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Discussion Starter #1
Hi all, I'm new to the forum, hopefully I'm posting in the right place.

A few months back a friend gave me his old rotting (sat for 15 years) K75S and I'm slowly putting it together. I've replaced the clutch, new fluids everywhere, had to get a new tank w/ all new internals, serviced the injectors, lots of new plastic and hoses etc. etc. etc.

This past weekend I was super excited thinking that I would be able to fire it up for the first time. It still needs some things (brake lines, tires), but I thought it would run. It didn't.

It's having the same problem that the PO had prior to putting it away. It has a new battery and I've gone through and patched up a few chewed wires and bad connectors. When I go to start the bike I see no gear indicator or neutral light on the dash (despite being in neutral). The GPI switch is new and tests okay. I have two instrument panels that give me the same result so I'm guessing its not the GPI board either. So, it's probably in the wiring harness.

The clutch bypass doesn't work either. The clutch switch tests okay.

The fuel pump doesn't come on and there is no starter noise (click or otherwise). I'm a real electrical noob, testing the switches as noted is probably the most advanced electrical work I've done.

What's next for me? Please pretend that I'm 10 years old when explaining electrical testing procedures to me. I have a multi-meter but I barely know how to use it.

Anyone care to help me troubleshoot? Thanks in advance!

Dan
 

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das27417 said:
Hi all, I'm new to the forum, hopefully I'm posting in the right place.

A few months back a friend gave me his old rotting (sat for 15 years) K75S and I'm slowly putting it together. I've replaced the clutch, new fluids everywhere, had to get a new tank w/ all new internals, serviced the injectors, lots of new plastic and hoses etc. etc. etc.

This past weekend I was super excited thinking that I would be able to fire it up for the first time. It still needs some things (brake lines, tires), but I thought it would run. It didn't.

It's having the same problem that the PO had prior to putting it away. It has a new battery and I've gone through and patched up a few chewed wires and bad connectors. When I go to start the bike I see no gear indicator or neutral light on the dash (despite being in neutral). The GPI switch is new and tests okay. I have two instrument panels that give me the same result so I'm guessing its not the GPI board either. So, it's probably in the wiring harness.

The clutch bypass doesn't work either. The clutch switch tests okay.

The fuel pump doesn't come on and there is no starter noise (click or otherwise). I'm a real electrical noob, testing the switches as noted is probably the most advanced electrical work I've done.

What's next for me? Please pretend that I'm 10 years old when explaining electrical testing procedures to me. I have a multi-meter but I barely know how to use it.

Anyone care to help me troubleshoot? Thanks in advance!

Dan
While most of the traffic is geared to the newer K-bikes there are still some of us with bricks who monitor the site regularly.

You've mentioned a number of checks but have you done some of the basics?
- Have you checked fuses?
- Does the headlight come on with the key?
- Any power to the key switch?
- Any other lights on the instrument cluster?
- Do any of the relays click when the key is turned?
- Do you have a wiring diagram?
 

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Discussion Starter #6
Thanks for the response Nick, I'll post on the other forum but I appreciate the help here too. Here's what I've got in response to your questions. As I mentioned I'm a real noob with electrical (pretty good mechanically).

You've mentioned a number of checks but have you done some of the basics?
- Have you checked fuses? All fuses are brand new and working.
- Does the headlight come on with the key? Yes the headlight has full functionality as do the indicators, horn and aftermarket lights the PO had installed.
- Any power to the key switch? The key does work.
- Any other lights on the instrument cluster? The instrument cluster does light up. I'm not real familiar with the bike so I don't know if anything else is missing but it lights up, the clock works.
- Do any of the relays click when the key is turned? I can hear a click in the relay box, I'm guessing its the load shed relay but that's a wild ass guess.
- Do you have a wiring diagram? I have it but I don't know too much about what to do with it. What I really need is a class in electronics.

What's next? Any advice is greatly appreciated and don't worry about being too descriptive, I'm really not good with this stuff (yet). Thanks!
 

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das27417 said:
Thanks for the response Nick, I'll post on the other forum but I appreciate the help here too. Here's what I've got in response to your questions. As I mentioned I'm a real noob with electrical (pretty good mechanically).

- Any other lights on the instrument cluster? The instrument cluster does light up. I'm not real familiar with the bike so I don't know if anything else is missing but it lights up, the clock works.
- Do any of the relays click when the key is turned? I can hear a click in the relay box, I'm guessing its the load shed relay but that's a wild ass guess.

