Hi all,

I'm working on a 1989 K100, which is done and running fine, except the fuel consumption.

Actually I'm about 10L for 100km, is quite high.

I've checked a lot of things, but I don't know what to search now...

- All is brand new on the tank, except the fuel pump
- there is correctly fuel returning on the tank where running
- Pressure is above 2-2.5 bar on the injection ramp
- injector are working, but I didn't test them on a specialist, but filters, seals are new, and they did pass in the ultrasonic tank for some time
- depression tube on the 4th cylinder is new
- the little hose between the block and the air filter is new 
- I've visually synchronized the 4 air intakes
- TPS is in good position
- air filter is new

But it seems the bike is always too rich... any idea?

Sorry for the english.


Thanks

Sounds like the temperature sensor is out of range. Check the portal page and go to the tech forum page here you will find info on checking it.

Rick G wrote:Sounds like the temperature sensor is out of range. Check the portal page and go to the tech forum page here you will find info on checking it.

Hey

Actually I forgot to write it on the first post, but I did check the temperature sensor.
Got 2200 ohms at 25°C, and above 180 when the fan start.
Seems not bad ?

How many kilometers on the odometer? Is that figure accurate?

Laitch wrote:How many kilometers on the odometer? Is that figure accurate?

This K100 got 196000 kms. The daily odometer is working good, it's some work/home trip so I got a good reference :p

How much oil does it consume?

Actually it doesnt consume it (or not enough to see it)

Are acceleration and idling acceptable?

Laitch wrote:Are acceleration and idling acceptable?

Idling is good when motor is hot, acceleration is good, but i didn't push it to the limit (to 6000rpm it's good)

Describe the idle when the engine is cold. Do you use the starting speed control (choke)?

Yes, if I start the bike cold, i have to use the choke at half at least some minutes

What is the make and part number of the spark plugs?

Oh good question... Need to check if there is something on it...

I think these are originals bmw

That is the worst fuel economy that I have ever heard of on a K100.  I am surprised it actually starts and runs without being flooded.

Does the exhaust smell of fuel(or elderberries*) when the engine runs?  Does fuel leak from the exhaust joints?  There has to be a lot of unburned fuel going through the engine.

Are you sure that your odometer is reading accurately?  I would suggest checking it over a known distance of at least 20km.

*Unfortunate Monty Python reference.

Point-Seven-five wrote:That is the worst fuel economy that I have ever heard of on a K100.  I am surprised it actually starts and runs without being flooded.

Does the exhaust smell of fuel(or elderberries*) when the engine runs?  Does fuel leak from the exhaust joints?  There has to be a lot of unburned fuel going through the engine.

Are you sure that your odometer is reading accurately?  I would suggest checking it over a known distance of at least 20km.

*Unfortunate Monty Python reference.

Yes it start correctly, and seems not flooded.

The exhaust smell a little the fuel, but not that much for a bike of this age.. 
There is absolutely no leak.

The odo is managed by a tenet, but speed seems verry accurate, i will recheck but i think i can say it's good too.

I really don't understand what it can be...

Maybe the engine is running fine but it's having to work against another problem? A dragging brake? Slipping clutch?

Bikesmith wrote:Maybe the engine is running fine but it's having to work against another problem? A dragging brake? Slipping clutch?

Hum.. I have done the brakes recently, they don't seems to force on the wheel.
The clutch is brand new, I have changed everything when changing the main oil seal, and it seems to work well.
I don't know how i can confirm it?

ouafnico wrote:

That is not the spark plug; that is the spark plug wire connector that fits on top of the spark plug. In the attached diagram the spark plug wire connector is at the left end of the wire #2. The spark plug is #1 and will have a manufacturer's name and a number and letter combination written on it. You'll need to remove it from the cylinder head to view what is written on it.

