Hi,

I have '85 K100RT and I'm experiencing a lot ot problems.

Before I changed the fuel filter the bike starts and then stalls - It was broken filter thus lean mixture. Sparks colour prooved that.

Then I replaced the fuel filter with new OEM and cleaned the injectors /not flow tested/. Now the mixture is very rich /all plugs are so foulded, that fuel flows outh of them/. Howewer the bike starts and after a few seconds stalls.

I have checked the temp sensors, air leaks, pump, fuel house return valve.

Is it pssible to be the EFI, or just all the injectors are gone bad after cleaning?
Regerds,
Ivo Markov

Hi Mark,
I would be looking at the regulator [rear of the fuel rail]. a replacement is probably required.
I had similar problems and removed the regulator.I blew air in one port them the other and replaced it. All was then OK to date.
Another mod is to remove the tube from the 4th cylinder which is the vaccum tube to the regulator and cap it as the other 3.

I like the look of the tube there as authentic so I pushed a small ball bearing up the tube to block it off.

You will get the answer here eventually if that doesn't work.
Ajays.

Hi Ajays,
I've read quite a bit here about the fuel pressure regulator. So am I correct in my understanding that it can be taken out of the loop completely ? If so, what are the issues with not having it, as almost every EFI system I know of needs a regulator.
I have already disconnected the throttle position switch and have a much nicer bike when backing off into tight bends, especially 2-up. Far too much engine braking for my liking with it connected. But is the issue of the wide open switch (richens mixture ?) not being operational a problem ?

Regards,
Dennis

Thanks for the responses.

Let me clarrify a bit. When I installed the cleaned injectors I noticed that the valve in the fuel tank is clogged. I found it because the mixture became too rich and I was looking for the cause. I assumed that the higher pressure in the rail was one to blame. I fixed the valve and now the fuel flows back to the tank, so the pressure regulator keeps pressure below the fuel pump's security pressure relief valve. However the mixture is still too rich.
The two possibilites I see are:
1. All the injectors gone bad, due to the cleaning. This is less possible, all four injectors to fail.
2. Injection Control Unit mailfunction and keeps injectors open too long.

I checked the radiator temp sensor and saw that it gives higher values than normal but it's ressistance drop as expected as temperature rise. In order to eliminate this possible cause I used a 2k/1k/0.3K resistors, directly connected instead of the sensor. The TPS is removed and I also had two airflow meter valves and tried switching them.

The interesting was that the problem occured when I remove the oil cap while bike was running. Then the engine stops due to the leaner mixture and the problem occurs for the first time. This was before I found the broken fuel filter. I think It was just a coincident.

While the bike running If I try to open the trottle it dies instantly!

here is a little problem experienced by my brother (last week)
He had just finished doing cosmetic work on the bike and took it on the road after almost 6 month in the garage.
When he stored the bike at the beginning of the winter, it was working very well but last week it ran like crap.
The bike started well and was running on the idle but as soon as he opened the throttle, the engine was knocking and running like crap until it reached 4500rpm and gas was leaking in the exhaust pipes
The spark plugs were black and fouled.
The solution to the problem was very simple. He had fitted his fuel lines with quick couplers, and the one on the return line was disconnected. Other than the symptom of burning a lot of gas and having the spark plugs fouled, it was a very noisy fuel pump.
The problem is that the engine was running with 65psi of gas pressure in stead of the 36psi required.
The pressure relief valve (on the back of the throttle body) was working, but the return to the tank was blocked.
The fuel pump has one relief valve set to open at 65psi and the main relief valve reduce the pressure to 36psi.
What I would do is disconnect the return line and hold it over a container to see if you get some flow out of it.
If you have some flow when the bike is running (and hopefully the engine runs better), you should look at the return valve in the tank.
If nothing comes out of the return line, you certainly have a bad external relief valve.

Hope this may help, and let us know the result of your investigation.

Bert

I already said that the return valve in the tank was clogged but I cleaned it. Now I can see clearly a large amount of gas flowing back to the tank. This mean that the fuel regulator is working and dropping fuel pressure under 65PSI. How much I still don't know...

Thanks anyway!

As soon as I revieve fuel pressure measurment tool I ordered this week, I will see what PSI the system is on. However in my case I don't think the pressure is the problem.

Did you read one of my previous posting where I experienced an overflow of fuel in the cylinders and found that the problem was a bad connection of the EFI computer?

Unfortunately it's not a loose connection. I cleaned contacts and also tapped the computer in order to expose eventual bad connections inside.
Later I'll try to examine connections of the EFI.

