Hi guys!

So I have a 1991 K100 2V model, which stayed on the cough for the past year and it came up with a cold

I will do my best to describe the problem but I'm also including a video which I shot yesterday in which you can better see the problem along with my 'best' comments.

So for the past 10 years or so the motorcycle worked great. Not even a problem I may say... However, it stayed untouched for like an year or so and when I tried to ride it, a problem appeared.. 
First of all, I think it was a starting problem, since it didn't start very good (it used to start exceptionally even if I hadn't started it in a long time). At first I tought it was a battery problem, so i bought a new one. However, this was not a problem. Even with the new battery it took me like 10-15 mins to start it up. The starter motor works ok, however it doesn't start that good. 
For example, if I'm trying to start it today, it takes like 10 mins to start it. After I start it, if I'm shuting it down and wait for a few mins, or if I'm trying to start it multiple times in like 1-2 hours, it starts ok, but if I'm starting it the next day, it again takes like 10 mins to start it.

But this is not the major problem, however i think it might be related to it.. 

The major problem is explained in the video attached, and along with it, i will also try to resume here what i tried to do to solve it...
- i changed all the spark plugs with new working ones
- i changed the spark plugs wire in between eachother to check if any of them is broken, and I don't think there is any one broken, since they work OK on the working cylinders
- i changed the gas it had from the last time i started it (like an year ago..) by putting new gas in it
- i cleaned the air filter (however it was in an impeccable condition even before the cleaning)
- i tried to clean the gas filter (fuel filter) -- *
- the coils don't seem to have any problem, since the spark wire are giving "sparks" (you can see in the video)

* (fuel filter) - i tried to clean it with the air compressor. And I also tried to blow into it. However, when blowing, i felt a very very high resistance. I don't know if it is supposed to be having this resistance or not, but it was really hard to blow into it. The air passed through, however, tooking high pressure power from me to pass through.

So that's basically it.. The motorcycle was working great last time (a year ago) when i started it. It used to work very smooth and no problems showed in the video were happening... Nothing happened in between. It just didn't want to start and work as it did after this year of 'staying'. 

Has anyone else faced this problem? Do you guys know what it could be? I really want this to work, i have big plans for it 

Here is my video: 


Thank you!

Hi  THE FUEL FILTER is faulty fit new one best of luck

moriarti wrote:Hi  THE FUEL FILTER is faulty fit new one best of luck

Yep just about certain

Get a new fuel filter.

Hi, thanks for the information!

So can the fuel filter be the cause of this problem? If so, why just one cylinder has the described problem?

Thank you!

What does the inside of the tank look like?

What spark plugs did you put in?

My thoughts are on the fuel filter too but the filter basket that is located under the fuel pump could also be an issue. You need pump out to check that. The basket filters fuel on the way into the pump so if it gets clogged the pump is basically sucking air, the pump then pumps fuel through the fuel filter and into the injector fuel rail.

Is there any risk of water being in the tank?

katsawa wrote:Hi, thanks for the information!

So can the fuel filter be the cause of this problem? If so, why just one cylinder has the described problem?

Thank you!

A one cylinder problem is going to be related to that cylinder only. Is one cylinder losing spark or no fuel?
Cylinder 4 plug cap should not be sparking like that. Bad plug lead? If it is no 4 on its own then more likely to be plug lead than coil. Swap no 1 and 4 leads on the front coil and see if problem moves from no 4 to no 1.
What plugs have you? Have they bobbins on them?

Your fuel cap in on wrong way round. That can let water into the tank.

No, there is no water into the tank. I emptied the tank completely when i removed and tested the fuel filter. Then i just added gas. 

Regarding "Is one cylinder losing spark or no fuel?", I'm not sure, but i think it loses fuel, not spark.


Hope you got the chance to watch my video I referenced in the topic. It seems the plug wire gives sparks to the sparkplug, however, the cylinder doesn't seem to be working.

92KK 84WW Olaf wrote:

katsawa wrote:Hi, thanks for the information!

So can the fuel filter be the cause of this problem? If so, why just one cylinder has the described problem?

Thank you!

A one cylinder problem is going to be related to that cylinder only. Is one cylinder losing spark or no fuel?
Cylinder 4 plug cap should not be sparking like that. Bad plug lead? If it is no 4 on its own then more likely to be plug lead than coil. Swap no 1 and 4 leads on the front coil and see if problem moves from no 4 to no 1.
What plugs have you? Have they bobbins on them?

I did this. I swaped no 1 and 4 plug leads in between eachother and the problem still persists at cylinder 4.