What's next? Any advice is greatly appreciated and don't worry about being too descriptive, I'm really not good with this stuff (yet). Thanks!
My 1993 K75S w/ABS has the following instrument lamps when the key is turned to on:
- ABS lamp flashes
- oil light is on
- battery light is on
- center warning lamp is on (brake light test)
- head and tail lamp are on
-- the center warning lamp does not go out until the brake lamp illuminates from both the foot and hand brake - ABS must also be fault-free

- any change when the starter button is depressed? A relay click, lamps go dim?
Is the engine stop switch in the run position? Does it matter if the clutch is pulled in releasing the interlock?

Be sure to post any updates and a solution if found.
 

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re: 1991 K75S electrical help

I believe you may have diagnosed your own problem... You say the green neutral light does not come on even though the bike is in neutral. If the bike is not in neutral, the starter will not work. This is the symptom you are having. The bike senses this through the gear indicator switch in the back of the transmission. not sure if just unplugging that switch would allow the starter to work or not - depends if it is sensing an open or closed circuit for the interlock but good design would be to require a closed circuit to allow the bike to start. Of course the neutral bulb may just have gone but the symptoms fit what i am describing. You can test the operation of the switch by measuring resistance across the pins in the connector as you operate the dear shift.

Bob
92 K75RT
 

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Discussion Starter #10
Sorry its been a while since I've been able to log in. I have not been able to fix the problem yet. I took the wiring harness off, rewrapped it while checking for any shorts or other potential issues. I didn't see any problems and after reassembly the problem remains. I'll try to answer some of the helpful questions asked and please chime back in! I really appreciate the help!

My 1993 K75S w/ABS has the following instrument lamps when the key is turned to on:
- ABS lamp flashes I don't have ABS
- oil light is on It is on
- battery light is on It is on
- center warning lamp is on (brake light test) It is on
- head and tail lamp are on They are on
-- the center warning lamp does not go out until the brake lamp illuminates from both the foot and hand brake - ABS must also be fault-free I think I'm okay here.

- any change when the starter button is depressed? A relay click, lamps go dim?
Is the engine stop switch in the run position? Does it matter if the clutch is pulled in releasing the interlock? No changes happen when the starter button is pressed. I did take it apart and clean it, looks okay. The switch is in run position. There is no change when the clutch is pulled or if its in neutral or not.

What next?
 

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Discussion Starter #11
rjfish50 said:
I believe you may have diagnosed your own problem... You say the green neutral light does not come on even though the bike is in neutral. If the bike is not in neutral, the starter will not work. This is the symptom you are having. The bike senses this through the gear indicator switch in the back of the transmission. not sure if just unplugging that switch would allow the starter to work or not - depends if it is sensing an open or closed circuit for the interlock but good design would be to require a closed circuit to allow the bike to start. Of course the neutral bulb may just have gone but the symptoms fit what i am describing. You can test the operation of the switch by measuring resistance across the pins in the connector as you operate the dear shift.

Bob
92 K75RT
Thanks Bob! I have tested both the GPI and clutch switches and they both check out okay. So the problem is somewhere else, in the harness or I don't know. I took the harness apart and retapped it and it looked okay... I also have two instrument clusters and both give the same result so I think its not the card in the cluster. What next??? Thanks for all your help!
 

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Have you removed and cleaned the negative battery lead at the battery and the trans housing? Have you disconnected the connector at the control module under the seat and cleaned the contacts? Have you removed the five ground wire connectors and cleaned them , they are bolted to the main frame on the left side of the center tube just aft of the ignition control module? Sidestand switch, checked? Try , putting the gearbox in neutral , turn key on , pull clutch lever in and press starter button. Anything happen? Be sure that you disconnect the battery, neg first and then pos BEFORE you disconnect any control module connectors on this bike. You may be dealing with a damaged control module. Craig
 

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Remove and bench test the starter and fuel injection relays. Bosch relays have pins 85, 86, 87 and 30. One pair of contacts activate a solenoid which connects the other two contacts.

All terminals numbered 30, IIRC are connected to battery positive, and the female side of the socket the relay fits in should have power at that point all times. Check that this is so for both relays named. The starter relay is the rectangular one at right side middle of the relay box (in my '85 K100RS anyway) and the fuel injection relay is square at left front.

You should grok the function of relays and how to test them, though the seldom go bad, they can malfunction.

Next remove the starter and certify the brushes are okay (even length, not too short) and clean all the black dust out of the case, then reassemble and test.

Crazy Frog (Berndt Vogel) authored a useful troubleshooting guide.which may be of use, try find and go through it.
 
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