2012 - grabbed a 1987 K75 with the intent on stripping it for a parts bike.

I sold almost everything off the bike that I didn't want.  The huge instrument cluster, hard cases, handlebars, everything.
Well, now I can't fire the bike up because (as I learned here on the forum) there are required connections missing.

I joined because this seems to be the BEST K bike enthusiast site in the world.  And I hope I can learn as much as I can from many of you. 




Things I have no clue about:

1) I've chopped the rear of the frame.  After reading Rafael's thread - I wonder do I need to weld a bar to close the frame off back there? I didn't even think of that before I chopped and I am really embarrassed to show how much I have chopped off.  Pretty much chopped right up to the shock mount...

2) If we can move past #1 and I am still worthy, what is the fattest tire one can fit on the front and back of a K75?
I want to go with the same size front and rear if possible, like the Japanese Cafes.

3) With virtually all lights, gauges, speedo etc., removed - I cannot test fire this bike.  I bench tested the starter relay and it works well.  I have a brand new battery pushing 13.4V.  I ran 12V to the starter directly and the motor turned.
But with the key in the ignition all I get is a relay CLICK. Then nothing - the kill switch/starter button don't do a thing.
The turn signal switches produce a buzz from the relay.  (That I can see - with no actual bulbs there)

4) This bike had an alarm system on it.  I tossed most of it out.  The weirdest thing? Above the coils, there is that power outlet.  Above that, on the relay box, is a keyhole.  I have never seen this on any K bike online, anywhere.  I have the key for this but the stupid thing only turns half way, and you can't pull the key back out.
Backside of this key cylinder is connected to a lot of wires which I cut when removing the alarm system.  Methinks I cut something required here...


PICTURES ARE COMING I promise.  I've got a bunch but I need to host them and get URLs.

thanks,
Steve

escodsm wrote:2) If we can move past #1 and I am still worthy, what is the fattest tire one can fit on the front and back of a K75?
I want to go with the same size front and rear if possible, like the Japanese Cafes.

Tire Recommendations

escodsm wrote:3) With virtually all lights, gauges, speedo etc., removed - I cannot test fire this bike.  I bench tested the starter relay and it works well.  I have a brand new battery pushing 13.4V.  I ran 12V to the starter directly and the motor turned.
But with the key in the ignition all I get is a relay CLICK. Then nothing - the kill switch/starter button don't do a thing.
The turn signal switches produce a buzz from the relay.  (That I can see - with no actual bulbs there)

The start relay has two enable circuits -- the clutch switch and the neutral detection circuit in the instrument cluster.  Since you've removed the latter, the clutch switch is the only means to enable the start circuit.  The clutch switch is a N/C momentary pushbutton switch mounted at the clutch handle pivot that closes when the handle is pulled.  So pull in the clutch and try.  Or locate the connector under the tank to which the clutch switch connects and temporarily short the wires.

escodsm wrote:4) This bike had an alarm system on it.  I tossed most of it out.  The weirdest thing? Above the coils, there is that power outlet.  Above that, on the relay box, is a keyhole.  I have never seen this on any K bike online, anywhere.  I have the key for this but the stupid thing only turns half way, and you can't pull the key back out.
Backside of this key cylinder is connected to a lot of wires which I cut when removing the alarm system.  Methinks I cut something required here...

Ouch, I think you've done something bad by clipping the wires.  Maybe this was not an OEM alarm, but rather a third party alarm.  The OEM alarm connects into a plug in the relay box.  This sounds like the alarm might have been hardwired to the harness.  You may have some wire tracing and repair in your future.

Have you tried to follow the "Bike won't start" troubleshooting guide on this site?

Thanks robmack, 

But I *think* this is a factory alarm.  The box sat under the seat, on top of the computer module in that plastic tray.  It had a plunger switch that extended up through the cover for that tray.

When I get home tonight I will take some pics of the strange switch on the left side of the relay box.

I also noticed you ignored my #1 issue, haha, which was the frame mods.  Guess I am ok with it!

robmack wrote:


Have you tried to follow the "Bike won't start" troubleshooting guide on this site?

^^^^ Awesome Link, THANK YOU! ^^^^

I have seen most of the info from that link, spread thin all over the internet - but all on one page is pretty awesome.

escodsm wrote:But I *think* this is a factory alarm.  The box sat under the seat, on top of the computer module in that plastic tray.  It had a plunger switch that extended up through the cover for that tray.

From your description it sounds like a factory alarm, which is just a alarm
w/o a immobilizer circuit......so it's got nothing to do with your starting problems.

