Cesar, your motorcycle most certainly has a problem.  The engine in my old K100RS was just waking up at 4.5 k rpm.  Yours should continue building power to redline.  
What have you done to correct this?  What do the spark plugs look like?  Does the engine seem to run smoothly, or does it have significant vibration?  What about the timing?  Is it properly set? Did you measure compression in the cylinders?

If the engine was rebuilt, did it perform as it should immediately after that work? Or, is this problem that suddenly arose only much later?

The only problem I ever had with my K100RS was caused by the plug on the left front underside of the tank - the one that provides electricity to the fuel pump.  It would sometimes make intermittent contact that stopped the fuel pump.  Some replace that troublesome connector entirely.  I solved my problem with some cleaning of the contacts and stretchy silicon tape.  

César Santos wrote:What can I analyse?

The list of systems to analyze is a long one. Start with the most simple. Can you describe how completely the moto was disassembled for inspection by the mechanic?

When you twist the throttle grip, you should feel immediate tension as the grip engages the cable. Look at the throttle bodies. 

The throttle cable connected to the throttle grip also connects to a rotating mechanism between two of the throttle bodies. Twist the throttle grip or push the disk with your finger to determine whether some part of the throttle bodies is obstructing the mechanism's rotation, the cable is faulty, or if the mechanism needs lubrication. Sometimes, one of the clamps on the rubber tubes on top of the throttle body next to the throttle cable mechanism will be installed in a way that blocks full rotation of the throttle cable mechanism.

Check those items and tells us what you discover.

Have you checked the ignition timing?  The Hall Effect sensors are mounted on a plate at the front of the engine.  The plate can be rotated so it aligns with an opening in the cover it is mounted in.  If the timing is off, it can be difficult to rev the engine beyond a certain point.

While I've never heard of it, I wonder if the rev limiter is acting up. It does seem odd that the engine won't rev past 4500 rpm which is approximately half of the rev limiter setpoint.

Hi,
I have same problem with my K1. Lost of power above 5000rpm.
It seem to help if pump the throttle at high rpm. It feels like it is lacking fuel.
I have just done top end over haul with new Rubber hoses and tubes.

No not yet. Just did the first drive after overhaul. Might be fuel or timing issue. Going check these next week..

I alluded in Reply#4 of this thread to this condition possibly being the cause of dismay. Take a closer look, really close. 

Laitch wrote:I alluded in Reply#4 of this thread to this condition possibly being the cause of dismay. Take a closer look, really close. 

This something to look at. Thanks!
When I took the cylinderhead of I had ziptied chain to sprockets, bu have little suspicion that I have stuck chain tensioner.

Laitch wrote:I alluded in Reply#4 of this thread to this condition possibly being the cause of dismay. Take a closer look, really close. 

This is it, your were right! It does hit those clams..

Boa tarde


Eu continuo olhando, a moto funciona impecavelmente, mas 3/4000 rpm parece ser o seu limite. Na 5ª marcha vou a 3rpm a 80Km, acima disso treme muito e para chegar a 110/120 parece além do seu limite.
Tenho tentado perceber o que é e qual é o comportamento e as velocidades deste tipo de motos, sei que não são muito rápidas, mas certamente algo não está certo.
Você pode me ajudar com o problema de temporização do motor? como posso verificar?
As velas de ignição e cabos, existe algum teste a ser feito, quando é melhor comprar novos?

Obrigado

I doubt it's a timing issue. The Hall Effect Sensor is secured by two screws and I've never heard of an HES coming loose and altering the timing. When the notch on HES is aligned with the notch on the block where it mounts the timing is correct.



 

Another thing: Has it sat unused for a long period of time? Over time old gas in fuel injectors can dry up and turn to varnish which clogs the injectors. This restricts the maximum fuel they can deliver. Whenever I get a K bike I always have the fuel injectors serviced.

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

Put your bike in your signature - year/version and VIN if you like so people trying to help know what you’re looking at.

Have a look at the TPS, the little black box at the end of the throttle plate shaft, to see if it restricts or switches to full throttle mode?