Laitch wrote:

ouafnico wrote:

That isn't the spark plug; that is the spark plug wire connector that fits on top of the spark plug. In the attached diagram the spark plug wire connector is at the left end of the wire #2. The spark plug is #1 and will have a manufacturer's name and a number and letter combination written on it. You'll need to remove it from the cylinder head to view what is written on it.

Sorry i'm not always good on english mechanical terms.
Spark plugs are bosch x5dc.
I changed them recently, they got 200km.

ouafnico wrote: The clutch is brand new, I have changed everything when changing the main oil seal, and it seems to work well. I don't know how i can confirm it?

If the clutch hand lever is moved with one finger, when it meets resistance there should be 2.0mm–2.5mm at dimension A shown in the drawing below. That will be the space between the lever and its housing. Careful setting of the clutch lever contact at the clutch piston at the transmission, and free play distance at the clutch hand lever is critical.


If that measurement is OK, run the moto at highway speed in fifth gear then twist the throttle firmly. If the clutch is slipping, the revs will increase but the moto will move ahead slower than expected.

I agree with Point-Seven-five. You should review your fuel efficiency calculation.

oufnico wrote:I've visually synchronized the 4 air intakes

Throttle bodies are synchronized by turning their air screws so they register close to each other when attached to a manometer; they are not synchronized by sight.

Laitch wrote:

ouafnico wrote: The clutch is brand new, I have changed everything when changing the main oil seal, and it seems to work well. I don't know how i can confirm it?

If the clutch hand lever is moved with one finger, when it meets resistance there should be 2.0mm–2.5mm at dimension A shown in the drawing below. That will be the space between the lever and its housing. Careful setting of the clutch lever contact at the clutch piston at the transmission, and free play distance at the clutch hand lever is critical.


If that measurement is OK, run the moto at highway speed in fifth gear then twist the throttle firmly. If the clutch is slipping, the revs will increase but the moto will move ahead slower than expected.

I agree with Point-Seven-five. You should review your fuel efficiency calculation.

oufnico wrote:I've visually synchronized the 4 air intakes

Throttle bodies are synchronized by turning their air screws so they register close to each other when attached to a manometer; they are not synchronized by sight.

Thanks.

I will check the clutch hand lever.

When I say I have synchronized the 4 bodies visually, I mean I use the method explained in my technical review, visually I have review the 4 to be closed/open identically, then I use a depression meter plugged in, motor running, to get the best sync of the 4

Vacuum caps on 1-3 ok?
Correct injectors?
Correct temperature sensor?
MAF operating correctly?
Fuel Pressure Regulator ok and the correct one?

Doesnt say if 2 or 4v engine. Temp sensors are not the same but are physically same.

92KK 84WW Olaf wrote:Vacuum caps on 1-3 ok?
Correct injectors?
Correct temperature sensor?
MAF operating correctly?
Fuel Pressure Regulator ok and the correct one?

Doesnt say if 2 or 4v engine. Temp sensors are not the same but are physically same.

I have ordered 3 new vaccum caps, actual seems quite old.
The injectors are originals, but i didn't find a shop to test them and see if they are regular
The temperature sensor shows good values, but for 30€ i have ordered another one to compare.

What call you maf ?

Fuel pressure regulator is original, and is working, got fuel back on the tank and pressure on injection ramp between 2 and 2.5 bar

It's a 2v engine

ouafnico wrote:What call you maf ?

What is being called the maf  is the air flow meter installed in the air box and connected to the fuel injection control unit. It is #8 in the diagram. If its electrical connector is oxidized, making poor contact or disconnected, or if the vane inside it is sluggish or seized, there will be fueling problems.



 Have you checked/adjusted valve clearances yet? Have you done a compression check of this engine?

Laitch wrote:

ouafnico wrote:What call you maf ?

What is being called the maf  is the air flow meter installed in the air box and connected to the fuel injection control unit. It is #8 in the diagram. If its electrical connector is oxidized, making poor contact or disconnected, or if the vane inside it is sluggish or seized, there will be fueling problems.



 Have you checked/adjusted valve clearances yet? Have you done a compression check of this engine?

