K75s wont start-electric questions

[Jbuffalo]

1987 K75s just brought it home yesterday.  Put in spare battery.  Front light work, turn signals work, dash lights work.  Rear tail light does not have power.  Bike will not turn over, no click.  The battery is smaller and old but charged up.  Checked fuses on the left side of bike all good.  What else should I look at?  The owner drove until 3-4 years ago-it all worked then.   thanks Jim

[johnny]

greetings jbuffalo... strap in... you on the resurrection roller coaster... 4 year neglected motobricks generally needs lotts o attention...

you gotts it on a battery tender... on the center stand... kickstand up... fresh gasoline... and a volt meter...

whats your volts on the battery in the moto off the charger...

this is k100 specific... the k75 is different... butts kinda the same...

j o

[Jbuffalo]

The battery is reading 12.45, low, what do it need need?    thanks Jim

[johnny]

greetings...

12.4 volts... rodger that... so... 1st things 1st...

so... its on the center stand... kickstand up... in neutral... key in the run position... kill switch in the run position... when you hit the start button you do not hear anything and nothing happens... butts all the lights are on except the tail light... including the speedo tach dash lights are on as well... is that right...

if thats right the 1st thing i would do is unplug the computer connector... make sure the computer side and the connector side are clean and reseat it and try it again...


j o

[Jbuffalo]

Johnny:  Side stand is up.  Kill switch is on.   Speedometer and tach  light do not work.  Warning, oil, battery, choke, head light, turn signals do.  It does not click or make any noise when the starter is pressed or dimming of dash lights.    I cleaned that electrical connection you mentioned -no change but it was full of brown grease.  I will clean it again tomorrow and use the proper grease.  There is power to the rear tail light and brake light but I have to clean up the wiring. I put in a larger ground wire to the battery and checked the ground on the starter relay- it is grounded.    thanks Jim

[Scott_]

Couple of things to clarify,
the K75's don't have a side stand switch, so no issue with the stand if it is up or not.
The fuel pump won't prime or energize until the starter button is pressed and/or motor is turning/running.

There are 2 safety circuits that can provide power to the starter button for energizing the starter relay circuit. This is in the Vogel diagnostics:
1, the neutral light on the dash has to be lit(so the transmission gear indicator switch has to work),,,, or the clutch has to be pulled in(clutch switch has to close the circuit) in order to get power to the start/kill switch.

[johnny]

rodger all that scott_...

yawl... neutral light on or clutch pulled in or both...

so jbuffalo... with the neutral light on and the clutch pulled in... on the center stand... kickstand up... in neutral... key in the run position... kill switch in the run position... when you hit the start button you still do not hear anything and nothing happens... is that right...

j o

[Jbuffalo]

Correct-Jim

[Inge K.]

From the symptoms so far it seems most likely that you got a problem in the RHS switch assy, or it's connector.

Start with checking if power is present at the connector, which you find under the tank at the right side.
Keep it connected to the harness and measure on both sides of the connector (harness, switch).

With ignition on and when the starter button is pushed, measure if you got power:
In: black/green wire.
Out: black/yellow wire.


The tail and instrument backlight is also powered via the RHS switch assy:
In: green/blue wire.....(you have power at this wire, same wire feeds the headlight).
Out: gray/blue wire.

On US models which have lights always on, these two wires (and the headlight, yellow/white)
should normaly be bridged close to the connector.

[Jbuffalo]

It will take a few days to test this(work calls) thanks to all for your time.  Jim

[Jbuffalo]

Not much time to work on the bike.   The only power at the right switch was to the kill switch and turn signal.  The junction under the tank had power to 2 green wires fused together and one blue.  They were all cleaned up. thanks -Jim

[Jbuffalo]

Only a little time working on the bike.  I did find the wires that go to the ignition were shorting on and off at the connection under the tank.  I am going to put in a new connection.  Jim

[Jbuffalo]

Update on the Bmw K75s.  The starter now turns over.  I cannot say what was fixed as I cleaned many connections and all the grounds and have a new battery.    I have not started the bike as the tank needs cleaning and I am going to change the fuel filter, the hoses look good. I am also removing extra wiring and deer whistles, hey, it never hit a deer.    More question to come.  I have one heated grip to fix. thanks Jim   

[grant71]

hello. please tell me what is a deer whistle.

[Scott_]

hello. please tell me what is a deer whistle.

Something like this.

Supposed to scare deer away to avoid accident.....

[Jbuffalo]

It is plastic and sits on the front of the bike, about the size of a finger.    On this K75s two were on the fairing under the headlight. When the wind hits them they are, according to the sales pitch, giving off a high pitch noise that keeps deer away from the bike.   The have been sold for many years and you can find them on many older bikes especially touring machines.  No electric, no wires.  They have a following. 

[WayneDW]

And, BTW, i had a deer whistle on my Silverwing fairing when I hit a deer.  Seemed to call that sucker right over to me!