I bought this half converted cafe project a month ago (85 K100RS) and it has been starting and running just fine since I bought it.  The owner claims it has 18,000 miles and has been in his family since new but it has no instrument cluster (cafe project...).

Today the bike started fine and I rode it maybe 5 miles to breakfast and it wouldn't start when I was trying to leave.  The little green starter button has always felt like it was missing a spring inside (it doesn't have a solid spring back when you push it in).  I'm curious if while riding it's making contact on/off all the time and that burned something out...

I was able to push start the bike and get home.  Same deal when I got home and tried to restart it.  The battery has 12.78 volts when the kill switch is in the "on" position (or any kill switch position really when I'm probing directly at the battery terminals).

I pulled the switch off the bars and opened it up and can see where the green button's backside (a metal button) connects two halves of a continuity ring.  The right side of the ring (away from center of bike) has 0.16v and the left side has 0.57v.  When the button is pressed and connects the two, both halves then have 0.57v.

That seems like almost no voltage at all.  I plan to buy new switches for both sides (the left turn signal lever is broken off anyway) but was wondering if anyone could guide me to the next step.  I can see a bunch of relays under the rear of the tank but I'll have to figure how this custom seat comes off to get at them.  Any tips on lifting the tank as well - it is about 1/3 full of fuel and it looks like the hose leading to the fuel rail will not allow the tank to lift up much..

TIA!!

Pic of the bike:

Tank arrangements were changed on the Ks.....since yours has been altered cant tell from the photo.....is the power connection into the tank located at the front left of the tank or the rear right?

Also there are two hoses, not one, The front one is the one to the fuel rail and you should replace with a longer one.

When you try to start does the engine turn over and not fire or simply not turn over at all?

Olaf, Check the photo by clicking on it to view the big image. It's an early tank because you can see the pump connector on the front left between the hose connectors.

Does the starter turn over or the bike start if you pull in the clutch?  If so, there's a problem with your neutral detect circuit. Since the OEM cluster is missing, I'm assuming the PO did something to duplicate that function and there could be a problem there.

With the ignition on and the clutch pulled in there should be +12V on the Black/Green wire (Pin 6 on the under tank connector for the right hand controls).  If you're reading essentially nothing, then the Start Enable signal is not getting through.  Check Fuse #1 also.

Bike has started and run normally for the month I've had it until now. 

To answer the question, nothing at all happens when I press the button.  No crank, no start, no click (I work on cars a bit - what I mean is no starter solenoid type click).  Doesn't matter if I hold the clutch, or it's on the center stand (and it used to start just fine either way).

Again, whatever happened just now, is not because of the missing cluster.  The previous owner must have done something with the starting circuit (if you have to), because the button has been starting the bike just fine for the last month (although the button itself never quite felt like it had a spring behind it).

See if putting 12V+ to the black/yellow wire at the right combo switch connector gets the starter going. (That's the wire that sends power to the starter relay when you hit the start button.) 

On a bike with a factory cluster, either the N light in the cluster or the clutch switch sends 12V to the start button. (Via black/green wires.)

To answer the question, nothing at all happens when I press the button.  No crank, no start, no click (I work on cars a bit - what I mean is no starter solenoid type click).  Doesn't matter if I hold the clutch, or it's on the center stand (and it used to start just fine either way).

As Duck says... what you are describing will happen if no neutral light or failed clutch switch or no clutch switch.

Although you pull the clutch you need to be sure the switch is actually still fitted and still connected to the loom under the tank. But the right hand switch gear could also be disconnected, can you confirm if lights come on and indicators work from the right hand side?

I hadn't looked at the large size photo to see the electrical connectors at the front of the tank, but if that's gone wrong it doesn't stop the engine turning over.

I'm at work but I'll get a look at it tonight, hopefully.

I did not check to see if the turn signal works... I can do that, otherwise there is no cluster for me to look at indicator lights.

On what I think is an unrelated note, the custom headlamp has also worked fine until recently.  Maybe 1-2 days before the no start condition, the headlight would not turn on (and still doesn't).  I haven't investigated it since I rarely ride at night (of course not at all now).  I have plans to do a vinyl wrap on the tank and was going to investigate all this stuff when I had the tank off for that, but now that it won't start, I need to bump up the time frame

Thanks for all the suggestions.  I'll post back as soon as I have time to do some testing.

Re lifting the tank you will see at the back of the tank, under the very front of the seat there is a flat plate same colour as the tank. Its held on with a single 10mm bolt. You can see it from the side.

Undo that bolt and slide the tank back and then you can lift it off.

First before you move it  you must unplug the electrical connection and the front left and disconnect the two fuel lines.