I now remember that before the problem occur I experienced something like missfire on low but above iddle RPM sometimes. I thought that it is plug missing spark or cable problem, but it might be the computer starting to fail back then. The MPG was also a bit higher...

So I'll try to find place here in Bulgaria where injectors can be flow tested and if they are ok, then EFI module shoud be the trouble maker.

The TPS is fitted to prevent back-firing and you have disconnected it.

I would have a good look at your temp sensor. You say that the resistance is higher than normal, this would have the ECU react as if the bike is still (very?) cold and enrichen the mixture.
The amount of fuel injected is predominantly dependend on the air mass meter and the coolingwater temp sensor. The temp sensor has to be right and the AMM can be adjusted with the by-pass screw (which is what you do when you adjust the bike for the mixture ration).
This bike uses various sensors for adjustment, which work with small signal strength. Therefore every dirty connector in the system will affect the operation.
It might be that the injectors are doing the right thing - injecting the amount that is determined by the ECU on the basis of the sensor information.

Hi,
I very strongly suspect Rene has given the answer here, our bikes work very well when all sensors are operating correctly, the two sensors - air sensor and water temperature sensor affect the amount of fuel going in as does the flow meter as the throttle opens. Bad earths and dirty contacts will cause a problem, clean all contacts after getting the sensors with correct readings.
Regards,
K-BIKE

Dennis wrote:Hi Ajays,
I've read quite a bit here about the fuel pressure regulator. So am I correct in my understanding that it can be taken out of the loop completely ? If so, what are the issues with not having it, as almost every EFI system I know of needs a regulator.
I have already disconnected the throttle position switch and have a much nicer bike when backing off into tight bends, especially 2-up. Far too much engine braking for my liking with it connected. But is the issue of the wide open switch (richens mixture ?) not being operational a problem ?

Regards,
Dennis

Dennis, just to clarify. Pressure regulators on L-Jetronic systems do two things:

<li>a. regulate the pressure at a constant level, in our case 36psi. This is done internally via a spring, diaphram and a ball valve. This is essential and is a constant set by Bosch, and

<li>b. Our systems use vacuum to modify the pressure (a bit, by a few psi) depending on the load (vacuum level). They do this by sucking on the air space above or below the diaphram. You can disconnect this because the bie seems to run better without vacuum vibartions. You need to experiment to see if this works for you.

However, you can not disconnect the regulator. If you do the pressure will be well above the specs and the thing will run very rich if at all.

Well said! The vacuum line is intended to ensure the fuel pressure is always at the same at the injectors, corresponding to the pressure behind the throttle plates. This is supposed to make sure your spray pattern is always the same.

Hi again,

Thanks for all the responses.

Temperature sensors, both air and cooling liquid, are eliminated as a problems.

I used resistors instead cooling liquid sensor, I tried 2k, 1k, 0,3k. According to this

I set temperature that should tell the computer to lean the mixture. Also the temperature sensor that I'll replace today isn't that bad, It is 5,7k at 20C and drops with temperature growing up. I also checked for loose connections here, by examining resistance between two contacts of the connector to the sensor. There was a low value that tells me cables are OK, and there is connection on ECU side.

The air temperature sensor is also out of suspicion because I have two airflow meter valves that I switched and no change. Also, according to this

If there's loose connection on this sensor It should lean the mixture.

However, today I'll get new BOSCH temperature sensor and will change it anyway.

Regards,
Ivo

Ned,
Thanks for clarrifying about the purpose of the fuel pressure regulator. My brain must have been clouded, of course the reg sets the predetermined pressure (by the spring) then the manifold vacuum varies it slightly.
Too concerned about lubrication issues I guess.

Regards,
Dennis

Dennis wrote:Ned,
Thanks for clarrifying about the purpose of the fuel pressure regulator. My brain must have been clouded, of course the reg sets the predetermined pressure (by the spring) then the manifold vacuum varies it slightly.
Too concerned about lubrication issues I guess.

Regards,
Dennis

About the Fuel Pressure Regulator: When you open the throttle the vacuum under in the intake drops and this makes regulator to increase the pressure thus making mixture a bit richer. This acts as like a accelerator pump on a carburettor car.

Ivo

Yesterday I checked all connections to the EFI and all seemed OK /from Airflow Meter Valve, Temperature sensors and so on/. I also checked both Starter and Load shed relays and they are fine.
I'm running out of theories... All points to EFI or injectors failure...

