My gauges stopped working, so I installed a digital speedo with the sensor, which is cable tied onto the side of my handlebars. Now I want to remove everything and connect whatever I can to the digital one (it's a Koso DB-01R).

The problem is that my electronics abilities are limited to testing for power to the wires and soldering them sloppily together. That's it, although I'm willing to learn.

Since I'm making a cafe racer I want the absolute minimum legally required by Austrian authorities. So, I don't need hazard lights, heated grips, temp gauge, RPM indicator..... what else could I eliminate? Fuel gauge would be nice though, but how hard is that to wire into the Koso if I was to remove the big one?

And for the things I do need to pass inspection (high beam, turn signal, neutral... anything else?) what's the easiest way of wiring them?

I read that the alternator doesn't work if I remove the original gauges, is this true? What's the simplest way around that?

I know, it's all over my head, but I don't mind failure.... it's the only way I'll learn anything.

Read "Messing with the in-tank fuel sender" to see what you can do to get the fuel sender working.  Hopefully the DB01 is programmable.

Make an exciter circuit from a couple of 56 ohm, 2W resistors to replace the charge indicator light that disappears with the OEM gauge removal.  Connect it to a source of switched 12V and the other end to the blue wire on the alternator.

Read my blog to see how I handled the wiring on my K75.  URL is in my signature.

Thanks, but as I said, I'm completely inexperienced with electronics, so that fuel thing will be impossible for me.

Would be great to have a step by step for making this exciter circuit, showing where I can find the right cables and where they go. It would probably also help other noobs like me who want to replace the OEM gauges (they all fail eventually from what I have seen).

This diagram shows the schematic.



I'll explain.  The switched +12V is picked up off the Green/Black wire from Pin 6 of the cluster.  The two resistors (R1 & R2) are serially connected to that wire.  The Blue wire from Pin 9 of the cluster is connected to the other end of the resistors.  No additional cables are needed.

The part about the gas gauge is mechanical, not electrical.  I describe how to flip the board in the sender to make it work with Far East gauges like the Koso.

If you're going to tackle a major rebuild like a cafe, you're going to have to jump in with both feet and learn electronics.  The K-bike is full of them.  How else were you planning on debugging problems without such knowledge, especially when you have to modify wiring.  There's no recipe for where you're going with this build unfortunately.

Thank you! This is much more understandable to me.

Of course I'm willing to learn about this, and nothing gives me more joy than having a problem to solve, and slowly working at it bit by bit.... isn't that what life is all about?

This is my second K100, so I know the bike quite well inside and out, it's just some of the more technical electrical things that I need guidance of wizards like you.

More questions to come.

Can you walk me thru how to get the instruments off my k100rt? It's an 85. Once off I am familiar with the boards and such but never removed a set.

Procedure is documented in Section 62 of the BMW Service Manual. Available online in the download section and also at Motobrick

Thanks!

What is a good way of testing to make sure it works after I've done this?

Test as you would for any working alternator. Using a voltmeter, look for 13.5V - 14V across the battery terminals with the engine running above 2500RPM.

I found this on another thread. Is this the easiest way of getting the neutral light to work? Where's the best place to put all these relays, will they fit in the relay box under the tank?



Also can I route the cables 15/high beam and 17/19/turn indicators directly to the lights on the speedo unit, or is there anything special I have to do?

The project has begun, I took off all the plastic and radio the other day, but since the bike is in a friend's garage kind of far away from my place I have lots of time to premeditate my next moves.

Actually could I just connect the alternator cable to the oil temp light on the new gauge? Wouldn't that do the same thing?

gringoloco wrote:I found this on another thread. Is this the easiest way of getting the neutral light to work? Where's the best place to put all these relays, will they fit in the relay box under the tank?

1) cheapest solution?  Definitely.

2) The relays don't have to have large contacts to carry high currents, so you're free to choose physically small 12V DC relays with 1A contacts, for example.  These can get pretty small, meaning if you have electronics skills, you can build a printed circuit card that fits in the relay box.  I've built this circuit for another guy on the forum using four small encapsulated relays.  I glued the relays together using epoxy and soldered the wires directly to the terminals, providing pigtails to connect to the bike harness.

gringoloco wrote:Also can I route the cables 15/high beam and 17/19/turn indicators directly to the lights on the speedo unit, or is there anything special I have to do?

Yes, you can. Nothing special except ...

CAVEAT!!!!  Different aftermarket gauges have different indicator light arrangements so you have to make sure the gauge you select has ACTIVE HIGH indicators.  This means you provide 12V at the gauge to turn the indicator on, ground to turn it off (because this is what signals the K100 electronics will supply).  If the gauge you select has ACTIVE LOW indicators (ground to turn on, open circuit to turn off), you'll have to come up with a way to invert the signals on the bike.  (UPDATE: The Koso DB-01R has ACTIVE HIGH indicators)

For information about how I wired up my Motogadgets Classic speedo, refer to http://k75retro.blogspot.ca/2013/09/k75-re-wiring.html.

gringoloco wrote:Actually could I just connect the alternator cable to the oil temp light on the new gauge? Wouldn't that do the same thing?

Ah, to what purpose are you putting the oil temp indicator on the gauge? There is no oil temp sensor on the K100; there is an oil pressure sensor. The oil pressure sensor has two states -- either open circuit or grounded. There's no 12V supply of electricity coming from that sensor (if you are referring to it; I'm making an assumption here which could be wrong).

You can connect the alternator exciter circuit to any source of switched 12V on the bike. With the proper resistors in place, it will only draw 250mA of current.

Ok great, thank you so much, very useful info!

I'll see what kind of relays I can find and where I can fit them and report back.

I was referring to the oil light on the Koso gauge but since I probably don't have enough information, I'll just connect it to the power with the resistors you mentioned before.

When I connected the high beam light, it only worked when I turned the switch downwards (flash to pass), when I click the highbeam on normally, the light doesn't come on. Any idea what that could be?

If you have the right hand European switch cluster with the off-parking-on switch, your problem may be inside that assembly. You may have a poor connection in the that switch and need to service it.  If that isn't the problem, the left hand switch cluster is also possibly dirty and needs servicing.

Instructions for servicing are here:  http://technik.flyingbrick.de/images/f/f9/61_lenker_rechts.pdf  (in German)

Good discussion as to the reasons why your problem has appeared:  https://www.k100-forum.com/t7683-headlights-not-working-but-pass-light-ok.   Consider installing an Eastern Beaver relay kit to increase the life of your light switch.

If you have low beam, the problem is in the LHS switch assy (which usually is the problem source, when this problem occurs)

My light stopped working half a year ago, so I changed the left switch with a brand new one. Not likely it would go bad in the first 10,000km (I rode a lot this summer).

The headlight isn't actually connected right now though, it was just on the first check to see if the gauge light works that I noticed this.

What's the size of bulb you are using? 60/55?