Inge, that is it exactly.  What was the plunger switch for?

escodsm wrote:Inge, that is it exactly.  What was the plunger switch for?

If someone tries to open the seat.........

Good luck escodsm, I really like the cafe look on the 750 with the shorter block. Hey Inge can you still buy the alarms ? what year did they supply them as a option from 84 I want one .
Halo

There's actually not much in that thread about the K75C and the bike in question is one of them with the narrow, drum brake rear wheel.

One good thing is that that might actually help the OP more nearly matching the tyres as both wheels are 18 inch, the front 2.5 inches wide, the rear 2.75. Both should take 120/18.

PICS!

Seat mockup:







Digital speedo:






Not a good pic, but here is that strange lock on the relay box:
(Find the fuses, then look left)





I'll take some better pictures tomorrow. 

Update for Monday Oct 7:
-I moved the tank over, and shorted out the 2-pin plug for the clutch switch.  No start, nothing.
-I threw my multimeter on same plug, and I got .20V when I push the starter button.  What's that mean?

When I say I got .20V at the clutch switch, I don't know what next step to take, based on this diagram:




I know the starter is good; I put 12V to it from a jump pack and it turned the motor over.


I guess that leaves "Bad clutch switch" or "bad ground" - but how do you explain the small trickle of voltage (.20V)

Forgive me if I am not converting that voltage properly, I know little about electronics.

G'day escodsm , that "lock" is the alarm activation key , I've got the same on my bike , as Inge K stated when you asked about the box thing under your seat , the plunger switch on the box activates the alarm if someone lifts the seat , it's factory

JR

JR, thanks mate, good to know. I hear from Inge K that this alarm type won't be interfering with much. Is that accurate?

Inge K is the man ! , if he says so I'd believe escodsm , having said that mine does not work anymore ( I think it has an internal battery that is ratshit ) and it hasn't affected the bike in any way

JR

escodsm wrote:When I say I got .20V at the clutch switch, I don't know what next step to take, based on this diagram:

I guess that leaves "Bad clutch switch" or "bad ground" - but how do you explain the small trickle of voltage (.20V)

Forgive me if I am not converting that voltage properly, I know little about electronics.

Between which two points were you measuring this 0.2V?

Disconnect the clutch switch from the harness and measure the resistance between the two poles of the switch with the handle pulled.  It should be around 0-2 ohms.  With the handle released, it should be infinity.  That will give confidence the switch is working.  Replace the connector.

If the start relay does not engage, it means the one side  of the coil is not being powered when the starter button is pressed (or the other side is not getting grounded).  So you should concentrate on finding out the continuity between the start relay coil and the clutch switch connector.

According to the schematic, one side of the clutch switch goes directly to battery through Fuse 5.  Test for positive battery voltage at that connection in the harness. If +12V is not measured, there are problems further upstream at the ignition switch or the kill switch.

robmack wrote:

According to the schematic, one side of the clutch switch goes directly to ground.  Test for that continuity to ground.  The other side of the clutch switch goes to the starter button on the right handlebar controls.  Test for that continuity next by measuring continuity from the start switch terminal to ground.  Each time you pull the clutch handle,  you should see low resistance, infinity otherwise.  





The schematic isn't correct, it's 12V+ at the clutch switch.

This have been mentioned to a certain person more than 1 year ago...

Thanks robmack,

I tested the clutch switch like this.

Moved fuel tank.

Disconnected clutch switch

Probed both poles of the female side of the disconnected
switch with pos and neg probes of my multimeter.

Turned ignition key to ON

pressed starter button and got .2v on my multimeter.

I did not test for ohms. I will do as you instructed and post results.

robmack wrote:

escodsm wrote:When I say I got .20V at the clutch switch, I don't know what next step to take, based on this diagram:

I guess that leaves "Bad clutch switch" or "bad ground" - but how do you explain the small trickle of voltage (.20V)

Forgive me if I am not converting that voltage properly, I know little about electronics.

Between which two points were you measuring this 0.2V?

Disconnect the clutch switch from the harness and measure the resistance between the two poles of the switch with the handle pulled.  It should be around 0-2 ohms.  With the handle released, it should be infinity.  That will give confidence the switch is working.  Replace the connector.

If the start relay does not engage, it means the one side  of the coil is not being powered when the starter button is pressed (or the other side is not getting grounded).  So you should concentrate on finding out the continuity between the start relay coil and the clutch switch connector.

According to the schematic, one side of the clutch switch goes directly to battery through Fuse 5.  Test for positive battery voltage at that connection in the harness. If +12V is not measured, there are problems further upstream at the ignition switch or the kill switch.

