Just stops running

[Jethroww]

Hi this is the story.
- April 2017 bought 1988 k75s with 76,634 Kilometers. Didn't hear it running.  Bought battery and after starting bike engine made a loud banging noise. 
- replaced engine with I think a 1987? With about 125,000 Kilometers on it.
- ran fine no problems.
- cut out like ignition stoped working a few times over the first 4 years it was my summerdaily driver.
- September 2021 132,223 Kilometerson the bike odometer and the bike just stopped running the started right back up. About 15 minutes later just stopped running. Seemed fuel pump stopped running.  Didn't hear pump running  when I tried to start bike. On shoulder of road looked bike over. Checked fuses, wires I could see battery all see okay. About 45 min later tried starting bike wouldn't run but I heard the pump running after I let go of the starter button.  2 more tries and bike started running.  Drove for about another 35 min home without any problems.  After some research I thought it could be the hall effect sensor.  Started and let the bike idle for about 30 minutes a few days later.  About a week later started the bike up and let it idle again. About 20 minutes later the bike just stopped running.  Tried starting it again with no luck.  Tried starting again a few times different days and it wouldn't run.
- October 2021 bought  Hall effect sensor from Euro Motoelectrics.
- 132,500 April 2022 installed the Hall effect sensor
- 135,345 bike seemed it wasn't getting enough gas. Checked tank and seen  fuel pump damper  was big with  soft/ sticky  rubber  feeling.
- 133,565 June 11 2022  new spark plugs/wires, cleaned ignition switch and coolant temperature connector with Deoxit and small amount of dielectric grease put on connectors.
- 135,993 July 19 2022 new fuel pump damper/screen & new fuel filter
- 137,718 Aug 13 2022 new Spal rad fan( old 1 had melted together  brushes) ,Toyota  red coolant,  cleaned wire connections under seat with Deoxit and small amount of dielectric grease added
- 138,645  Aug 21 2022  cleaned  start/kill switch  with Deoxit 5 and small  amount of dielectric grease added.
- 138,797  Aug 29 2022 just stopped  running  about 1 hour into commute to work. Would  not start . Pushed bike for a while.  Tried startup  again and wouldn't start.  This was about a 1/2 hour  later.  When it got light  outside  I saw a puddle under  the bike. Though  it was gas. So I pulled the #7 fuse and the bike started up.  Made it to work. Turned the fan on for the drive home. About  5 minutes  into drive home the bike died/started right back up in less than a second  as before. Made it home 1 hour drive  without any problems.  I turned the fan off but let the bike idle  to see if the fan was working.  About 3 minutes later the started automatically without the coolant light coming on.  Then I turned the bike off. (Should  have let it run to see if it automatically turned off)
- Aug 31 2022 removed tank. Cleaned  ECU with Deoxit 5 & put a small amount of dielectric grease on.  Cleaned all the connectors again with Deoxit 5 and added small  amount of dielectric grease on pins. Added led diode light to fan positive to see when fan turns on/off. Cleaned battery ground again.
- Sept 02 2022 drove bike for about 55 minutes without any problems.
- 138,969 Sept 07 2022 about 35 minutes into commute just got onto highway  401 and bike died but this time like it was running out of gas. Got onto shoulder and tried giving it more gas and then it started running ok. Back onto highway.  About 15 minutes/20 Kilometers later bike seems as it is running out of gas again.  Shoulder  and the bike starts back up. Turned  around  and took side roads back home. About  30 minutes later bike started to miss fire. About 15 seconds later started running fine.  About  1 minute later started miss firing again. Seemed like it was a different  cylinder each miss fire. The bike would idle but once you turned the throttle it would bog out/start to miss fire.
Called CAA and bike is in the garage now.

[The Mighty Gryphon]

Reading your tale of woe I can't help thinking that except for the misfire, you bike is acting exactly like my K75RT when it wants the ignition switch serviced/cleaned. 

At this stage of the game, my first reaction would be to eliminate the ignition switch.  I would get a good toggle switch and wire it in to replace the ignition switch to eliminate that as a possible source of your problems.  I would hide it under the seat where locking the seat could prevent tampering when the bike is unattended.  Beyond that I have no other suggestions.

