Questions at the end of my Cafe Build

[Froader4life]

So my 1984 K100 Cafe is almost done. The to do list is pretty short but I do have some questions that you guys can probably help with.

First, I have a custom cluster but wanted to utilize the coolant over temp alert. So I have a simple LED with power and to one end and the wire from the coolant sensor going to the ground. The problem is that the LED is on all the time. I figured the coolant sensor would ground out once the coolant temp was too high.

Second, I did the 3 relay trick to emulate the stock cluster so I can start my bike in neutral and I also have a LED warning light for neutral. The problem I'm having is that when ever I pull in the clutch the light goes on even when I am in gear. I want the light to come on only when the transmission is in neutral.

Lastly, I already did a search and I believe I found the solution to my headlight switch not working even though the flasher does. Sounds like a bad switch.

Anyways, this forum helped me big time to get this bike that had been sitting for 12 years to the point it's at now. So thanks everyone.

[Inge K.]

The high temp warning signal don't come from the sensor but a relay (middle RHS in the relay box).
From terminal A3 on this relay it's a violet/black wire to the old cluster (if you still have the old wiring).

About the neutral light, after the relays/bulb you must mount a diode to block the current from the
clutch switch.

See if you can get a newer filler cap at the tank, the one you now have is known to let water through
(find one w/o the push button)........on the first picture it also sems to be mounted the wrong way around.

[billday]

This is a beautiful build, congratulations.

How does it handle with the forks dropped down like that?

[Elipten]

I would like to know more about alternate fuel caps.

[Froader4life]

The high temp warning signal don't come from the sensor but a relay (middle RHS in the relay box).
From terminal A3 on this relay it's a violet/black wire to the old cluster (if you still have the old wiring).

About the neutral light, after the relays/bulb you must mount a diode to block the current from the
clutch switch.

See if you can get a newer filler cap at the tank, the one you now have is known to let water through
(find one w/o the push button)........on the first picture it also sems to be mounted the wrong way around.

I did use that violet/black wire as the ground. Most sensors turn into a ground when it is activated and there is positive going to the light at all times. This light is constantly on now so for some reason that sensor is already grounded. Any other ideas?

For the neutral light, which wire needs the diode?

I know for a fact that the fuel filler cap is on the right way. I can tell because of the hole for the vent which is obviously the issue with getting water in the tank. Since my bike leans the other way now on the sidestand that hole is high while it sits, not that I plan on having this thing sit out in the rain ever. I would love a new non-locking cap but I haven't been able to find anything anywhere. Anything I find has 3 bolts, my cap is mounted with 4 bolts.

[Froader4life]

This is a beautiful build, congratulations.

How does it handle with the forks dropped down like that?

Thanks for the kind words.

I never got to ride it in it's stock form but based off riding other bikes it's fine. No issues. The front is a little too soft for my liking so I might have to do something about that. But I did lower the rear as well so the rake and other geometry should be pretty close to the same.

[TimTyler]

What are those two extra holes in the valve cover?

[Inge K.]

I did use that violet/black wire as the ground.

Then it could be that this wire is shorted to ground somewhere between the instrument connection
and the relay.
Or it is something wrong With the relay.
Or the relay is receiving wrong signal (wire or sensor shorted to ground) from the sensor, but if so the fan should be turning all time, too.

For the neutral light, which wire needs the diode?

After the relays/bulb, before the connection to the clutch switch.

, not that I plan on having this thing sit out in the rain ever.

But I Guess you gonna wash it now and then.............if so but a bit of tape over the push button.

[Inge K.]

What are those two extra holes in the valve cover?

Oil drain plugs, on the very early models.

[Froader4life]

What are those two extra holes in the valve cover?

Oil drain plugs, on the very early models.

That's funny. I've never even noticed that all the other bikes didn't have those drain plugs.

[Froader4life]

About the neutral light, after the relays/bulb you must mount a diode to block the current from the
clutch switch.

I still have no idea where to put the diode. I have tried it off the clutch switch and off the relay. Noting is working.

[Froader4life]

Never mind. I'm dumb. Got it now. Neutral light is working as intended now. Thanks!

[Froader4life]

Ok...now as far as that coolant light being on, it's actually the fuel light that's on. First I had the brown/black wire going to the warning light but it stayed on all the time. So I switched it over to the brown/white wire. Still on. I know I have almost 3 gallons of fuel. Neither one of the wires are showing to be grounds when I test continuity. Wtf is going on?

[Inge K.]

The fuel level sensor using two thermistors inside the tank for the low level warning.
You also need the PCB inside the old cluster for a proper function.

[Froader4life]

The fuel level sensor using two thermistors inside the tank for the low level warning.
You also need the PCB inside the old cluster for a proper function.

Is there no other solution? Could I get a PCB at an electrical warehouse like Fry's Electronics?

[Inge K.]

Is there no other solution?

Not any easy and simple way, what I'm aware of.

One is the earlier mentioned PCB, which is a BMW specific part.

Or search a tank from a later model (-86 on) which have a different level sensor,
but then you also need to weld new mounting brackets to the frame and some minor
changes in the wiring.

[rbm]

Is there no other solution? Could I get a PCB at an electrical warehouse like Fry's Electronics?

The following circuit published by Marukitano over on Flyingbrick.de will do what you want.



Inge's right; there's no easy way, but there is a way.