1991 K75S electrical help? - K-Bikes.com - Excellence in Motion
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post #1 of 13 (permalink) Old Apr 27th, 2015, 12:07 pm Thread Starter
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1991 K75S electrical help?

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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post #2 of 13 (permalink) Old Apr 27th, 2015, 5:09 pm Thread Starter
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Next step? Anyone? (crickets)
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post #3 of 13 (permalink) Old Apr 27th, 2015, 7:28 pm
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More help for your bike is to be found at motobrick.com
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post #4 of 13 (permalink) Old Apr 27th, 2015, 9:55 pm Thread Starter
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Ok maybe I'll have better luck there.
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post #5 of 13 (permalink) Old May 1st, 2015, 7:37 am
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Quote:
Originally Posted by das27417
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?

Nick
1993 K75S
1991 R100RT
1982 Yamaha XJ650RJ Seca
1978 R100S
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post #6 of 13 (permalink) Old May 1st, 2015, 5:17 pm Thread Starter
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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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post #7 of 13 (permalink) Old May 3rd, 2015, 2:19 pm
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Quote:
Originally Posted by das27417
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.

Nick
1993 K75S
1991 R100RT
1982 Yamaha XJ650RJ Seca
1978 R100S
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post #8 of 13 (permalink) Old May 23rd, 2015, 5:47 pm
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So… any solution or progress?

Nick
1993 K75S
1991 R100RT
1982 Yamaha XJ650RJ Seca
1978 R100S
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post #9 of 13 (permalink) Old May 29th, 2015, 11:53 pm
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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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post #10 of 13 (permalink) Old May 30th, 2015, 1:51 pm Thread Starter
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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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