I have a 1987 K100LT. Sat for last 5 years. Retired since then and have been trying to get on the road again. Accomplished some component R&R. New Fuel injectors, new battery. Troubleshooting so far. Rebuilt starter, engine turns over. Then all of sudden no electrical power.  Main issue is when battery is connected horn relay engages. No indication on any indicators; gear position, neutral indicator, lights, etc. Engine will not turn over. Engine ignition sw and starter/kill sw function correctly with VOM. I isolated the horn sw by disconnecting the connector below fuel tank. Horn relay still has power. I’m using the electrical diagram from the Haynes manual. I’m not a very good electrician so difficult for me troubleshoot. I need some help.

When you say the horn has power, do you mean that the horn relay coil (pin 85 / 86) have power or that the horn relay contacts 30 / 87 have power?  The horn relay pins 30 and 86 are common and connect to Green/Red wire that comes from fuse 7 which is fed by the Load Shed Relay.  LSR coil gets fed power from the kill switch and grounds through the starter motor.  Maybe the LSR is bad or maybe the starter motor is not overhauled properly.  Did these symptoms all of a sudden appear?  Or are they a result of the bike not being used very much and developing problems?  If the latter, then maybe go through all the ground connections and clean/tighten them to make sure ground circuits are good.  This is especially true for the starter motor because it is part of the grounding circuitry.

robmack wrote:When you say the horn has power, do you mean that the horn relay coil (pin 85 / 86) have power or that the horn relay contacts 30 / 87 have power?  The horn relay pins 30 and 86 are common and connect to Green/Red wire that comes from fuse 7 which is fed by the Load Shed Relay.  LSR coil gets fed power from the kill switch and grounds through the starter motor.  Maybe the LSR is bad or maybe the starter motor is not overhauled properly.  Did these symptoms all of a sudden appear?  Or are they a result of the bike not being used very much and developing problems?  If the latter, then maybe go through all the ground connections and clean/tighten them to make sure ground circuits are good.  This is especially true for the starter motor because it is part of the grounding circuitry.

12.7 v at pin 85. I rebuilt the starter and engine would crank normal. When the electrical problem started I pulled the starter and tore it down. I didn’t  notice anything wrong. Cleaned the battery cables ground on the engine case. Cleaned the brown wire grounds under fuel tank.

So when you measure 12.7V at pin 85 (Brown/Yellow) is the ignition switch set to on or off?  If the ignition switch is off and you read that voltage, then there is a problem with the LSR.  Try swapping the LSR with the horn relay.  If, on the other hand, the ignition switch is on and you do nothing else except read the voltage on pin 85 of the horn relay, then that is normal.

When the starter won't turn over, is the neutral light on?  If not, have you tried pulling in the clutch handle when starting?

robmack wrote:So when you measure 12.7V at pin 85 (Brown/Yellow) is the ignition switch set to on or off?  If the ignition switch is off and you read that voltage, then there is a problem with the LSR.  Try swapping the LSR with the horn relay.  If, on the other hand, the ignition switch is on and you do nothing else except read the voltage on pin 85 of the horn relay, then that is normal.

Thnx. I’ll try tomorrow. I appreciate the help.

Another check, some drawings have the load shed relay labelled as the horn relay, check the colours of the wires to the relay that engages when the battery is connected, to verify it's the horn relay. With the horn switch reconnected check if the horn works with the horn button pressed.

How's fuse 1? How's the other fuses for that matter? If fuse 1 is bad you wouldn't have lights at the instrument cluster, but then there would still be some function with the indicators, then check that there is power to fuse one. The flasher unit also gets power from fuse 3. The clock also gets power from fuse 3, so if the clock works, fuse 3 is good and receiving power.

daveyson wrote:Another check, some drawings have the load shed relay labelled as the horn relay, check the colours of the wires to the relay that engages when the battery is connected, to verify it's the horn relay. With the horn switch reconnected check if the horn works with the horn button pressed.

How's fuse 1? How's the other fuses for that matter? If fuse 1 is bad you wouldn't have lights at the instrument cluster, but then there would still be some function with the indicators, then check that there is power to fuse one. The flasher unit also gets power from fuse 3. The clock also gets power from fuse 3, so if the clock works, fuse 3 is good and receiving power.

Thnx for the info. I checked wiring diagram by wire colors. The illustration I am using is incorrect for three relays. What I thought was horn relay is really load shedding relay. I will continue troubleshooting.

OK1987LT wrote:

robmack wrote:So when you measure 12.7V at pin 85 (Brown/Yellow) is the ignition switch set to on or off?  If the ignition switch is off and you read that voltage, then there is a problem with the LSR.  Try swapping the LSR with the horn relay.  If, on the other hand, the ignition switch is on and you do nothing else except read the voltage on pin 85 of the horn relay, then that is normal.

Thnx. I’ll try tomorrow. I appreciate the help.

Daveyson said check wiring diagram by wire color. I did. What I thought was horn relay is load shedding relay. So LSR pin 85 has voltage when battery is connected.

