Diode board replacement

I need to replace my 1973 R60/5's diode board. There are a number of them for sale through eBay from salvage companies but I am wondering how do you know it will work? Euroelectric has a diode board replacement but it doesn't list the Bosch part number on it. Can anyone recommend a source for diode boards?
Thanks ,
Debbie

wilddeb said:

I need to replace my 1973 R60/5's diode board. There are a number of them for sale through eBay from salvage companies but I am wondering how do you know it will work? Euroelectric has a diode board replacement but it doesn't list the Bosch part number on it. Can anyone recommend a source for diode boards?
Thanks ,
Debbie

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Rick Jones at Motorrad Elektrik.

The phrase 'caveat emptor' (buyer beware) comes to mind when buying used electrical parts. Bite the bullet and buy new if you can. As Mr. Glaves says Rick Jones is an excellent source. I have also bought a Thunderchild diode board and am quite happy with the part and service.

If I were needing a diode board I would get a Thunderchild or Omega board. If you do end up using a bosch diode board (OEM), I would take some steps to ensure a good ground. The most effective grounding method that I've seen was performed on a buddy's bike at the 98 CASS Rally in WVa. This modification was done by someone having a shop somewhere in WV (don't recall where or who) and the demonstration was done on a rainy Saturday under a covered picnic area. My buddy's bike had the charging light come on while we were enroute to the rally and investigation at the rally showed his diode board as failed. [The board had corrosion about the brass mount points and it was apparent by the melted solder that his board had gotten quite hot.] Fortunately, someone at the rally had a spare diode board to "loan" to my buddy.

Attached is a photo showing the addition of the supplemental ground wire and another photo showing how the supplemental wire was attached to the bike. Links for Thunderchild and Omega diode boards follow -

http://www.thunderchild-design.com/homepage.html

http://www.motoelekt.com/charging.htm

wilddeb said:

I need to replace my 1973 R60/5's diode board. There are a number of them for sale through eBay from salvage companies but I am wondering how do you know it will work? Euroelectric has a diode board replacement but it doesn't list the Bosch part number on it. Can anyone recommend a source for diode boards?
Thanks ,
Debbie

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i would not go used unless you want to test it and fix it if there is something wrong with it.

i /would/ get the metal diode board mounts. when i replaced mine with the EME diode board (beemershop) one of the rubber mounts had failed and one of the others were going as well. i would also get the diode board and the mounts lined up and in place before getting the bolts on the mounts. if you bolt up one or two mounts you may have a hard time getting the board to sit right (or risk breaking it). also, one of those little finger magnet deals would be great to have when doing this job.

i am super curious if the gurus think that adding a second diode board ground is also a good idea if you go to metal diode board mounts.

- jon

btw, i got a bmw electrics book and starter from rick and couldn't be happier

hotwheels22 said:

i am super curious if the gurus think that adding a second diode board ground is also a good idea if you go to metal diode board mounts.

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Couldn't hurt. It was recommended by BMW in a service bulletin.

20774 said:

Couldn't hurt. It was recommended by BMW in a service bulletin.

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hi kurt,

a ton of thanks. I have not seen much by way of explanations on how to do this. basically I am taking one of the top (?) two retaining bolts that already have ground and putting a third ground somewhere on the timing chain cover?

do I drill a hole and just get a nut and washer and bolt and use some blue loctite? or is there a suggested location for this?
or maybe just open it up and use common sense...?

THANKS

jon

20774 said:

Couldn't hurt. It was recommended by BMW in a service bulletin.

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That bulletin applied to R100s that came with rubber mounts. BMW produced a harness to complete the procedure. Diode board grounding was only ever a problem on R100s with rubber mounts and only R100s ever came with rubber mounts, but like the secret passed around a circle, over the years the topic has expanded beyond reality.

lkchris said:

That bulletin applied to R100s that came with rubber mounts. BMW produced a harness to complete the procedure. Diode board grounding was only ever a problem on R100s with rubber mounts and only R100s ever came with rubber mounts, but like the secret passed around a circle, over the years the topic has expanded beyond reality.