Tonight I'll try to locate something else on installation but It seems I have to order new EFI computer.

Ivo

Nop, all electical connections are in perfect order. Today I'll pay for a new EFI computer so in a week or bit more I'll know for sure.

Ivo

Try what i did, take plugs out, dry them out, turn over the engine a few times with everything out. When there all dry put them back.

I did this and it all started, i also had the non return valve stuck so fuel wasnt returning and was overfuelling. all worth a try?

I tried that with few differences - left the bike with spark plugs out for a day, so that all fuel from the cylinders evaporate and changed spark plugs with old ones that were fine and almost new. That unfortunately didn't help.

I also need new windscreen and I'm thinking about this one:
http://www.motorworks.co.uk/bmw/products/product.php?f=i&code=BA_15_40_VA_30&shnew=New&model=K75/100/1100&shnewcode=15∂=Screens+and+parts&sub_part=Screens+K100RT&modelcode=40&partcode=VA&source_code=BA_15_40_VA_30&header_text=&header_text_image=0
/the clear one on the top of the list/

Can you recommend me something else?

You said the air temperature sensor was 5.7K? = 5,700 Ohms? that is very high as at 20 C it should be way lower about 200 ohms.
I can't see anywhere you have measured the fuel pressure is it 36 psi?
What compression do you have? Check with the throttle wide open all plugs out, turning over on the starter with ignition coil inputs disconnected so no spark is generated.
Regards,
K-BIKE

Hellow guys, after a year and even more I have some progress.

The bike was for six monts in our BMW dealership here in Bulgaria, and the result was melted harness, a lot of scraches over the paint - a lot of regress actually. When I took it the bike won't even start. They were saying that both ECUs I have are bad and are not controlling the injectors.

What I have acoomplished before I gave up the bike to BMW was:
New secondhand ECU
New secondhand CDI
New teperature sensor
New airflow meter valve
Messured fuel pressure

There is no need to say that everything was working as expected and still I had no clue. The Hall sensor were giving the signal back to the CDI, the ECU was driving the injectors, but why I had so much fuel, I had no idea.

So after I took my bike from the BMW, I was more radical. I slowly and carefully took all harnesses (three parts) down, and reconditioned them. Then I put everything back together and I progress to the previous level - too much fuel.

There is no need to say that I didn't want to touch the bike again soon, so I decided that I need different opinion, but not from the official dealership. I gave the bike to a mechanic that was recomended as capable with engines and electronics.

Meanwhile I even open one of the ECUs to see what's inside - 3 transistors in working condition and all other parts can still be found and replaced. At least that's what a guy repairing TV's and all other kind of electrical appliance told me.

So now bike starts, and interesting was that the one to blame seems to be the HALL sensors - at least one of them, to be correct the "badass" one.
My conlcusion that they were OK, at least at room temperature, is that I got signal from them to CDI, and from CDI to ECU, and I had a nice spark on 4th cylinder. WRONG! I dind't check cylinder 1 and 3 - they are controlled, obviously, from the "badass" hall. The other one is used from the ECU to signal the injectors, which all open at once.

I managed to borrow working Hall sensors from a friend and the bike is now running. I'm still afraid to say that's fixed, not to curse anything.

But ofcourse all good things come together with not so good ones.
The bike is now smowking hardly in gray, and 20 minutes was not enough time to clear it. It also has 15atm (all) compression which may be because of seized oil segments. The front forks are leaking, despite the fact that I replaced everything before the problem occur. Also the bike is repainted, but I need to buy many small parts that was lost when I took the bike, and also all BMW emblems that were tooked down when repainting.

This sunday I hope to take it back (300km away) on a trailer, and I plan slowly to restore it over the winter.

Keep Your fingers crossed, that the bike did all the bad tricks from its bag, and won't fool me anymore!

good luck markovivo !!! happy days ....enjoy your ride

Thanks,
just waiting for the snow to enjoy... winter sports. Not exactly road motorcycle riding time here, maybe some dirt/mud riding suits the cold weather more.

Sunday, as it's the day that I'll pick my bike, seems so far away...

Hi guys,

I took my bike from the mechanic and had the time to write about the progress. Here's the bike after the 6 hours trip on a trailer back home:



The compression of the cylinders is still high, about 13 and I hope it'll drop down to the specified 10, otherwise it's possible to have to repalce the piston rings.