Cheers, René

My bike is an '86 K100 LT.

Today I made a small trip of 80Kms, what is really noticeable is the vibration as mentioned above.
I'm going to buy new spark plugs, the bike starts very well and works very serenely, I don't think so.
Then I go to the injectors, from the outside they have some corrosion...
Engine timing seems fine to me... photo attached



Thanks

You can get a lot of vibration and knocking from injector issues.

If you have done a lot of work check that injector connectors have not been mixed up, the bike will still run but badly. If 1 and 2 got mixed up, or 3 and 4.

Good afternoon,


And how can I understand? just testing?

Thanks

César Santos wrote:And how can I understand? just testing?

Você sabe usar o Google Tradutor? Você sabia que existe um manual neste site que explica como sua moto funciona, como testar os componentes da motocicleta e o que indicam os resultados do teste? Estou fazendo esta resposta usando o Google Tradutor. Eu espero que você entenda.

Good afternoon,

Where can I find this manual? I am not finding...

A link to it is in the Portal. The Portal tab is at the top of this page. The information is in the Tech Page. Its title is Troubleshooting the EFI. Here's the link to the Tech Page in the Portal. Click on I agree. The guide is near the bottom of the Electrical section.

I had a  problem on my 86 K100, I cleaned the contacts on the rheostat in the airflow meter

Do we know how much overhaul was done?

Or what components were replaced?

Eg temperature sensor possibly replaced with a 16v one? Or mounted in ptfe tape?

Or fuel tank lines incorrectly connected?

Correct plugs [non resistor type]? Plug bobbins?

Plug leads replaced with 16v leads?

Good morning

I don't know the history of the bike, I just know that it was serviced at BMW, as I have the invoices for the service.
I've already bought new spark plugs, this weekend I'll replace them. The cables look like the originals...
How can I tell if the temperature sensor is 16V?
Thank you for your help

Good,

I've changed spark plugs and everything is the same.
I still think that the has a lot of vibration and little speed, out of curiosity, what are the speeds of these bikes?
Is it normal at 130K/h or does it feel like it's coming to an end?

Your bike should not vibrate and should do 200km/h, mine does. 

If your bike remains unchanged with cylinder one injector disabled, that's a problem. Same with any of the other cylinders.

César Santos wrote:Good morning

I don't know the history of the bike, I just know that it was serviced at BMW, as I have the invoices for the service.
I've already bought new spark plugs, this weekend I'll replace them. The cables look like the originals...
How can I tell if the temperature sensor is 16V?
Thank you for your help

What spark plugs did you buy?

Maybe I should have said, does one of the header pipes seem colder than the others.

Good morning,

Spark plugs are NGK D7EA.

César Santos wrote:Good morning,

Spark plugs are NGK D7EA.

They should be good, I have them in my 2v Ks. Are the threaded tops exposed or have they the bobbins on them?

The plugs have the tops with the thread showing or opposite to the old ones. It makes a difference?

The cables are placed with the 4th being the cylinder at the front of the bike and the 1st being the cylinder closest to the center of the bike, is that correct?

92KK 84WW Olaf wrote:

César Santos wrote:Good morning,

Spark plugs are NGK D7EA.

They should be good, I have them in my 2v Ks. Are the threaded tops exposed or have they the bobbins on them?

a.k.a. terminal nuts



I don't know why NGK does not include terminal nuts with the spark plugs. Other brands do.

César Santos wrote:The plugs have the tops with the thread showing or opposite to the old ones. It makes a difference?

The cables are placed with the 4th being the cylinder at the front of the bike and the 1st being the cylinder closest to the center of the bike, is that correct?

No 1 is at the front of the bike, no 4 is at the back.

But for plug leads it is ok, 1 and 4 fire together, 2 and 3 fire together.

The front coil on left as you look at them is for 1 and 4, the rear coil, on right as you look at them is for 2 and 3.

But having the threaded top showing is not good. Problem here and may be your problem too.