OK forgive me, as a newbie....I dont think I did this right.  But here goes:

I stuck the red probe of my multimeter into one of the female ends of the clutch switch on the harness.  Black to ground.
The multimeter shows a 1. Ohms set to 200 (?)
When I push the starter button, the multimeter jumps to around 100, then goes back to the 1.
IF I hold the starter button down, it does the same thing.

I switched the multimeter to Ohms 20k.  Now when I hold the starter button down it shoots up to between 900 and 1000, and stays there so long as I have to button down.

I'm guessing the difference between the settings is a decimal point?

There are 5 cut wires on my bike.  I just investigated.  I pulled all the relays out of the box without unplugging them so as to not mix them up.  There were two cut wires in there.  A brown, which is a ground, and another one.  I'll post pics up shortly.
Up at the right hand side control harness under the tank, there are three cut wires.  I will snapshot these as well.

The :factory: alarm key cylinder has two wires which meet up to a black plastic plug, with nothing attached to it.

I remember unplugging the big PIAA driving lights under the fuel tank.  But those ends are on the left hand side harness.  I dont know what was cut on the right hand side.  I did it so long ago that I cant remember.  Maybe the fuel level indicator and the oil temp gauge?

escodsm wrote:I stuck the red probe of my multimeter into one of the female ends of the clutch switch on the harness.  Black to ground.
The multimeter shows a 1. Ohms set to 200 (?)
When I push the starter button, the multimeter jumps to around 100, then goes back to the 1.
IF I hold the starter button down, it does the same thing.

Perchance, are you testing continuity with the circuits powered up?  If so, please don't do that.  You can do some serious damage to either the test equipment or the circuit.  I had made an assumption that you would conduct voltage measuring with power and continuity measurements with the battery disconnected.  Continuity tests will tell you if the integrity of the wires is maintained; voltage measurements will confirm that power is being applied to the correct parts of the bike at the correct time.  When testing continuity, its a good idea to try and isolate the circuits you are testing from all other circuits, where possible, to prevent leakage from throwing off the measurements.

I can't make any comments about the cut wires.  I've never seen or worked with the BMW alarm system.

Are you referring to the simplified start circuit published by Bert in the Troubleshooting URL above.  It helps you to visualize your target state and strategize how you will isolate components until you find the failing one (which is the whole intent of my description above).  Like Sherlock Holmes, “Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.” (or the source of your problem).

 
continuity is the setting on the multimeter that beeps when it's good right? 

Yes I only do that with no power.  But I thought I was to measure for voltage going to/coming from the clutch switch?

Let's ignore for a moment my poor electronic skills.

Wiring pic 1

Wiring pic 2

Wiring pic 3

Wiring pic 4

Wiring pic 6

Wiring pic 7

There are wires sliced from the right control cluster connectors.  You certainly have a task facing you after seeing those pics.  There are so many mods to that wiring harness, that I'd be tempted to get a whole new one.  Motobins has K75 ABS main harness on clearance for only GBP 40.00.  That's a bargain and well worth getting (if it works on your year of K75).  Or check Ebay for offers. It will save you lots of hassle.

That is a bargain but, are they tested and not hacked up? I see what your point is, but I could end up in a similar situation again.

I want to know what these wires are for so I can bypass or fix.

They are brand new harnesses

Hi, very interested as I'm in the process of rebuilding a K75C as a cafe racer. Questions:
1. where did you get the seat from? Something made up by yourself or purchased?
2. and where did you find the speedo?

thanks

Here is the speedo
http://www.ebay.com.au/itm/Digital-LCD-Odometer-Speedometer-Tachometer-Motorcycle-With-Backlight-csu-/390674566949?pt=AU_Motorcycle_Parts_Accessories&hash=item5af604cf25

Thanks RickG and robmack. Brand new harness - that's incredible. I have a non ABS bike is that ok?

Yeah it would be OK just tuck the ABS plug out of the way

jjefferies wrote:Hi, very interested as I'm in the process of rebuilding a K75C as a cafe racer. Questions:
1. where did you get the seat from? Something made up by yourself or purchased?
2. and where did you find the speedo?

thanks

jjefferies,

RickG hit the nail on the head with the speedo....haha. I wonder if I bought it from that same vendor.  It was a while ago.  I will do a complete write up on it when it's time to install.

As far as the seat goes, Dime City Cycles offers a large variety of styles of fiberglass seats.  True diehards will only settle for steel though, I just have no money and can't afford a stainless steel seat.

