Author Topic: Circuit Modules to Augment Installation of Aftermarket Instruments on K-bikes  (Read 47865 times)

Offline RedBrick

  • Curious
  • Posts: 2
Re: Circuit Modules to Augment Installation of Aftermarket Instruments on K-bikes
« Reply #100 on: November 07, 2018, 06:19:52 AM »
Hello from Finland! RBM, I would like to purchase one of these circuit boards! I have sent you an email to the address I found from the back cover of the manual. I am browsing this site with my mobile phone, I just could not sen PM, that is why the email.
I hope these circuits are still possible to buy, it would save a lot of time and scratching my head trying to solve problems!
  • South Carelia
  • K100 1984

Offline billy

  • Curious
  • Posts: 3
Re: Circuit Modules to Augment Installation of Aftermarket Instruments on K-bikes
« Reply #101 on: November 08, 2018, 04:15:53 AM »
also look at Cafe4racer german guys have developed Bep v3
its a staight plug in to the harnes that goes to the old Speedo
  • Hampshire
  • K100LT R1200GSlc

Offline Laitch

  • ^ Quintessential Motobricker
  • Posts: 6700
Re: Circuit Modules to Augment Installation of Aftermarket Instruments on K-bikes
« Reply #102 on: November 08, 2018, 10:20:14 AM »
also look at Cafe4racer german guys have developed Bep v3
its a staight plug in to the harnes that goes to the old Speedo
You posted once that you were converting to an aftermarket speedometer, billy. Have you had experience using the BEP? How well did the conversion go?
  • Along the Ridley in Vermont.
  • 1995 K75T 72,000 miles
I wept because I had no radials until I met a man who had no splines.
http://www.motobrick.com/index.php/topic,296.msg53303.html#msg53303

Offline sgriffin

  • Curious
  • Posts: 4
Hello All. New member, first post.

I am working on rebuilding a 1994 K75. The bike has <13k and is immaculate so its almost a shame to take it apart but I want it to a bit more interesting.  I have been reading about RBM's TGPI board as well as the BEP 3.0 solution.

My goal with instrumentation is to retain as much of the factory dash functionality as possible as well as other K75 logic i.e. start enable on neutral, charging circuit, indicator cancel, and fuel level or warning.

As far as the gauge goes, I'm thinking about the new Koso TNT-04 or the Acewell ca085.  I'm not sure which one is a better integration.  I have read the Motogadget units integrate well but they are quite a bit more costly.

My strong preference between the two circuit options is to use the board RBM produces. He provides a huge amount information to that end on this forum and that is admirable. And that user manual is crazy good.

So, RBM if you see this please let me know if you are interested in selling yet another circuit board.
  • Dallas, TX
  • 1994 K75,1995 K75RT (1979 R65,1988 R100RS)

Offline rbm

  • ^ Quintessential Motobricker
  • Posts: 1941
Any aftermarket gauge will integrate with my TGPI board or the BEP 3.0 for that matter.  Both of our solutions (mine and Maru's) complement the features available on the vast majority of aftermarket gauges rather than replace them.

My TGPI board is similar to the BEP 3.0.  The BEP has differences over my board.  For example it does all the things my board does except output the gear number on a 7-segment display.  The BEP can only output to a discrete display.  The BEP has additional features over and above what I can offer such as interface for charging light, most of the indicators are brought out from the OEM cluster, and it can work with the old fuel level sender.  My board does not do these things.  Having said that, it is simple to wire up indicators to the OEM harness, including the charging circuit, without help from my TGPI board.  I had specific goals in mind when I designed my board, the same as Maru.  My primary design objective was to offer the most useful functions within a given board size. Maru's goals were more ambitious than mine.

Both of those gauges you link to are not compatible with the discrete outputs from either the BEP or the TGPI for displaying gears.  The Koso TNT has calculated gearing, and the Acewell has nothing.  Both of these gauges are compatible with the single 7-segment display function of my TGPI but you'd have to design an enclosure for the separate display module.  The Motogadget gauges are awesome but they aren't easier or harder to integrate.  They are very high quality but you pay for what you get.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline sgriffin

  • Curious
  • Posts: 4
Thanks for the information Robert. You have given me some great information to consider. I do not at all like the calculated gear idea from Koso. I downloaded their manual and see there is no provision for making this connection.  If calculated by mph, terrible idea. If by monitoring engine rpm delta I can imagine a possibility of some success. I'm going to take a closer look at the Motogadget gear. 

