Just stops running

[Jethroww]

Hi. I bought 1988 K75S in April 2017. 76500 km on engine. Ran fine for 1 minute then loud banging from engine.
Found a used black engine 1990? with I think was told 110,000 km on it. Installed the engine and ran fine until
last year.  While driving it would just stop running.  No misfire no fuel problems  just completely stop for a
second or 2 and then just start running again like nothing had happened.  This happened a few times last
year. Then in September it just completed stopped  running at around 80 km per hour.  Trying to jump star while
I was slowing down nothing. Trying to start nothing.  Rolled to stop and started to check fuses etc. Thought it
might be fuel pump because I didn't hear it running.  After about 40 min of checking  and not finding anything
I tried to start the bike again.  After the second attempt I heard the pump running after I let go of the start button.
2 more tries and it started up. Drove home with no problems about 25 Kilometers. Did some research and
thought it might be the Hall sensor.  Started the bike up and let it idle for about 30 min. The second time it
just stopped and would not start back up. Tried starting it a few more times different days and it wouldn't start.

Last October ordered a new Hall sensor  from Euro Motoelectrics.  Replaced it this April.  Started up after a few tries.
Starting using the bike as my daily driver in May. Then May 12 after work 4pm tried starting and gas just dripping of
exhaust pipe. Checked over bike no problems found.  Pulled #7 fuse and bike started up but died. Put all riding gear
back on and got the bike running with fuse back in. Kept the rpm around 3,000 and started my ride home about 84 Kilometers.  Stalled 1st time for a second  and then started back up. 2nd time was about 10 Kilometers later and
took about 4 attempts at starting to get it running.  With keeping 3,000 rpm at stop lights made it home in about
90 minutes.  Bike idled fine. Started back up ok. After research cleaned the coolant temp sensor wire connection
and ignition switch with Deoxit 5.
Drove it for about 45 min with no problems stopping and starting back up. Thought I fixed the problem.  Monday
morning on my way to work about 17 Kilometers from my place the bike just completely stopped again. Same
thing as happened last September.  Waited about 15 min tried starting and 3rd attempt it started back up. Drove
back home with no problems.  Have put about 800 Kilometers on this Hall sensor.  I have new plugs and wires
NKG (DR7EA). I don't think they are the problem.  The bike now has 134,000 Kilometers on it. So I have put
about 56,000 Kilometers on this engine.  Any help in what could be causing this problem is greatly appreciated.
Thanks Jethroww

[know_fear]

Electrical issues of a spurious nature like that can be very difficult to solve.
The first bit of advice to come from the regulars of this forum will be to unplug and clean all the connectors
giving special attention to the ground point on the frame under the tank.
You actually want to have a permanent "no start" situation in your garage so you can identify the source.
rbm will hopefully chime in. He's the best electrical guru and is also somewhere in Ontario.
Good luck.

[The Mighty Gryphon]

You may have multiple problems.  First thing that came to mind as I read your tale of woe was, "have you cleaned the ignition switch?" 

If you do a search here you will find a write up on how to do it.

[Laitch]

Hi. I bought 1988 K75S in April 2017. 76500 km on engine. Ran fine for 1 minute then loud banging from engine. Found a used black engine 1990? with I think was told 110,000 km on it..  . .   The bike now has 134,000 Kilometers on it. So I have putabout 56,000 Kilometers on this engine.

I can't understand how you arrived at the final total kilometers using the figures that preceded it. Did you leave off telling us the mileage of the bike when you swapped in the replacement engine? Nevertheless, have you replaced the fuel filter? When it quit the first time and came completely to a stop, did the dash lights shut off? When the bike wouldn't jump start or start up, do mean you could crank it and it wouldn't fire, or it had no electrical power at all?

Here's instruction concerning Gryphon's observation. If the dash lights shut down when the power shut down, the ignition switch is a likely suspect.

[Jethroww]

Hi, first about the Kilometers on this engine. I now have 134,000 - 76,500 = 57,500. The engine had about 110,000 on
it when I put it in. Now this engine has about 167,500 Kilometers  on it.

With the flooding problem I did
"After research cleaned the coolant temp sensor wire connection
and ignition switch with Deoxit 5. "
Hope this is fixed now.

I will remove the tank and check the frame ground.  When I put the engine  5 years ago I cleaned the connection
and put some dielectric grease on it.

I will put a new fuel filter in. I will also replace the spark plugs/wires.
Will also look for any electrical problems at the same time.
Thanks  Jethroww

[Laitch]

Hi, first about the Kilometers on this engine. I now have 134,000 - 76,500 = 57,500. The engine had about 110,000 on
it when I put it in.

Thanks for the clarification. I see you were equating "bike" with "engine" and I wasn't.

Could you answer my question concerning the dash lights and stalling?

[Jethroww]

Hi, sorry had reply back and preview lost that whole reply.

Must a mist it 😁 in 2nd attempt.

Yes everything else works. Lights stay on and I can crank
engine but no start. No sputtering missing.  Just 1 second
running fine then dead.  Have replaced the Hall sensor this
April with a ECE I bought last October after that episode with
the same cutting out as now. Could that have broken with
only about 800 Kilometers and 2 weeks of use?
Thanks Jethroww

[frankenduck]

Put your ear to the left side of the tank. When you hit the start button you should hear the fuel pump whir. (It only runs when the engine is turning.)