From the moment I bought the bike the throttle wasn't moving freely. I checked the mechanism:





The lubrication didn't help but revealed the problem - throttle wire was bad:


It was fixed by a local company - replaced the cable and bottom half of the cable housing:


Exept the gray (comming from burning oil) smoke, I supposed a bit reacher than usual mixture. The spare airflow metter I had was oppened so i tighten 2 teeth on the spring. This gave bit more tension than my original airflow meter - one tooth is enough to make them equal, and I put one to respect the age . I put the spare one in the air filter case. I'll correct precisely the mixture later.


Then I installed the airflow box:




The ECU (brain):


The button controlling lights on the right console wasn't moving freely so I gently put the console appart. There are a lot of small parts, so You should be careful not to loose something:



Then, I reassemble some of the plastics to test the bike:










Aftermarket screen, I bought several months ago:




Spark plugs cover:


The bike run with the borrowed Hall sensors and I did 2km test ride. The bike was running smoothly, so I was happy.

I decided to finally test the blamed Hall sensors::


Here is the two sensors on the plate:


After some test I saw that the sensors were givving correct signals below voltage 10-11V:


After that, one of them is giving 1V signal no matter if it's closed or open. Here You can see that it returns only 1V, despite the fact that it should return the supplied voltage ~12,2V:


This one is working correctly:


Placing a metal oblect should result in no signal:


The defected one is again returning that bad signal ~1V:



This may result in two of the spark plugs not to be working at all.

Yesterday I had the chance of having sunny and relatively warm weather (5C), so I rode the bike still not fully dressed, about 40km. It was running smooth, and the smoke has gone. Only a bit when revving hard, probably still a bit rich mixture. Here is some short video of that bike autumn ride:

https://www.youtube.com/watch?v=uH7KeFaQBBo

This is for now.

Thanks everyone! I'll post some information when I complete the restoration, or if some problem comes up again.

Well done Marko and good pictures.
Regards,
K-BIKE

great work marko ....starting to look better and better

Hi everyone,

Just a few updates - Bagster, fork gaiters, other parts like BMW eblems, voltmeter, ignition timing and so on:











Bike is running well, except that is a bit rich at idle but that's because of the air bypass valve being stuck. Fuel consumption is about 5,2-5,5l/100km.

Of course, when not having problems I create one myself. So here is what I noticed:



Do You notice something wrong?

... like the readline not beeing where it should be.

Take a look at this little black devils (ignition units):



(right one is the original, left one is second hand from e-bay uk)

So I didn't know that there were power restrictions for some countries, but obviously there were - mine is from Switzerland. Top speed when the ECU shuts of the injectors is 190km/h.

I'll change the ignition units in near future and I'll see if this will be sufficient for the removal of the restriction.

Regards,

Ivo Markov

good work marko ,,,i like your testing and conclusions

bike is really starting to come together .....thanks for the update

cheers from down under !!!

˙pɐǝɹ oʇ noʎ ɹoɟ ɹǝısɐǝ s,ʇı os 'sıɥʇ ǝʞıן buıʇıɹʍ ɯ,ı

¡sʞuɐɥʇ

But you should have put it the correct way Charlie often stands on his head in the corner for relaxation.

markovivo wrote:˙pɐǝɹ oʇ noʎ ɹoɟ ɹǝısɐǝ s,ʇı os 'sıɥʇ ǝʞıן buıʇıɹʍ ɯ,ı

¡sʞuɐɥʇ

Like the DaVinci code it's got the makings of a Dan Brown Novel...."The Markov Code"

The charachters:

The Illuminatti - a bunch of amateur auto electricians who are determined to repair small fiddly switches and fit relays to headlights.

The "K"nights of the roundel table - a bunch of old guys who sit around their PC's talking about K bikes.

I wonder if Dan Brown would be interested .



Sorry for the Hijack, I'll go back to sleep now!

Good Thread Ivo, I really like the Bagster. Was it an Ebay purchase?

88KE

I got the Bagster cover from the BAGSTER factory, through one local dealer - 90EUR. It was made by order, so I waited a month or so.



The color almost matches the paint.



Ivo

[/quote]

Like the DaVinci code it's got the makings of a Dan Brown Novel...."The Markov Code"

The charachters:

The Illuminatti - a bunch of amateur auto electricians who are determined to repair small fiddly switches and fit relays to headlights.

The "K"nights of the roundel table - a bunch of old guys who sit around their PC's talking about K bikes.

I wonder if Dan Brown would be interested .



Great post by the way Marko!
My whippet has a winter jacket like your BAGSTER- now there's an idea!
Best
Dave