You need the terminal nuts, we call them bobbins too. If your old plugs are NGK D7EA you can unscrew them and put them on the new plugs. But if your old ones are Bosch or Beru they are formed and do not unscrew.

If you need terminal nuts, you can get them at a shop that services small engines for things like pumps and lawn mowers.  They usually have a few old plugs in a bucket that you can take the nuts off of. 

You can also contact your country's NGK distributor and ask the tech support people for a dozen.  They mailed me an envelope with them for no charge.  If enough owners bothered them, NGK might start including them with the plugs.

So I have the cables changed, but it is indifferent, but I will change.
The old plugs were Bosch, the tops don't come off, but I'll bring them tomorrow and give feedback.

Thanks again, it's a pleasure to have your help

Are the spark plug wires for Cylinder 1 and Cylinder 4 attached to the forward ignition coil and the wires for Cylinder 2 and Cylinder 3 attached to the rearward coil?

Good...


I already put a coil on the spark plugs and managed to get some injectors from a K100 to try, all the same...
It's not all bad, we can exclude these two points.
Is it the MFA? or could it be valves, are these adjusted?

Thanks

Good evening everyone

The saga continues, I sent the bike to the mechanic again, the engine point was checked, the valve clearances, cleaning and fuel synchronization were checked, everything was ok.
I had already installed new spark plugs and injectors.
The bike continues to work perfectly, starts very well and behaves very well up to 100kmh, above that speed it shakes and taking it up to 130kmh seems to exhaust the engine and its rpm does not exceed 4500/5000.
I start to despair...
Tomorrow I'll check the ignition coils and I'll check the spark plug cables.
Do you know how to check the ignition cables?

I'm running out of solutions...

Thanks

César Santos wrote:Good evening everyone

The saga continues, I sent the bike to the mechanic again, the engine point was checked, the valve clearances, cleaning and fuel synchronization were checked, everything was ok.
I had already installed new spark plugs and injectors.
The bike continues to work perfectly, starts very well and behaves very well up to 100kmh, above that speed it shakes and taking it up to 130kmh seems to exhaust the engine and its rpm does not exceed 4500/5000.
I start to despair...
Tomorrow I'll check the ignition coils and I'll check the spark plug cables.
Do you know how to check the ignition cables?

I'm running out of solutions...

Thanks

try cleaning the wires on the rheostat in the air flow meter

Have you replaced the fuel filter?

Good morning

No, I did not perform any maintenance on the fuel system.
When I replaced the injectors I tested them out and everything seemed fine.

Thanks

César Santos wrote:I'm running out of solutions..
I did not perform any maintenance on the fuel system.
When I replaced the injectors I tested them out and everything seemed fine.

You are far from running out of solutions.

Everything seemed fine at idle and low speed until you tried to ride the Brick at high speed. High speed completed the test, showing everything was not fine. As Rick G implies, a partially blocked fuel filter will reduce engine performance at speed. That filter should have been replaced as soon as you bought your motorcycle. All the fuel tank's interior hoses should have been replaced, too.

You have written that your motorcycle was overhauled more than two years ago. It does not appear that the overhaul included cleaning electrical ground connections.

At this time, one point seems clear to me. Your mechanic should have located the problem by now. From your description of outcomes, your mechanic seems to be without sufficient experience, or time, to diagnose the trouble in your K100. That is not unusual and is one of the reasons why forums like this one have been created.

The problem many purchasers have when buying a used classic K-model motorcycle is their belief that the outcome will be the same as buying a used car. A used car's engine systems are somewhat protected by sheet metal or insulation. A used K100's components are much more exposed to harsh weather conditions and condensation. Because they have some protection, a used car's systems seem to degrade slower than a used K100's systems so if they are neglected under the same conditions for years, a neglected car has a somewhat greater chance of functioning sooner when reclaimed than a neglected K100 has. The K100's electrical components can function well bashing along on a potholed, rut-filled road but they are sensitive to neglect. Engine performance will almost certainly be negatively affected by oxidation created on their electrical connections while being neglected in storage.