Be careful wriggling these off the tank spigots, excess force will break them off.

You probably need to renew the fuel lines, Make them longer so next time you can slide the tank back enough to access the coolant filler cap and also lift the rear enough to access the electrical relay box without having to disconnect them.

One easy thing to do before unbolting everything is to put a voltmeter on the starter terminal to see if it is getting 12+ when you push the start button.  If you do then all of the other checks will not be needed since your starter would be the problem.

1. Turn on the ignition and test the voltage at the Green/Yellow wire on Fuse 1. If no voltage, either defective kill switch or defective ignition switch

2. Replace Fuse 1 with a known good fuse irrespective of whether the current fuse is good or bad.

3. With the ignition still turned on assuming the above test passed, measure the voltage at the Black/Green wire on pin 6 of the right hand switch cluster under the tank on the right side while you pull in the clutch handle AND/OR you have the transmission in neutral. If no voltage, either no clutch switch, bad start enable circuit, or defective wiring.

4. To eliminate the wiring as a problem if the above test fails, measure the voltage at the Green/Black wire on the Connector for Special Instruments under the tank on the right side. If you measure voltage, wiring is good, the one of the other items are bad.

5. If the test in Number 3 passes, measure the voltage on Pin 1 of the right hand switch cluster (Black/Yellow). If no voltage, defective start switch. If voltage is present, probably a starter relay problem.

Will try these things but looky what i found over on motobrick!


Re: Backspin Starter Maintenance #1 Cause Of No Start -N- Electrical Whack
« Reply #12 on: April 09, 2016, 12:54:54 PM »

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1... moto on center stand with side stand up...
2... ignition key in the off position...
3... kill switch in the run position...
4... turn key on...
       a) have no headlight...
5... press the start button...
       a) no start and no headlight...
       b) start and no headlight... 
6... swap your horn relay for the load shed relay... 
       a) if gotts headlight proally load shed relay... 
       b) if still no headlight proally the starter needs cleansing or needs new brushes... 


Maybe it's not coincidence that my headlight went out right before the no start condition happened!?  Do the headlight and the starter share some electrical path?

boostd4 wrote:
Maybe it's not coincidence that my headlight went out right before the no start condition happened!? 

In your future quest for answers to your bike's problems, try to give a complete description of the condition. The headlight's being out when trying to start could be a key element of diagnosis.

Anyway, this link could be instructive.

Sorry, my mistake.

With this being someone else's butchered cafe project before mine, there are many, many things that are either eliminated, or rigged to work.

Gonna give the "roll backward in 3rd and pop the clutch a few times" a shot before taking anything apart.  If that's enough to clean the starter brushes and everything works... well than hooray.

I've read conflicting info.. some state a bad load shed relay won't keep the starter from engaging - just might not be as effective as the accessories would still have full power.  Other's state it will be a no start condition if it's bad.

If the starter brushes are dirty would this keep the headlamp from working?  Even when the bike is running (after popping the clutch to start it?) - because I still have no headlamp when it's running.

boostd4 wrote:I've read conflicting info.. some state a bad load shed relay won't keep the starter from engaging - just might not be as effective as the accessories would still have full power.  Other's state it will be a no start condition if it's bad.

If the starter brushes are dirty would this keep the headlamp from working?  Even when the bike is running (after popping the clutch to start it?) - because I still have no headlamp when it's running.

The load shed relay is a symptom of a starter problem not the cause of a starter problem.  It will not keep the bike from starting or make it run bad.  It will turn your headlight and other accessories off if it does not activate but this could be the starter causing it to not activate.  If you have bad continuity through your starter this will cause the load shed relay to not activate and your headlight will not work.  It doesn't matter if the engine is running or not.

The easiest way to check your starter is to just put a voltmeter on the starter and check for 12+.  I don't know why everyone seems to want to check everything else first.  I can check for voltage on my 91 K100LT in less then 10 seconds.

Ok.  Pulled the ignition coil cover off and checked the starter.  There is only one wire to the starter that I can see (I'm guessing it's grounded through the body of the starter?) and it's black, secured to a post with a nut.

With the ignition on and killswitch set to start (or straight up - mine has no markings but this is the position it has always started in the past), I get 0.2V measured at the starter post (negative probe on battery negative post).  With probes setup like this I can see a minor change in voltage when I swing the kill switch to off, then back to start.  it goes from 0.17V to 0.26V (on).... basically no voltage but something in that switch is being registered at the starter.

