I received this from a friend with problems..any ideas lads?

Hi Allan,
Yesterday, as I was leaving for town, the bike suddenly died on me ...no ignition, lights, nothing. I have checked fuses and snap-on connectors and they are OK.
When I rode down from Bethlehem in pouring rain last year in May, water got into the instrument nacelle (?) which I opened and cleaned but lost the clock.
The other problem was that when changing gears in the rain, the gear selection indicator was jumping from gear to gear and eventually showing the wrong gear eg, neutral was showing when I was in 5th. When I tried to start the bike the following day, it would not turn over in neutral but would do so when I pulled the clutch in. The neutral contact on the gear selector switch had obviously been compromised and perhaps the clutch over-ride contact has eventually succumbed. Anything else you can think of?
Regards, Frank

I am baffled, Ajays

Check the fuses with a meter I have seen some in the last few years go open circuit without showing they have blown.
The other problem sounds very much like the gear position switch is wet inside, they often dry all by themselves. If not he will need to remove the swing arm and take the switch apart.  They often sucumb to age as all of us do. The rubbery sleeve will crumble away fairly easily then the switch can be disassembled but do it in a plastic bag which catches all the small springs and balls. Sometimes just leaving it out in the sun while you clean up for a spline lube it will dry out then encase it in sika flex which is a polyeurethane glue similar to silicone but is permanent.

a pretty common issue ajays

if the gear selector switch becomes faulty ...and many do with the ingress of water from a dilapidating plastics at the gear position switch at the gearbox

the issue of starting does become an issue

the clutch activation overrides this ....could be till that switch also becomes faulty ?

I have had to replace several like switches ...eg front brake switch  and rear ...which are the same item as the clutch switch

the thing that concerns me is that the meters has had some infiltration of water ??? and resultant corrosion ?

this could affect several things ...but first that comes to mind is the start enable circuits that comes out of the instruments ..(for when neutral is selected )




lets hope that the instrument electronics hasn't been compromised by now corrosion
 
could the issue inside be a contributing factor ?

there have been quite a few contributions to resolving the neutral switch issues ...including replacing the switch ( the switch contacts connect varios terminals to ground   and decoded in the instruments )

you might remember scp  installed some resistors in parallel with the switch contacts ...which wetted the contacts ...for a more reliable operation on the gear indicator switch

..im a little confused as to your mates actual description as to what in fact is at fault

but I hope this helps some

cheers

Thanks Lads for the help, I have passed on the info;

Things do start to pack up with age, in my case its the legs go first especially the middle one!
                               Ajays

charlie99 wrote:
..im a little confused as to your mates actual description as to what in fact is at fault

Agree. Probably two separate problems.
The start interlock circuit is one issue but I don't think it would cause all the electrics to die once the engine is running. That sounds more like the ignition switch to me

Cleaning a BMW K bike ignition switch

Only now had the time to have a look at the problem.
I strongly suspect that the Gear Selector Switch on the gearbox is the culprit. When I rode 600kms in pouring rain the gear indicator on the speedo console was occasionally flashing from gear to gear while I was in 5th and sometimes showing the whong gear when changing up...water got into it(?) although I can't see how. Also, water got into the speedo console which resulted in the clock not working any more and the bike could only be started with the clutch lever in...not when in neutral.
Looks like to change that switch one has to remove the swingarm which I definitely do not feel like doing. As per the attached sketch of the connector going to the gear selector switch, if I were to short the brown wire (earth?) with any of the three remaining wires I should be able to bypass the switch and restore a circuit...not so? I am not too good on electrics but this seems to me to be correct. A number should appear permanently on the console but that is not a problem. Whether I will regain the Neutral start is debatable but not serious.
I suspect you still have a wiring diagram for a 1986 K100RS if not I can email a copy. Waiting in anticipation.
Damn computer does not want to attach so will have to describe.
There are four holes in the form of a square:
Top left is Yellow.
Top right is Brown (earth ?)
Bottom left is Yellow/Black
Bottom right is Blue/Yellow
QU: How come four wires for five gears and a neutral?

The switch has four wires because the switch is outputting a binary number representing the currently selected gear.  In binary, three digits can represent up to 8 decimal numbers, from 0 through 7.  Neutral is zero, and the other gears are their respective binary representations -- 001 = 1, 010 = 2, 011 = 3, etc.  The fourth wire is ground, which provides the source potential for representing the "0"s.

Reference: http://www.ibmwr.org/ktech/trans-switch.shtml

Thank you Robmac very informative and helpful and thanks for your time.
He should be able to solve it now.
I think he was looking to isolate the switch completely so he could use it without having its use.
We shall see the  result and will pass on the info;
 Ajays

'ol Brian Curry sure is a fountain of knowledge. Is the Austrian from Salzburg, the "professor" in the white dustcoat still contributing to the forum?
I am about to have a lie-down (13h58) and digest the information. Thanks again for your help. Frank

The answer I received from my SA friend I thought you would like to see, he is very grateful, thanks all.
                                  Ajays

from my south african mate/
Hi Allan,
Happiness! Cleaned out the Fuse box and Selector Indicator snap-connecter with Electrical Parts Cleaner; replaced folly charged battery and Voila!
I did first of all do the VOM check and would you know, they ALL gave a reading with brown earth in all gears.  (??)  Anyway, the indicator shows the correct gear engaged but I still can't start in Neutral. This however is not a bad thing, as it now becomes a secret ignition cutout which will have any would be thief guessing as to where the hidden cut out switch is.
Thanks again for the forum assistance and happiness is a running machine! Frank

You have done it again fellows....thanks...Ajays

Had the same problem myself with the switch not the best place for it, good to see you on the forum again AJAYs
hope you are keeping well.


BIG D

https://drive.google.com/file/d/0B3cEQcXAESQBbEk3bkduUDJFeVk/view?usp=sharing

Sold to a man with a trailer when I moved to Kent recently.
                                  Ajays

This is a way of getting the gear position switch to do what it's supposed to do. 

Been working on both my K's for over 25 years.

https://www.k100-forum.com/t6936-gear-position-switch

Paul.