Take measurements first.  Our K bikes have a very fat rear, and most fiberglass cafe seats seem to be designed for skinny Japanese rear ends not German ones. Haha, there is a joke in that somewhere.  I chopped off the rear seat loop right up to the shock brace, but kept the cross member where the stock tail screwed into.

Oh, and RickG - - I'm about to press Purchase on the Moto-bins site for the wiring loom.  It DOES say (K75 7/1993 and up).  Do you think that is a problem for my 1987?  (I think it should be fine based on my automotive experience, but just making sure from a pro)

I cant think of anything that will cause problems. BMW give the same electrical circuit for all the K75s with add ons for ABS and the electric screen on the 95 RT.

Niiice.  It's on its way.  Thank you everyone!!

Updates when I have the new harness installed.  Should be pretty easy.  I've done it on Honda and Mitsubishi autos

Before loom comes in. The BMU relay is shot. It just buzzes loudly when I put the turn sigs on.
Would that have anything to do with the starting issue?

HOWDY 

I'm back....it's been 2 years almost...but I still have this bike.  I got the title all set and ready to go.  I also found out a LOT more since I've last logged in to this forum.

I got a Chilton manual for the bike (hey, it was free)

My rad fan is frozen solid - wont even turn at all.  

*AND*

Figured out the non starting issue....mice took up accommodations under the airbox behind the radiator in the years before I got the bike - and chewed the coolant temp sensor wires off.  THAT'LL DO IT!

So now that I am back in project mode, I will be visiting to update this thread as I get her back up and running.  I won't have so many ignorant newbie questions any longer, as I have my father in law in the garage working on his 1969 BSA Thunderbolt.  

Thanks to everyone who chipped in 2 years ago and put up with my derpitude

-Steve

Welcome back.....

That issue with the fan is well known. Mostly in cooler areas due to non use. My LT fan failed and I just killed the engine in traffic. But 35c in France and it was running even while moving in very slow traffic.

Thanks, Great to be back!

I'm planning on buying an aftermarket rad fan and hooking it up to 12v with a switch so I can turn it on manually if needed.
It just seems like a waste to spend $50-$100 on an original one if they are lousy anyway.

There are not many 'other' choices out there unless you work out how to wire in a coupla computer fans. Even the generic low profile 7" fans on eBay don't fit without mods due to the water outlet, hoses and metal shrouding on the front of the frame getting in the way.

But please let us know if you come up with something.

Thinking about something like this:

Universal 10" Rad Fan

Look closely back there behind the radiator. Where will you mount the thing? It can be no larger than 7" maximum, including the shroud, unless you push the radiator forward to allow clearance (not likely) or place it at the front of the radiator and either reverse the fan blades or change the polarity. This is my struggle right now with the Big Block K100/K1200 I'm building.

8" diameter 4" deep version

How I plan on mounting it

Simple, really - this one is 8" in diameter and will fit even better.  The whole thing is 4" deep where the stock fan has a massive motor sticking out 7" into the frame, behind the radiator.  There's two wires - a hot and a ground.  I'm going to cut the plug end off the stock wiring and tap into that.  Good as new.  It disturbs me that the Germans couldn't build a fan assembly that didn't fail.  Like having no engine oil dipstick on a Mercedes Benz C300.....(true story)

Everyone likes pics, so here is one I took yesterday after cleaning out the mouse house.  I don't know what I am going to clean that aluminum with, it is stained with years of mouse excrement    You can clearly see the as yet untouched coolant temp sensor wires, and what the little $*$&&%s did to it.  

I bought the same fan. There is not enough room side to side in there behind the radiator. The problem isn't one of motor height, it's of shroud width.

I used this fan on my K100RS.  Took about an hour to remove the tabs around the perimeter of the frame, pop rivet it into the old fan's mounting frame and bolt it to the radiator.  Add another two hours or so of screwing around with the fairing. radiator, hoses, etc. to do the whole job

http://www.ebay.com/itm/SPAL-USA-6-5-Straight-Blade-Low-Profile-Cooling-Fan-12-Volt-Puller-PULL-/301723133219?vxp=mtr

Here's a link the thread on fan retrofits that was my inspiration.

http://www.motobrick.com/index.php/topic,4313.0.html

The good stuff starts at post #18 on December 20, 2014.

That's the fix!

Thanks Point-Seven-Five, and Two Wheels Better

OK so my choice of fan was off....I trust your experience....wow 6.5"? I could have sworn it was 10 or 8.  