I checked the turn signals and they work.  Well... the bike has custom rear turn signals and no front signals (the way I got it), and the rears work like they always have, flashing fast (because there are no front signals?, or perhaps aftermarket bulb resistance), but I can hear the flasher relay ticking away as they flash (if that helps).  Not sure if this applies to the load shed relay as the previous owner may have wired them up another way (?)

It's raining hard here and wasn't able to get it out of the garage to check the reverse clutch popping to see if that cleans the starter brushes.  Also could not get it out of where I keep it to start draining the tank and getting it out of the way to do all the wire checks suggested above (cars blocking it that I don't want out in the rain).  Will have to wait until tomorrow.  

Thanks again for all the help.  I'm excited to get the tank off and do some more testing.  If anyone sees anything obvious with the little info above, feel free to chime in.

boostd4 wrote:...Also could not get it out of where I keep it to start draining the tank ...

Shouldn't need to drain the tank to remove it.  I've been thrashing about fixing a leak at the fuel sender unit under the tank on my RS and had the full tank on and off multiple times in the last two days.  I remove the fuel supply line at the fuel rail, and the fuel return line at the tank on the front left side of the tank, disconnect the fuel pump/sender connection on the right side just below the rear of the tank, pop the two clips at the back of the tank holding it to the frame and pull back and off.  You get a bit of fuel dribble from the two disconnected fuel lines, but very little.  The first time might take you 10 minutes, and about 2 minutes any time after that, once you know the drill.

I have found that leaving the cap open will to a large extent prevent any fuel dribbling out as it prevents pressure build up as the fuel is sloshed about.

Success!

And both of my problems seem to be really REALLY stupid easy fixes.

Thanks above, I did not need to drain the tank and it was very easy to remove.  I assumed the fuse box was in the relay box under the tank (it turns out I didn't even need to remove the tank).

Fuse #1 was blown.  I replaced it with a good one and the starter turns over just fine.  The previous owner covered the fuse box with this gray metal mesh piece (see pic in first post).  The fuse box sits so close up to this that I didn't find it until I started following wires from the battery positive.

As for the headlight - instead of chasing connector wires, I first pulled the bulb (which at first glance appears good) and tested the socket connector for the bulb.  1 of the 3 posts has 12V with the switch on so power is getting to the bulb.  The bulb had no conductivity between any of the 3 prongs.  It looks like this is an HB2 bulb with a funky filament setup inside... one of the filaments looks fine but the other is likely broken.  I'll test with a new bulb when I get to work.

I guess the next question is "Why did fuse #1 blow?"  The hard part about a 30+ year old bike is that the answer could simply be "age."  I guess we'll find out as time passes if it blows the fuse again.

From what I could see in the relay box and the right side connector - it looks like the previous owner tapped into both green/black wires in that connector, joined them, and they go into the relay box into another wire (wish I had taken a pic).  So far everything works so I'm not going to mess with it.

Thanks for all the help guys.  My exhaust and custom seat and rear cowl have shipped.  I'll start a new thread with pics when progress moves along!

boostd4 wrote:I guess the next question is "Why did fuse #1 blow?"  The hard part about a 30+ year old bike is that the answer could simply be "age."  I guess we'll find out as time passes if it blows the fuse again.

I too used to live in the land of unicorns and the Easter Bunny, believing fuses could just "fail" for no reason.  Sadly, I have found that fuses almost always blow for a reason, and often it's not immediately obvious why.  It sounds like the PO of your machine did a lot of modifications in the wiring, and it may be easier to figure out who shot JR than what wiring modification is causing your issue.  For now have a few spare fuses on hand for the inevitable.

I'm still looking for my unicorn...

Has the fuse blown or is it just open circuit. I have seen many of the blade type go open circuit with age. It pays to replace them about every 10 years at a maximum. They may look good but when you put the trusty meter on them the truth comes out.
The OEM fuses which have the fuse wire showing are usually OK but the later and cheaper ones with the S shaped fuse inside the plastic are very troublesome after even 5 years.

kioolt wrote:One easy thing to do before unbolting everything is to put a voltmeter on the starter terminal to see if it is getting 12+ when you push the start button.  If you do then all of the other checks will not be needed since your starter would be the problem.

I had K100 not-starting a while ago and started it a few times by shoving a spanner(thick chunk of metal) against the two terminals on the output side of the starter relay. Also an "easy thing to do" I don't think it's a "good" thing to do, but in a pinch it's easier than a push start and it confirmed my theory that the starter relay was bad.

RicK G wrote:Has the fuse blown or is it just open circuit. I have seen many of the blade type go open circuit with age. It pays to replace them about every 10 years at a maximum. They may look good but when you put the trusty meter on them the truth comes out.
The OEM fuses which have the fuse wire showing are usually OK but the later and cheaper ones with the S shaped fuse inside the plastic are very troublesome after even 5 years.

