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