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Unless there ends up being corrosion on the existing metal mounts. Again, it wouldn't hurt to provide an extra path to ground.

hotwheels22 said:

do I drill a hole and just get a nut and washer and bolt and use some blue loctite? or is there a suggested location for this?
or maybe just open it up and use common sense...?

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Snowbum discusses this on this page, about 2/3 the way down:

http://bmwmotorcycletech.info/diodebds&grdgwires.htm

One of the mount locations is shown in a picture above. It's been a while since I installed mine but one of the other ends goes to one of the diode board mounts. I bought a harness ready to install from Rick at Motorrad Elektrik. They're easy enough to make, but I was buying metal mounts from him anyway.

wilddeb said:

I need to replace my 1973 R60/5's diode board. There are a number of them for sale through eBay from salvage companies but I am wondering how do you know it will work? Euroelectric has a diode board replacement but it doesn't list the Bosch part number on it. Can anyone recommend a source for diode boards?
Thanks ,
Debbie

Click to expand...

I would use this one: http://www.euromotoelectrics.com/BMW-R-Airhead-Heavy-Duty-Diode-Board-p/boalt-rect063edl.htm
Half the price of a new BMW OEM and a better design.

And a set of these: http://www.euromotoelectrics.com/BMW-R-Airhead-Heavy-Duty-Diode-Board-p/boalt-rect063edl.htm

The heavy duty version of the diode board is 3 bucks less than the Bosch style replacement and comes with a new wiring harness with heavier guage wire. A good thing...

The sold metal mounts will insure a good ground. Bad grounding was a weak point in the OEM design and these fix the problem assuming your engine time chest cover is well grounded to the motor itself. Sometimes painted surfaces defeat good grounding so extra ground leads need to be attached. As Snowbum explains in depth, an ohmeter tells the story in very short order.

Emerald Island diode boards have a good reputation and they are pretty heavy duty as well. Rick Jones sells one under the Omega brand that looks exactly like the Emerald Island board for $90 I believe. Another good choice but a tiny bit more pricey. His mounts are more than Euromotoelectic also. We're talking five bucks here so no big deal. Both great suppliers

Rubber Mounts

lkchris said:

That bulletin applied to R100s that came with rubber mounts. BMW produced a harness to complete the procedure. Diode board grounding was only ever a problem on R100s with rubber mounts and only R100s ever came with rubber mounts, but like the secret passed around a circle, over the years the topic has expanded beyond reality.

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Hi lkchris,

A minor quibble with "...and only R100s ever came with rubber mounts, ...". I found them on a 1983 R100RS as well. I replaced them as a matter of course and found one had cracked completely through and the other was about 50% cracked.

Best.
Brook Reams.

brook.reams said:

Hi lkchris,

A minor quibble with "...and only R100s ever came with rubber mounts, ...". I found them on a 1983 R100RS as well. I replaced them as a matter of course and found one had cracked completely through and the other was about 50% cracked.

Best.
Brook Reams.

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I wonder if he meant all the R100 engines as in "all the R100's engines" and not just the R100S model as in just that particular R100 bike. I had them on my RS as well and I've seen them on other R100 engines as well. If I find them on a bike I replace them with solid aluminum mounts along with getting rid of any paint at ground contact points. BMW did not think this through very well and the extra ground wires they used were a band aid fix (which did work) but not a real good solution.

lkchris said:

Diode board grounding was only ever a problem on R100s with rubber mounts and only R100s ever came with rubber mounts.

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After 25 years, one of mine had failed. I chose to replace all four of them but I went with identical mounts from a fastener supply.

As for grounding, owners can have issues with a ground strap or a solid mount if they end up with corrosion on either. Periodic maintenance.