R90S Junction Board Diode

I have been working on my R90S, which has been idle since 1997. I have a starting circuit fault which i traced to the diode on the back of the circuit junction board in the head lamp bucket. Diode failed in open mode and I am looking at replacing it. I do not want to pull all of the wires off and take the board out, so I am thinking about just piggybacking a replacement diode in there. Just wanted to hear what others have done.

With the clearance you have behind the headlight I don’t think that would work. I have had the diode go on my 75 R90/6. When I bought it in 85 the previous owner didn’t replace the clutch switch and the neutral switch was not working right. By not having these I relocated one of the wires to bypass the diode. A few years ago do to me pinching a wire I smoke my harness and place this and the board with a used good one I had and the neutral switch. Couple years later the diode went and relocated the wire again. With out looking at wire diagram I noticed wasn’t need when the clutch and neutral switch’s are not in the system. And just relocating the one wire that is on the bad side of the of the diode. If I ever restore this bike I will go back to normal wiring.

Well, most Radio Shack stores are gone and Photobucket killed all the pictures, but maybe this will help anyway:
CLICK HERE

swall said:

I have been working on my R90S, which has been idle since 1997. I have a starting circuit fault which i traced to the diode on the back of the circuit junction board in the head lamp bucket. Diode failed in open mode and I am looking at replacing it. I do not want to pull all of the wires off and take the board out, so I am thinking about just piggybacking a replacement diode in there. Just wanted to hear what others have done.

Click to expand...

Hi Swall,

You can replace the diode without removing the junction board, but you have to loosen the board so you can snip out the old damaged one. You can loosen the mounting screws to tip the board up. Snip the leads to the bad diode and remove it. Then install a replacement diode IN THE SAME ORIENTATION on the front of the board using the two terminals on the front the old diode was soldered to. Insulate the leads with shrink tubing to prevent accidental shorts of the exposed leads.

Bob Fleischer (aka, snowbum) has published details about the diode, what to get to replace it, in this write up. It's all in a black bordered box of text about 1/3 of the way down the page. The section of what type of diode to look for is about 45% of the way down the page, still inside the black bordered box.

--> http://bmwmotorcycletech.info/electricalhints.htm

Hope this helps.

Best.
Brook Reams.

Thank you. That was good info.