 Fuse was obviously blown. It was one of the cheap clear plastic ones with the S shaped fusible link. It doesn't look like an age thing now that I think about it, the fuse was quite obviously split on the S-curve. I suspect my start button may be making contact while riding without me knowing it. I ordered a new switch directly from my BMW source, not too bad for $110.

If your engine is doing over 711rpm then the starter circuit cant work because the ICU removes the earth from the start relay.
Like .75 said if the fuse is blown then there is a reason so if it blows again then go a hunting and find out why.

Back from the dead! 

I had been hashing out some of this fuse blowing stuff on the Facebook K100 cafe group but I thought I'd add to this thread for anyone else who is searching.

For some reason, I had been blowing fuse #1 very randomly when I originally posted this.  I came to find that it would not blow in cold weather, but only in hot weather, and got worse and worse.

I figured it had to be a loose wire, because I'd replace the fuse and it would ride fine (all functions working that are related to fuse 1) for about 10 minutes of riding, then pop.

I jiggled wiring bundles until I found the left hand controls bundle would pop the fuse when I jiggled it.  Pulled the tank and found that if I wiggled the clutch switch connector under the tank, it would pop the fuse.  I ended up (for now), just cutting the connector out and wiring it direct.

The bike ran great for about 2-3 days, several hours of riding each day in hot weather.  Thought it was fixed.

Then Monday I rode it for about 2-3 hours with no issue.  Parked it in my driveway, then went to start it and it fired up and immediately popped the fuse (I thought it happened when I pulled the clutch in but not certain).

I pulled it into the garage and used my makeshift short detector (a headlight bulb with wiring leads ending in male spades to plug in where the fuse goes - if it lights up, there is a short).  I first put a new fuse in and turned the ignition on - the Acewell cluster made it through it's initial sweep then the fuse popped - I had not started the engine or touched any other controls.  I then plugged in my headlamp bulb to the fuse location and turned on the ignition - the bulb glowed very bright for about a second, then turned off and all the cluster and everything came back on!  Like the higher amperate/voltage the bulb allows was able to cut through a short/resisitance somehow.  ??

Very confused about that one.  I then jiggled every wire I could reach and I couldn't get the bulb to light up.  I put in a very small amperage fuse (5A) and tried again - still won't pop.  I pulled it out onto the wet driveway (it had just finished raining) and let it run.  It started normally and idled normally.  I revved it a bunch and used all the switches and I can't get it to pop the fuse.

I thought maybe it was resistance in the starter circuit so I did the "rolling in reverse and popping the clutch in 3rd" to clean off the starter contacts, etc.  I was not able to ride it because it was so wet (it's a naked bike and a menace to clean when wet/filthy roads).  I'll ride it tonight after work and see what happens.

Grateful for any insight on this matter.  I'm no longer of any kind of mindset that these things "fix themselves" as I've been replacing fuses all summer. But perhaps the starter circuit was causing this and doing the roll-back method fixed it of sorts?  I know the starter switch and kill switch are on fuse #1, not sure if the starter itself can affect this.

^  Appropriate last sentence.   I took the bike out for a ride last night for a good 30 minutes.  Rode her hard and hot and used all functions and everything worked as it should.

Got up this morning and got on it to ride to work.  Got about 2 blocks from my house when I looked down and noticed the Acewell blank/dark, fuse popped.  WTF.  I didn't see it happen live, so I'm not sure what was going on when it popped.  I do know it still had the 5A fuse in it (should be a 7.5A) but it rode all last night without popping.  I'm stuck putting the 7.5A and riding it again to see if it pops.

At this point I still suspect a bad clutch switch at the trans.  When I was short-testing originally, I would occasionally see a wisp of smoke come up in the area between the tank and the seat from below ....   the clutch switch is down there, but so is the gear indicator switch and side stand.  I could actively make the fuse pop by wiggling the clutch switch connector under the tank so I eliminated that, but perhaps the switch itself is shorting and melted the connector first?

I need some clarification as to what empty plugs I have under my tank go to.  I'm going to eliminate the heated grips connector (don't have 'em), and the clutch switch (don't need it).  I'll take a pic tonight after work.

This is a frustrating one.

Just wanted to thank Robmack especially "change fuse 1, irrespective...". I had the same no start issue and I have been trouble shooting my wiring for days with no luck. I tested fuse 1 in place and it was ok. I am assuming that when I probed it, it would close only to open when I took the probes off. I followed the change it advice and what-do-you-know. No more issue!
Thanks to you all!