Thanks.
I have checked in the past the maf, the little door was opening correctly (no force point).
I just did not verify the connections, on the french forum for bmw they ask me to do not touch it, because is supposed to be configured with some CO2 sensors that I can't have.

The compression of the engine was homogeneous on the 4 cylinders, maybe a little low but correct (above 8.5 bars if I remember correctly)

When did you check/adjust the intake and exhaust valve clearances?

Laitch wrote:When did you check/adjust the intake and exhaust valve clearances?

Some days ago, just before verifying the 4 air intake throttle.

To summarize:

• The engine has 198,000 kms/121,000 miles on it.
  
• Compression is acceptably within specification and balanced in all cylinders.
  
• Valve clearances are correctly adjusted.
  
• Throttle bodies are balanced.
  
• The throttle switch is correctly set.
  
• The throttle body vacuum caps are old and will be replaced.
  
• The crankcase breather tube to the air box has been replaced.
  
• Oil consumption is within specification.
  
• The air filter is new.
  
• The fuel filter has been replaced.
  
• The coolant temperature sensor gives correct readings.
  
• Fuel pressure is within specification.
  
• Fuel is not leaking from the exhaust.
  
• Spark plugs are the correct type and have only been lightly used.
  
• The engine idles and accelerates acceptably when warm.
  
• The clutch has been adjusted according to specification and does not slip under acceleration.
  
• The brakes pads are not creating resistance to wheel rotation.
  
• Accuracy of the Tenet instrument has been verified.
  

The result:
Fuel consumption by the motorcycle in its current condition is claimed to be 10L of fuel per 100km (1gallon per 22.2 mile). The distance figures represent approximately half the average distance that would be considered appropriate for a K100 in good condition and many motos could get longer distances from the same amount of fuel.

What remains to be checked:

• The accuracy of a coolant temperature sensor that already seems to be accurate.
  
• The flow rate of the fuel injectors
  
• The injection signal timing at the fuel injection control unit.
  
• Ignition timing
  
• The air flow meter’s electrical connection and the operation of its vane.
  

If injectors were dumping twice the amount of fuel than is necessary, fuel would probably be leaking out the exhaust when cold and/or the engine would likely be responding with more difficulty than you have described.

Anything else—corrections, additions, deletions, supplications?  
It's time for a maple creemee and some fresh air.

Ouah! What a very detailled summary! Thank you !

Actually yes it's seems correct...
Is there some howto to check the work of the air flow meter? Like resistances values or like?

I will check the accuracy of the tenet next weekend.
I don't know if it's a good idea to get some new injectors, I saw some references on tills.de but don't know if it's going to be better than the originals.

Many thanks for all your help

An alternative would to be have the injectors serviced.

duck wrote:An alternative would to be have the injectors serviced.

Yes... I need to find some professionnal how can check them around.. the bmw original are reparables?

ouafnico wrote:

duck wrote:An alternative would to be have the injectors serviced.

Yes... I need to find some professionnal how can check them around.. the bmw original are reparables?

I've had fuel injectors serviced many times.

More info here:
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/fis/fis.htm

duck wrote:

ouafnico wrote:

duck wrote:An alternative would to be have the injectors serviced.

Yes... I need to find some professionnal how can check them around.. the bmw original are reparables?

I've had fuel injectors serviced many times.

More info here:
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/fis/fis.htm

I'm going to check a pro
I already have passed the injectors in the ultrasonic cleaner and changed the seals and filter.

ouafnico wrote:Is there some howto to check the work of the air flow meter? Like resistances values or like?

Click on the Portal tab on this page. Click on K100 Forum Tech Page in the text. Agree. In the category Electrical, click on the document Troubleshooting The EFI (French). Scroll through that document; you'll find some general values for the meter and many other tests.

Laitch wrote:

ouafnico wrote:Is there some howto to check the work of the air flow meter? Like resistances values or like?