I have new wire spliced into the temp sensor, going to try it tonight, see if I get anything.  

Also, I will update soon with complete pics of the bike as it sits now, I see that my original pictures up the top of this thread have been lost (I changed my host a while back)

No start persists

Just an update - I have a brand new battery, fully charged.  When I jump the starter, it works.
When I connect the battery, the horn works.  
But nothing else.  :cyclops:

Here is what is disconnected.  Perhaps this is causing a no start condition.

1. fuel tank
   
2. air meter
   
3. gauge cluster ( but I DO have pins 5 & 6 jumped )
   
4. no flasher relay (it is missing - the large olive drab relay)
   
5. no coolant (fan and radiator are off)
   

All I want is to press the start button and get a signal, I am obviously aware with the above items not connected, the bike isn't gonna run .  

I have connected a voltmeter and I get 13+ volts at the start button.  When I turn the key to ON, I hear the starter relay click (or something in there coming to life), but the only thing that responds to my input is the horn.

When you turn the ignition on you're hearing the load shedding relay.

Best bet would be to follow the troubleshooting starting directions.


Starter motor gets its power via the starter relay. If you're not hearing this relay click when the starter button is pressed then the contacts may be fried. You can open the relay to check.

Starter motor may not be earthing properly.

Also, just check your emergency cut-off sw. is in the up position.

Another common problem is the plug on both the ICU and FICU can come loose and you aren't getting proper contact.

I've just re-read this whole thread and had a bit of a think about this and I think my post abouve would not be much help.

Two issues I see with the temporary setup-up you have is that you have no water temp sensor or MAF sensor connected. What this means is that both sensor circuits will be open ie: no signal at all to the ICU, FICU or temp switching unit. I'm not really sure how these units would interpret that but my guess is that it would shut the start system down so the engine could not run, because without those sensors the FICU would not be able to manage the fuel injection within set parameters. Open circuit (infinite resistance) would likely be outside the set operating range for the FICU.

um just an observation

you disconnected the fuel tank ? 

this is an efi system and requires the fuel pump to be running to get pressure to the injection system

as captain has said you also need the air meter in there as well

"bean old boy" successfully started his k100 without the air meter attached to the plenum ...but the wiring to the air meter was intact ...bit rough though

don't forget that the instruments also provide a signal when neutral is selected off to the ignition controller under the tank which then inturn provides a signal to the starter motor when the push button is pressed



I guess you could pull the clutch in to override this signal

just a heads up ...and not hard to get those things happening for a start ....or at least ...some fuel flow into the motor and possibly a starter motor turn at least

cheers  ...keep at it

Thanks Kaptain and charlie!

I do my share of automotive repair and also have experience with motorcycles - Japanese though.... like I said I know I'm not going to get the K running in the condition it's in...I just want to get a signal to the starter without having to re-install everything over and over.  

There is a brand new starter relay for those who don't want to go back and read this whole thread.
The starter does kick if I juice it with a charge pack.
there is no instrumentation, it was all sold away.  I have pins 5 and 6 jumped per instructions on this forum.

This weekend I will install the fuel tank, air meter, and yes make sure the ICU box near the forks is plugged in all the way - that little bugger loves to pop out.

Also - pictures! I promise.  Not because it's anything "awesome" but, everyone loves visuals.

just to add a note if you haven't already read about it

the fuel lines from the tank to the injector rail can be extended just a bit  couple of inches perhaps ....which leaves room to lift the tank and do work ...without undoing the fuel rail every blooming time
 the tank electrical connection  is easy to access  so no issues there ...unless the socket part of the plug has corroded ...or widened and doesn't make good contact

good luck

To add to what the Kaptain was saying - I know my K100 wouldn't run with temperature sensor plug detached. I assumed this was due to the FICU seeing this as an over temperature situation sufficient to warrant shutdown. My recollection was I could get it to kick over / fire up but that it would not run

rawdonball wrote:To add to what the Kaptain was saying - I know my K100 wouldn't run with temperature sensor plug detached. I assumed this was due to the FICU seeing this as an over temperature situation sufficient to warrant shutdown. My recollection was I could get it to kick over / fire up but that it would not run

im sure you meant "under temperature " situation rawdon ....remember the temp sensor is high for low temp   ...so infinity is close to - 273dec c ?  lol ...where as .. if  it approaches 0 resistance (short circuit )  the ficu would shut down with over temp signal .

ill bet it was pumping heaps of fuel that it couldn't ignite ...ill bet you knew that ...but like me, I forget things as in typing ....trip ..face plant ...shoot ...bugga