[Jethroww]

Hi, what did you do to fix the switch problem? I have clean it once as was recommended. I do have a extra switch.  Thanks for the help The Mighty Cryphon 

[daveson]

If the ignition switch or kill switch were faulty the dash lights wouldn't work, I think your dash lights are working.

Fuel or spark? Spark plugs wet or dry? I think they'll be wet, since sometimes you had fuel dripping out the headers.

Maybe move the test lights to before the coils, or easier a timing gun to check for power to the spark plugs while cranking, when in cranking but no start mode. Or just check if there is spark at the spark plugs.

[Laitch]

What is the make and model number of the spark plugs you are using and the plug wires you are using? Do the plugs have screw shank terminals or terminal nuts?

You haven't listed checking the Z-tube connection from crankcase to airbox for leaks, checking the throttle body connections to the airbox for leaks, checking the rubber caps on the throttle bodies for cracks. If the engine will idle, these parts are checked for leaks by spraying a stream of propane around them and listening for a change in the idle; a change would indicate a leak in the seal and the part probably should be replaced. A visual inspection can find obvious cracks in the rubber.

Faulty coil function could be part of this, as daveson indicates. Consult the troubleshooting guide for instructions and resistance values. Link to the guide is at the bottom of the first post here.

[The Mighty Gryphon]

I just take it apart, polish the contacts with 1000 grit paper, and carefully put it back together.  The last time I had to do it, it really wasn't that bad inside as it had only been 4-5 years since the last time I cleaned it.  As you might have noticed, the contacts in the switch don't seem to have a lot of contact area or pressure to hold them together. 

In my opinion, the factory switch isn't a very good design, and after 30+ years is probably not going to be very reliable going into the future.  Also, it's location at the steering head exposes it to vibration from the engine and front wheel which also can't be good for it.  As I suggested, if you could come up with a way to replace the factory switch with a good toggle switch concealed under the seat it would go a long way to either positively identify the problem and/or correct it. 

You could also try replacing the original switch with your replacement. 

How strong are the vibrations at the handlebars?  You might want to try loosening the screws that hold the switch pad to isolate it from frame shocks and vibration, maybe even detach it completely and let it temporarily rest on some foam to absorb shock. 

[sammysnail]

Jethroww, I have experienced similar symptoms twice. One time the cause was a poor connection in the kill switch. The other time the problem was a poor connection in the ignition switch. This is a trap for young players, as the ignition switch contains TWO switches. Thus if only one of them fails, then when the switch is turned on SOME THINGS WILL WORK and some will not. This caught me out, and yes, I do know what a Hall sensor looks like. In fact I built a new one.
My advice is to check these two (or if you like, three) switches.

[rbm]

Only problem is I can't find the  PosiTaps here in Cambridge Ontario Canada.  Any suggestions on were I could get
some would be appreciated.

. Try Cruchfield:   https://www.crutchfield.ca/S-poMuwoh6Ddb/shopsearch/posi-products.html

[frankenduck]

I always get my Posi-Taps from Ebay.

[The Mighty Gryphon]

If all you are going to do is check the voltage in a wire you don't need the Posi-Taps.  Just sick a pin in the wire and attach an alligator clip to it.  A pin will make a smaller hole in the insulation than the Posi-Tap.

[pobiddy]

Hi Jethroww,
Great and interesting post. It's nice you've been trying all the ideas that this forum have suggested. I did notice that you pulled/replaced fuses and were able to get it running after a while. My K100RS had a few weird electrical gremlins that were all related to the fuse box. In my case, the fuse receptacles were dirty which was causing my issues. Once I cleaned them I had no more issues. It makes sense that a poor electrical connection there would cause more heat, and a worse connection, and then the problems show themselves until the fuse connections cool down. Not sure if you've done this, but I would clean the heck out of those receptacles, as well as the fuses themselves. The spring tension of my fuse holders seems very weak, but keeping them clean seems to work well enough. Best of luck!

[Jethroww]

Update
Latest changes
139,006  July 14 2023.  Changed temp sensor
   As suggested by rbm and other members changed  the starter brushes
Here are pics of old and new

20230613_110227.jpg (87.04 kB . 768x576 - viewed 170 times)

20230426_111855.jpg (79.26 kB . 768x576 - viewed 181 times)
141,749 Aug 06 2023 back to daily driver
Thanks everyone for all the help and hope this might help others.