Click on the Portal tab on this page. Click on K100 Forum Tech Page in the text. Agree. In the category Electrical, click on the document Troubleshooting The EFI (French). Scroll through that document; you'll find some general values for the meter and many other tests.

Thank you 

ouafnico wrote:Hi all,

I'm working on a 1989 K100, which is done and running fine, except the fuel consumption.

Actually I'm about 10L for 100km, is quite high.

I've checked a lot of things, but I don't know what to search now...

- All is brand new on the tank, except the fuel pump
- there is correctly fuel returning on the tank where running
- Pressure is above 2-2.5 bar on the injection ramp
- injector are working, but I didn't test them on a specialist, but filters, seals are new, and they did pass in the ultrasonic tank for some time
- depression tube on the 4th cylinder is new
- the little hose between the block and the air filter is new 
- I've visually synchronized the 4 air intakes
- TPS is in good position
- air filter is new

But it seems the bike is always too rich... any idea?

Sorry for the english.


Thanks

If it's a 4V engine check that the over temperature warning light illuminates for a couple of seconds when you turn the ignition on. If it doesn't the engine management "brain" over fuels to prevent overheating. I spent over a year chasing an over rich mixture and poor fuel consumprion due to a blown bulb on the instrument panel. The same warning lamp is used to flash any error codes stored.

mitcher9 wrote:

ouafnico wrote:Hi all,

I'm working on a 1989 K100, which is done and running fine, except the fuel consumption.

Actually I'm about 10L for 100km, is quite high.

I've checked a lot of things, but I don't know what to search now...

- All is brand new on the tank, except the fuel pump
- there is correctly fuel returning on the tank where running
- Pressure is above 2-2.5 bar on the injection ramp
- injector are working, but I didn't test them on a specialist, but filters, seals are new, and they did pass in the ultrasonic tank for some time
- depression tube on the 4th cylinder is new
- the little hose between the block and the air filter is new 
- I've visually synchronized the 4 air intakes
- TPS is in good position
- air filter is new

But it seems the bike is always too rich... any idea?

Sorry for the english.


Thanks

If it's a 4V engine check that the over temperature warning light illuminates for a couple of seconds when you turn the ignition on. If it doesn't the engine management "brain" over fuels to prevent overheating. I spent over a year chasing an over rich mixture and poor fuel consumprion due to a blown bulb on the instrument panel. The same warning lamp is used to flash any error codes stored.

Thanks. In my case it's a 2V

Hi team


I did some check this morning with interesting values 
I have checked the values for the maf on the jectronic connector, according this graph you got on tech page





Actually, i got these :
Pin 5-7 : 61
Pin 7-8 : 330
Pin 8-5 : 361
Pin 8-9 : 212 (22°C)

First value seems low ? And last quite high?

All other on the jetronic seems good

Because the engine is starting well and those value discrepancies are linked to hard starting, I'd move to testing a different component right now. What are the resistance values of the primary/secondary coil terminals? Are the spark plugs sooty after a typical ride on the Brick?

I will check the resistance of them tomorrow, and check for cracks.

The spark plugs are black.. and seems oily.




By the way I drove today, it runs well and smooth (pushed to 6500rpm).
And the tenet is good for the odometer.

No cracks on them.

Got 2.3Ohms to the primary coil on both.
Got 12.85 kohms on the high voltage terminals for first (1-4 cyl)
And 12.63 komhs for the second (2-3 cyl)

You seem to indicate the FICU values are within specification so evaluating fuel injector function would be next.

. . . and the spark plug wires themselves.

Laitch wrote:You seem to indicate the FICU values are within specification so evaluating fuel injector function would be next.

Thank you.
Maybe I can see if I got 4 little bottles, and try to make the 4 injectors spraying on them to see if they are similar... 
Or I need to find a professionnal here to check them.

Laitch wrote:. . . and the spark plug wires themselves.

How can they influence the consumption ?

They need to transmit sufficient energy for efficient combustion of fuel.