Wiring Harness Question - 1979 R65 - US Spec

[Eric65123]

This'll be my first post for a long while being a lurker. So be please be patient with me guys 

I am currently tracing and checking all my wiring. I have traced almost all of it and re-spliced(replaced) burnt and almost melted ones.

I found 2 separate diodes (not the diode board) which I am trying to identify from the wiring diagram by Clymer. I have figured out one of them which is the diode  coming from the clutch switch and starter relay (circled in yellow-green) but I can't seem to figure out what is that diode circled in red in the photo from the diagram.

Will it look the one I attached? or is this within the circuit board of the tachometer or what? Not sure what I am talking about here.

Please shed some light in this confusion R65 gurus. because I have one diode that I can't find in the wiring diagram.

Thanks a lot guys!

[mrclubike]

The diode circled in red is a diode it is your Tachometer

Clymer must have got it  labeled wrong because of a bad translation

If your follow the wires coming out of it
You will find
One is a battery positive switched
One is Ground and the other one is your Tach signal from the coil

The factory wiring diagrams are a lot better
I think Snobum may have one on his site

[Bob_Roller]

From the looks of the wiring diagram, this is for a first generation R65, '79-'80 model year bikes .

Notice the two single ignition coils, condenser and contact breaker points .

The diode is a red LED on the face of the tachometer , it illuminated when you got the rpm's at or near redline .

[Barry]

Here is a very high resolution wiring diagram for the 78-80 model. It's a PDF so you can zoom in to it for ever and it remains crystal clear. I have it printed out A3 for easy reference. The yellow diode will be the one in the starter inhibit circuit which requires either neutral to be selected or the clutch pulled in before the starter will engage.

Also attached a translation of the legend.

[Barry]

Can't do two attachments on one post so here is the legend.

[georgesgiralt]

Here is the BMW factory schematic for an European bike. I bet there are not so much difference.

[mrclubike]

This is where the confusion come from when Clymers translated the Diagram

[mrclubike]

FYI everyone
The other diode circled in green was moved inside the starter relay on the later R65
It is possible to install a standard relay without the built in diode and then add the diode in the wiring like the early R65
I am going to do this when I get a chance 

[Barry]

Just to confuse the issue my 79 R45 doesn't have the over rev led. Not that I miss it but can you believe they made a tach for the R65 with the LED and a tach for the R45 without it.

[georgesgiralt]

Barry, I  think that your R45 either had the tacho replaced at some point or that you have the post 81 tacho prototype ....

[Tony Smith]

I had to replace the starter inhibit diode in the wife's R65/80  a couple of years ago. I baulked at the absurd BMW price and made my own using a 20c diode form the local electronics place and two crimp terminals. ?in the interest of not having to do the job twice I removed the plastic from the crimp terminals and soldered the diode between them. i then slipped a piece of heat shrink tubing over it and hit it with the heat gun.

[Barry]

I had to replace the starter inhibit diode in the wife's R65/80  a couple of years ago. I baulked at the absurd BMW price and made my own using a 20c diode form the local electronics place and two crimp terminals. ?in the interest of not having to do the job twice I removed the plastic from the crimp terminals and soldered the diode between them. i then slipped a piece of heat shrink tubing over it and hit it with the heat gun.

That's what I'd do. Not about to pay £7.50 for a basic  diode that costs a few pence and that I already have anyway.

[Tony Smith]

Crappy photo - but is good enough to show what needs to be done. I give you my 35c BMW diode replacement (i'm allowing 5 cents for the terminals).

[Eric65123]

Happy New Year everyone!

Firstly, want to say thank you to everyone who chipped in to this thread and now I will try to revive this after almost a year. Yes, been hiding in a cave for that long!

I have worked out the diode circled in green, figured that my wiring has been botched by previous owner. Redid that part as per the diagrams Barry have sent--Thanks Barry!

I copied Tony's practical diode recipe and my starting system is now working as original.

Now I got this new tachometer, the generic ones from ebay, https://www.amazon.com/Ambuker-Speedometer-Tachometer-Odometer-Motorcycle/dp/B06XKMDWZQ/ref=pd_day0_263_4?_encoding=UTF8&pd_rd_i=B06XKMDWZQ&pd_rd_r=MCRD7MSWVAH0GCWHTTYV&pd_rd_w=zl4e4&pd_rd_wg=ZgTNN&psc=1&refRID=MCRD7MSWVAH0GCWHTTYV and adapted it to the harness.

All is working except for the RPM. The gauge is asking for a positive connection + from the coil or the rectifier.

Now if I understand correctly, the black wire from the coil originally connected to the original RPM gauge is a negative wire. - Do i just move this RPM black wire in the ignition coil and connect it to the other side (+) of the coil? Tried this but not working.

Any thoughts airhead gods?

[mrclubike]

All is working except for the RPM. The gauge is asking for a positive connection + from the coil or the rectifier.

Now if I understand correctly, the black wire from the coil originally connected to the original RPM gauge is a negative wire. - Do i just move this RPM black wire in the ignition coil and connect it to the other side (+) of the coil? Tried this but not working.

Any thoughts airhead gods?

No

The black wire you speak of is not a true "Negative" or "Earthing"  wire
Those wires are always brown on a BMW
It is the rpm signal from your ignition system
It switches from positive to negative as the points open and close

Their should be a Tach signal wire on the back of your new Tach that the black wire needs to hook to

Looking at the print in your link it appears to be the BLK/PUR wire on the 9 pin connector

But I could be wrong because the Chinese to Enlgish trans is not real clear