If you don't hear the fuel pump whirring then it's most likely the fuel tank connector.

[Jethroww]

Hi, will listen and Deoxit the connection when I take the tank off to check the ground.
Ok that explains why I only heard the pump after I let go of start button.
Thanks Jethroww

[frankenduck]

The fuel pump connector usually fails internally. Deoxit won't hurt anything though.

[Jethroww]

Hi, cleaned the frame ground.

20220605_131457.jpg (62.05 kB . 768x576 - viewed 674 times)
Cleaned the tank/pump connector and found the top left
connector was a bit brown looking.
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Replaced the spark plugs and wires. The plugs had 0.038 to 0.040 gap.
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Old wires.
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Picture of pump. Used a screw driver to see if I could move
the connected wires. No movement at all. Will change filter
when tank is almost empty.
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Cleaned the battery connections and ground to transmission.
Bike started and ran ok as I worked through these repairs.
To see that I didn't cause any other problems along the way.
Will have to go on a long ride hopefully this week.
Thanks Jethroww

[Laitch]

Will change filter when tank is almost empty.

Why wait? Use one of these to empty the tank fuel into a fuel can temporarily any time you want to get in there.
Your fuel pump's position is hanging low in the vibration damper; it should be similar in position to the one in the photo below if its an OEM pump. Verify that it is not loose. I encountered one that was bottoming out on the floor of the tank, its filter basket was damaged and the mess was causing fuel intake restriction. View what you've got in there.

[frankenduck]

If you suspect that it is the fuel tank connector then you can bypass the connector and run power directly to the fuel pump with some extra wire and a couple of ring terminals. (The smaller terminal is 12V, the larger is ground.)  Then use some Posi-Taps to tap into the green/white (12v) and brown (ground) wires on the other side of the connector.

[Jethroww]

Hi Laitch, I will pick 1 up this week and empty th tank.
I have only changed the filter a few years ago.
The pump I have never touched.  Will pull it and
see how it looks and change the mount if possible.
frankenduck thanks for that info will try if the pump stops.
Thanks Jethroww

[Jethroww]

Hi, changed the fuel filter another Carquest #86032 . Pulled the pump and everything
was tight.  Noticed the pump filter was not seating properly on the vibration damper.
Removed the pump and installed the screen properly.  Matched the 2 pump  groves
with the 2 in the damper. Was on a slight angle before. The pump screen has a smash
rip on the part that sits against the pump. The damper felt a bit rubbery/soft. Is that normal?
Should it be replaced? What would be a good place to get the parts? 
Euro Motoelectrics, beemerboneyard? Here is a picture of the pump as found in the bike.

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Will take it for a long ride and see if I fixed the problem.  Will order parts after some
suggestions on a good quality part/suppliers.
Thanks Jethroww

[Laitch]

The damper felt a bit rubbery/soft. Is that normal?
Should it be replaced? What would be a good place to get the parts? 
Euro Motoelectrics, beemerboneyard?

Does the yellow arrow point at sludge accumulation inside or outside that filter basket?  Replace it anyway because it looks like hell. If you rub the damper with your fingers will you get black residue on them? Regardless, my inclination from this distance would be to replace both the damper and the filter with Euro Motoelectrics stock. Is the fuel tank interior relatively clean or does it have floaters and a gooey patina on part of its surface?

[Jethroww]

Hi Laitch,  almost all was on the outside.  Just a bit on the inside  I think it was slowly making it's way through the screen.
I don't know what it was. I ran water from a garden watering jug back through the screen and it cleaned up. I've been
driving it for 5 years now and this is the first time I have taken the pump out. The inside of the tank is spotless silver
color. Will order the parts and hopefully continue driving the bike until I get them
Thanks Jethroww

[Jethroww]

Hi, update on my progress.  Rode to work today and 5 stops. About 200
Kilometers wither no problems.  Hope it is fixed. Just some pictures of
fixes.

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I also found this under the tank. Any idea what it's for?

Screenshot_20220610-211256_Gallery.jpg (14.15 kB . 324x576 - viewed 630 times)
Laitch will order 2 sets of the parts. Trying to get a K100 going that has sat
for many years.
Thanks for all the help.
Jethroww

[Jethroww]

Hi. Just opened my fuel filter.  Hear are some pictures.


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As mentioned many times before  "change the fuel filter every year".

Thanks Jethroww

[frankenduck]

You don't need to cut a fuel filter apart to tell how clogged it is.  Just pull it out and try to blow through it in the direction of the arrow. If there's resistance then it should be replaced.

[Jethroww]

Hi, never thought of doing that. Thanks for  that tip frankenduck.

[Jethroww]

Hi, the other reason I cut open the filter was to see what was inside. It looked black. I am wondering
if that is the damper slowly breaking apart.
Just informed by Euro Motoelectrics  that the damper I ordered they don't have in stock
 Laitch as you recommend Euro Motoelectrics and I can't get it from them. Would
beamerboneyard be the next best place to get one?
Thanks Jethroww

[Laitch]

You won't know who has what until you ask them, apparently. Try tills.de here. They're reliable. MaxBMW might have them; they're reliable too. If the damper isn't discoloring your fingers when you rub it, or feels like it has a firm grip on the pump, go riding.     

[know_fear]

I had two damper kits sent to me from Beemer Boneyard last month.

[Laitch]

I had two damper kits sent to me from Beemer Boneyard last month.

Thusly.