13 is around 1950 Ohms. Sounds okay in my opinion. The Z tube was changed already from him. But we will take a look again to all air leading tubes and stuff behind the air flow meter.

At 8C the resistance should be quite a bit more than 2500 ohms.  I'm not sure this is your problem, but it's something to keep in the back of your mind as you work on the other tests.

The temperature sensor should go in clean and bare, any thread tape, sealant or corrosion can interfere with it's function. It relies on the seal/gasket to prevent leaking.
Regards Martin the Ozinian.

Point-Seven-five wrote:At 8C the resistance should be quite a bit more than 2500 ohms.  I'm not sure this is your problem, but it's something to keep in the back of your mind as you work on the other tests.

Okay, do you know which sensor it is that leads to the pins 10 and 13? Do you konw which one it is and where to find it on the motor? Maybe we will just change it if it is not too expensive.

MartinW wrote:The temperature sensor should go in clean and bare, any thread tape, sealant or corrosion can interfere with it's function. It relies on the seal/gasket to prevent leaking.
Regards Martin the Ozinian.

Hi, thanks also for your answer. But can you also tell my which sensor exactly yo mean? So far we have found a few sensors and so far from half of we know what they are. But from still not So can you explain which sensor you mean and where it is mounted. Thanks.

Laitch wrote:

martin_the_last wrote:This enrichment systems normal work for 5 to 10 secounds after a cold start or longer? And this sensor for the enrichment is the one I have meant.

That's the coolant temperature sensor to which I referred, Martin.

The coolant temperature sensor isn't in the radiator; it's in a pipe screwed into the block connecting the coolant in the radiator to engine block cooling passages by means of a hose from the radiator. It's measuring the temperature of the coolant before, and after, the thermostat opens. Its responding to the temperature of water in the block. As the water warms, its signal to the Jetronic changes and the fuel mixture becomes more lean. All this is happening before the thermostat opens.

Here's a chart from a compelling literary work titled Level 2: LE Jetronic. It describes our 2V( also known as 8V) Brick engine management system. The author seems to be BMW but there is suspicion it was ghost-written by Bosch, the manufacturer. Some readers might find it boring, others might find it mysterious. Anyway, the chart shows the engagement of the various electronic engine management's components at each stage from ignition through warmup. Each X in the chart indicates the engagement of a particular component during a stage of warmup. The pressing of the starter button starts enrichment but the coolant temperature sensor is the major player until the engine is warmed up. Note the time intervals in the chart.



My first response to your query suggested only that this sensor is a possible source of your current trouble and that there is more left to learn concerning it. When you measure at pin #10—as Point-Seven-Five suggested, you are measuring the coolant temperature sensor's input contributing to fuel mixture control.

Hi again, 

okay, then I will check that again a bit more in depth.  thanks for the tabel. looks promissing. after I have checked all this I can hopefully say "way got it". Thanks so far.

Post # 16 in the blue outlined box, it goes into the stack pipe below the radiator hose. The pipe is located behind the radiator on the LH side. Due to it's location it can be subject to road spray and assorted road crap. This can lead to a bad/intermittent connection on the wiring plug due to corrosion.
Regards Martin the Ozinian.
.

Number 16;
(I know it's a K75, but same as K100 2V)
(Your sensor doesn't have a wire, like every 2V sensor)

https://www.realoem.com/bmw/en/showparts?id=0563-EUR-10-1987-K569-BMW-K_75_S_0563,0572_&diagId=17_0628