As plugs i have NGK D7EA. I'm not sure what you mean by "bobbins on them"?

Also regarding “Cylinder 4 plug cap should not be sparking like that.” : all the plug caps are sparking exactly like that. If i am taking each one of them out with the pliers (while the engine is running),  and i touch the metal part of the pliers, or the metal housing of the plug cap, the spark strikes me quite hard, no matter the cylinder or the number of the plug lead

Hi Katsawa,

I'm thinking you have two problems (or more) a blocked filter, and a problem at cylinder four.

When it won't start, check if spark plug four is wet or dry. 

After replacing the filter, a few quick checks at cylinder four. With a screwdriver between injector one and your ear, you should hear a clicking as it opens and closes. Should be the same for two, three, and especially four. 

There is a vacuum hose at cylinder four throttle body, it might be leaking or unplugged, it should also be dry. Check it out. 

That it revs better with the start button pressed, makes me wonder if the temperature sensor is dirty or not working properly. It's near the radiator, behind, near the bottom. Unplugging it might give similar symptoms, or cleaning it might fix it. 

I agree, no changes when removing cylinder four spark plug lead shows it's basically running on three cylinders. When you removed cylinder two lead and it stalled, that's probably because it would then be running on not much more than two cylinders (one and three)

daveyson wrote:Hi Katsawa,

I'm thinking you have two problems (or more) a blocked filter, and a problem at cylinder four.

When it won't start, check if spark plug four is wet or dry. 

After replacing the filter, a few quick checks at cylinder four. With a screwdriver between injector one and your ear, you should hear a clicking as it opens and closes. Should be the same for two, three, and especially four. 

There is a vacuum hose at cylinder four throttle body, it might be leaking or unplugged, it should also be dry. Check it out. 

That it revs better with the start button pressed, makes me wonder if the temperature sensor is dirty or not working properly. It's near the radiator, behind, near the bottom. Unplugging it might give similar symptoms, or cleaning it might fix it. 

I agree, no changes when removing cylinder four spark plug lead shows it's basically running on three cylinders. When you removed cylinder two lead and it stalled, that's probably because it would then be running on not much more than two cylinders (one and three)

Hi, thanks for the detailed information.

"When it won't start, check if spark plug four is wet or dry." - i checked the spark plug when it tried to start and it is like dark wet, but i don't think that's oily, I think it is unburned gas..

I already ordered a new fuel filter, and I will check for the clicking on the injectors after i replace it.


Regarding the vacuum hose, I don't think it is unplugged and from what i remember, it was not very wet, but some gas/oil (i'm not sure, it was like a dark color liquid with something in it) was present in that hose, but not in big quantities..
I also tried to remove the vacuum hose when the engine is running, and also to put a finger on the plug of the hose on the intake plug. When i removed it completely the engine stopped right away and when i covered the plug with my finger, it was running exactly the same as with the hose on

Regarding the start button, I will try and find the temperature sensor and will check it's condition.


Thank you!

The vacuum hose should be absolutely dry inside. Any moisture would probably smell of fuel, and is a sign that the fuel pressure regulator diaphragm is leaking, then the regulator needs to be replaced.

Maybe this is causing over fueling, rather than the temperature sensor.

The fuel pressure regulator is difficult to get to, the bottom air filter box wants to be removed, then it's also possible for a closer look at the vacuum hose.

On the question of the spark plugs. NGK D7EA are ok, 

The bobbins are screwed on to the top of the plug. The top of the plug is threaded. If you have the threaded tops showing then the bobbins are missing. These dont come with the plugs but are easy enough to get. If you run without them you destroy the inside of the plug cap. I no longer have original plug caps on any of my Ks, they all break down eventually.

I did not think of the fuel pressure regulator diapragm, so if it fails then fuel can come into the vacuum hose and cause extra rich running in no 4.

Also have a look at the plug for the fuel injector on that cylinder they are not the most robust design and corrosion can cause issues here, pull the connector plug and look into it if there's green copper corrosion try give a rub of a fine "swiss" file to clean up contacts (gently)
Regards
Bill

Take out the injector and clean its filter and check to see it is working properly.

Hi Katsawa,
I watched your video that shows your problems with your K100. You did not mention whether you checked the exhaust valves on this bike. I had similar symptoms with aK75 that had very tight exhaust valves. Remember, the exhaust valves on these bikes tend to get tighter. Once I checked and replaced the shims to create the proper gaps the bike now runs perfectly. Good luck!

Did you have the bobbins fitted on the spark plugs as Olaf asked earlier? Can't see it on the video clearly, but looks not. Cheers, Rene