I found the easiest way to check the wiring was to have the diagram blown up and laminated. You can then trace the circuits a lot easier and mark them off with Chino graphic pencils which are available in different colours. The Chino Graphic pencil can be removed easily with wax and grease remover. I also have a smaller laminated one that I can carry on the bike
Regards Martin.

1987 K100LT no electrical power except at load shed relay. No start, no lights, no instrument panel. I have posted this before back in June. Diagram I used said horn relay. After guidance on this site I checked wiring diagram and verified it is the load shed relay. Swapped LSR with horn relay. Verified continuous 12+ volts at LSR socket (should not have voltage, relay engaged). I had rebuilt the starter. I disassembled the starter several times to verify correct assembly. No issues. Bought used serviceable starter online. Replaced starter relay. Disassembled ground wires under tank, cleaned, sanded frame at connection. Cleaned main ground wire from battery to case. I am not that good at troubleshooting electrical problems. I’ve read kill switch only affects the engine running not lights. I’m thinking ignition switch. Any help appreciated.

Is you clock live or showing display?

92KK 84WW Olaf wrote:Is you clock live or showing display?

No. No displays.

With a jumper wire from battery positive to fuse three, does the clock come on?

How many red wires are connected to battery positive?

No power at all is strange, has me wondering about the battery and if you have a break in the earth wire. Its not uncommon.

OK1987LT wrote:Verified continuous 12+ volts at LSR socket (should not have voltage, relay engaged).

Which pin? 

LSR Pin 87 (the front pin) connects to the battery (unfused) and should always be at 12V, even when the bike is turned off.

Yes, sounds like a ground problem to me too.  In any event, first thing to check with general electrical system problems is the ground connections.  In my experience that is the main source of that kind of problem.

OK1987LT wrote:I’ve read kill switch only affects the engine running not lights. I’m thinking ignition switch. Any help appreciated.

The kill switch only cuts power to the brake light. (To the brakes switches actually.)

It also cuts power to:
Ignition coils
Clutch switch
Instrument Cluster
BMU
Heated grips

OK1987LT wrote:I’m thinking ignition switch.

So am I. I'm also thinking of a number between 5 and 9.

When my Brick's ignition switch failed, I was cruising at 70mph through a narrow valley on two-lane pavement instead of on the Cross Bronx Expressway at rush hour so luck was obviously on my side. The instrument cluster shut down, lights shut off, the engine stalled and the starter wouldn't operate. I already knew what the symptoms' source was from all the bedtime stories in the K-100 forum and Motobrick, so I used magical thinking to get the Brick started. I wiggled the key back and forth within the lock cylinder then turned it to On and tried starting a half a dozen times. At last it started, idled and revved with no hesitation and all appropriate bulbs lit.

Buoyed by success, I needed to convince myself again that the switch was the problem so I shut down the engine and did the wiggling routine again. After several vigorous wiggles-to-On, it started again, so I shut it down again, tempting fate. One more time, and after several tries—"several then being defined as more than five but less than nine—it started and ran the last 15 miles with only one hiccup. Cleaning the switch body, polishing the contacts and lubing the works has kept it operating for the last three years.

Give it some wiggles—some being defined as three attempts comprised of eight or less wiggles-to-On. Clean it regardless of the outcome.    Initiate magical thinking. At least you won't be spending any money.

Maybe also check for power at the fuses which should have constant power.

When you turn the key on, you should hear a faint click from relay box, that should be the load shed relay clicking. If it clicks that means the ignition switch is getting power and sending it to the load shed relay.

Better yet, turn the key on and check for 12V at the green wire on the back of the ignition switch.

The red wire is 12V in. The on position of the ignition switch should close the circuit between that and the green wire.

But if the clock isn't on with the #3 fuse inserted then something else may be wrong.

Is it possible there is an issue with the new relays fitted? 

That said, the clock should stay live at all times but its out too. 

Could an instrument cluster fault create this issue?

I had a weird fault on my K100RS not long after I got it and its coming back to me now that the effect was something similar. The indicator relay. As I had spares and a few Ks I just pulled one from another one and it sorted it.

daveyson wrote:With a jumper wire from battery positive to fuse three, does the clock come on?

How many red wires are connected to battery positive?

When I first looked only two black wires. Checked wiring diagram and saw RED wires at the starter. Embarrassed to say I had swapped positive lead and starter lead!! Instrument cluster works. Thanks for opening my eyes. 

Before I figured out the swapped wires I jumped positive terminal to #3fuse. Starter engaged! Another clue for my error. 

Thanks again for everybody’s help. My troubleshooting is improving.

Merged duplicate posts on same subject/same section for easier follow-up, and to allow future readers to see the remedy, if worked out.

OK1987LT wrote:When I first looked only two black wires. Checked wiring diagram and saw RED wires at the starter. Embarrassed to say I had swapped positive lead and starter lead!! Instrument cluster works.

Ah well. I've done it at least twice...