Just so I am clear on the TGPI board,
(1) gear indication can be done on separate 7 segment display
(2) charging circuit connects directly to the gauge or separate indicator. My understanding is the logic of the charging circuit detects lamp illumination by maybe resistance to know when to charge??  and
(3) no solution for reading the old fuel level sender?

Needless to say, I need to think about what my priorities are. There may need to be some compromises and allowances compared to the stock indications.  In the beginning, I thought this would be rather simple but after much research I have realized I have yet to see an example for inspiration where I thought "this is it". 

Thanks again for your input.


  • Dallas, TX
  • 1994 K75,1995 K75RT (1979 R65,1988 R100RS)

Offline sgriffin

  • Curious
  • Posts: 4
I found answer to #3 fuel sender operation on K100-forum.  http://www.k100-forum.com/t9265-messing-with-the-in-tank-fuel-sender
  • Dallas, TX
  • 1994 K75,1995 K75RT (1979 R65,1988 R100RS)

Offline rbm

  • ^ Quintessential Motobricker
  • Posts: 1941
Just so I am clear on the TGPI board,
(1) gear indication can be done on separate 7 segment display
Yes, correct.

(2) charging circuit connects directly to the gauge or separate indicator. My understanding is the logic of the charging circuit detects lamp illumination by maybe resistance to know when to charge??  and
The alternator field winding coils can/will connect through a LED indicator on your gauge if you desire to have a visual indicator of charge.  Some builders choose to forego the indicator and use a resistor in place of the indicator.  In any case, a resistance of some sort is needed in the field coil exciter circuit, be it a LED, bulb or resistor.  This limits current. What current?  The current from the battery that energises (excites) the field coils of the alternator to get the whole charging process started.  What causes the light to illuminate?  The difference in potential between the battery terminal and the regulator output. When the engine RPMs are low, the regulator output is below the terminal voltage of the battery and the LED lights up.  When the engine RPMs raise and the regulator output voltage increases to or above the battery terminal voltage, the LED extinguishes.

(3) no solution for reading the old fuel level sender?

You thought:  I found answer to #3 fuel sender operation on K100-forum.  http://www.k100-forum.com/t9265-messing-with-the-in-tank-fuel-sender  would work with the old sender, but it won't.  I presume with the "old sender" you mean the one with thermisters. If so, the following will work apparently. 
http://www.k100-forum.com/t13947-install-acewell-2853-cluster-in-bmw-k100-1984#165196
http://www.motobrick.com/index.php/topic,11953.msg104846.html#msg104846
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline sgriffin

  • Curious
  • Posts: 4
Thanks very much Robert. I understand your explanation of the charging circuit.  My bike is a 94 K75 so I believe it has the "new" float style fuel sender.  Parts diagram appears that way. 

My #3 statement was confusing by saying "old" fuel sender.  I had that on my mind after reading your opening discussion on the topic that the BEP can work with the old one. Not sure if BEP works with the "new" float style throught the OEM harness but from your other forum discussion 180 flip does the trick.

One a separate note, I found what I thought was an interesting variation of the Acewell CA85.  This one available from Acewell UK site offers BMW style scale and options for machine bezel and sleeve.  This may be widely know on the forum but was new to me so I'm sharing for anyone interested in maintaining a BMW look for their instrumentation.
  • Dallas, TX
  • 1994 K75,1995 K75RT (1979 R65,1988 R100RS)

Offline rbm

  • ^ Quintessential Motobricker
  • Posts: 1941
The BEP 3.0 does not work with the '86+ fuel level sender because that sender does not connect up through the OEM gauge cluster connector. The BEP 3.0 does work with the '83 - '85 thermistor based fuel level sender because that sender does interface directly through the OEM gauge cluster connector.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline zonex

  • Motobrick Curious
  • Posts: 12
Good morning RBM, any of your TGPI units ready to go?
$75 Canadian plus shipping is still the price? shouldn't be too much as I'm down the 401 in Windsor
  • Windsor Ontario
  • 1985 BMW K100

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