The troubleshooting manual at this site and the other manuals I have for the K100/K75 series indicate that electrical ground failures and faulty electrical connections in general are one of the most common reasons for problems with engine performance. I have witnessed performance failures being eliminated simply by tightening ground connection screws or re-coupling electrical connectors. The attached photo shows me that you have much work to do reclaiming this old Brick. Right now, the easiest significant ground connection to clean is the battery ground cable connection circled in the photo. That means removing it from the transmission, then using a wire brush or wheel to remove oxidation from the attachment point on the transmission, the bolt, the washer and the terminal at the end of the cable. The assembly must be immovably tight when reconnected after cleaning. Also inspect the bolted components at the cable connections of the battery itself.

Once that has been completed and you've road-tested the Brick afterwards, you should remove the fuel tank and clean all the ground connections at the main ground connection plate on the backbone of the frame. That work includes using a wire brush to clean the bolt, the plate and all the wire terminals that attached to the plate. The frame connection to the transmission on the brake side of the motorcycle as should be cleaned. That is discussed here. All electrical connectors of the wiring harness, including the ignition control unit plug and the fuel injection control unit plug connections, should be cleaned using electrical contact cleaner and verified to fit tightly together.

You could have other problems that if corrected might restore full operation. You have not indicated that you have checked fuel pump delivery pressure, the function of the coolant temperature sensor, or the resistance of the coils yet. Maybe even divine remediation of faulty engine performance will occur; however in absence of that, there's no denying the following point, César: If it hasn't been done already, you should complete all electrical component inspection and cleaning to have the greatest chance of your motorcycle's performance being reliably improved. 

Be patient; your motorcycle has been malfunctioning for only two years. Como se costuma dizer, o tempo voa.

Hello

Yes, my mechanic, despite his customers being mostly old BMW and Japanese motorcycles, the bike has been there twice months with the same complaints and there was no solution.

I will clean all ground cables that I identify and apply contact lubricant to all fittings.

I just don't dare touch the fuel filter, I'll have to ask the mechanic, another mechanic.

I have already tested the coils and they seem fine, although I found two wires that caught my attention, can you help me?

César Santos wrote:I just don't dare touch the fuel filter, I'll have to ask the mechanic, another mechanic.
I will clean all ground cables that I identify and apply contact lubricant to all fittings.

Replacing the fuel filter on your Brick is one of the easiest tasks to do, if your hands fit into the fuel tank opening, but no smoking is allowed. duck, a member here, has it all laid out for you in this document.

What type of contact lubricant are you using?

How did you test the coils? Why did they seem fine?

How many thin wires are attached to the terminals on the bottom of the coils? What color are they?

What color are the wires in the photo above? If they have stripes, what color are the stripes?

Rick G wrote:Have you replaced the fuel filter?

The problems you describe are classic for a almost blocked fuel filter.
https://www.kforum-tech.com/forum-area/__Files/mechanical/k%20fuel%20filter/K%20fuel%20filter.htm

Good morning


The coils gave the values 2.6Oh and 12.5Oh according to the manual, I did a night inspection and didn't see anything abnormal.

I've already ordered the gasoline filter, when I replace it I'll give feedback.

As far as the disconnected wires are concerned, they are brown, I would appreciate it if you could tell me where yours are connected.



The contact lubricant I use is WD40 contact cleaner.

Thanks

That is possibly your problem; it looks like someone has been messing with the earth connection and has put a braided cable on them. Check the brown wires for continuity to the battery earth.

Under the coils, the wires should be connected as below:

Brown (earth) to pin 31
Green/yellow (power) to pin 15
Black/blue (output 1 and 4) to pin 1
Black/red (output 2 and 3) to pin 1

Black/blue also supplies the signal to the RPM counter.

Good afternoon
Yes, there is a cable connecting both coils to the ground point as shown in the photo:



Can you help me with the pin issue? How do I know which are 31, 15 and 1? Can you provide me with some photos of the correct connection?

Thanks