R26 electrical problem

Single & twin cylinder model BMW Airhead specific discussions
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Lpalfa
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R26 electrical problem

Post by Lpalfa » Sat Aug 09, 2014 8:56 am

I have restored a 1958 r26 over the winter. The idea was to maintain originality and it came out great. I have ridden it about 200 miles and runs great. However it does have an electrical issue which I hope the forum can help me with.
These bikes had no fuse but I installed a 15 amp fuse on the positive side of the battery. The bike starts fine and runs great but the fuse blows, not immediately but maybe 15 minutes into the ride. I replace the fuse and it will start right up and on my way again. Everything works fine including turn signals etc. I have checked over the entire wiring but cannot find anything that could cause this. I do not think its a dead short and the fuse doesn't blow when I operate any of the loads such as lights, horn, signals etc. It is still the 6volt system.
Should the fuse be installed on the positive side or would the negative be better. Also is 15 amps enough for these bikes. I know the bike starts on the battery then once operating the generator takes over. Would this put extra load on this fuse I'm not aware of? I haven't tried higher amp fuses yet. I'm concerned if it is a short it may start melting wires.

Any help would be appreciated.

Lawrence

Duane Ausherman
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Re: R26 electrical problem

Post by Duane Ausherman » Sat Aug 09, 2014 11:35 am

I think that 15 amps is plenty. Have you tried the slo-blo fuses?

If the fuse is mounted right at the battery, the current flow is equal in both sides. That is assuming that the positive side has only one wire and that is the fuse holder.

I am concerned that the fuse blows because you have an intermittent short somewhere. It can be very hard to find them too. That is one of the most difficult electrical problems to find.
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Major Softie
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Re: R26 electrical problem

Post by Major Softie » Sun Aug 10, 2014 12:27 am

IF you have a stock generator, it's only supposed to be putting out 60W max, so that's only 10A. The 15A fuse should be fine. Duane's suggestion for trying a slo-blow is a good one, but I suspect there really is something wrong.
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Lpalfa
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Re: R26 electrical problem

Post by Lpalfa » Fri Aug 15, 2014 6:07 pm

I have the bmw workshop manual trying to troubleshoot this charging system. Hope I can work through it with you to fix it. So far I have used my digital meter at the battery and at 2500 rpm, no charge, actually voltage went from 6.45 at no running to 6.25 running but that's probably normal load. Then according to the manual, I put my meter on terminal +61 at the generator and ground, started the bike and at 2500 to 3000 rpm disconnected the ground from the battery. Engined died. Manual said it should read 7.2 - 7.9 v.
When the bike was running and I was using it, I did not check that the system was working but the generator light was out and over a few months time, the battery seemed to stay charged. However I did not see the headlight brighten up with revs. I thought it was because of the electronic regulator. One indicator that I think it was charging was my turn indicators. If the lights were on at idle the indicators did not flash but when I raised the rpm, they worked.
Some history, I purchased this bike with a twelve volt system and I wanted to restore to original. I bought a rebuilt 6v generator, regulator and coil complete from Uli in Germany who indicated it was fully tested.

I have removed the. Stator and armature from the bike looking for any defects. I also tested the armature for any shorts. There doesn't seem to be any shorts to ground. Not sure what other tests I can do on the armature to see that it is good. Any help going forward would be appreciated. Does anyone have a diagram on how the electronic regulator is wired in and how do you test it. Not sure what to do next.

Lawrence

Duane Ausherman
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Re: R26 electrical problem

Post by Duane Ausherman » Sat Aug 16, 2014 2:48 pm

Do you have the BMW electrical book. I forget who wrote it, but it is excellent. The BMW stuff is very poorly done. Those manuals were never intended for the average owner. They were written for the quite capable mechanic that had been to the official BMW tech schools.
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Kurt in S.A.
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Re: R26 electrical problem

Post by Kurt in S.A. » Sat Aug 16, 2014 4:46 pm

Duane Ausherman wrote:Do you have the BMW electrical book. I forget who wrote it, but it is excellent.
Probably Don Rinckes. Version 1 is out on the web for free download...more specifically covers the twins. Vech sells Version 2 which is much better, has color diagrams, and adds in the single cylinder bikes.

Kurt in S.A.

Garnet
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Re: R26 electrical problem

Post by Garnet » Sun Aug 17, 2014 1:58 am

What type of fuse are you using , glass, ceramic, or ATO?
My R26 will vibrate the filaments out of taillight bulbs on a regular basis, and I'm sure would do the same to a glass fuse. I use an ATO fuse on the positive side, but I run a Power Dynamo 12v system which is quite different.

The stock system used no fuse, but it's not a bad idea to add one to save the chance of melting wires and your electronic v/reg.
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Duane Ausherman
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Re: R26 electrical problem

Post by Duane Ausherman » Sun Aug 17, 2014 2:28 am

Kurt in S.A. wrote:
Duane Ausherman wrote:Do you have the BMW electrical book. I forget who wrote it, but it is excellent.
Probably Don Rinckes. Version 1 is out on the web for free download...more specifically covers the twins. Vech sells Version 2 which is much better, has color diagrams, and adds in the single cylinder bikes.

Kurt in S.A.
Yep, that is the book. Get it.
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Garnet
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Re: R26 electrical problem

Post by Garnet » Sun Aug 17, 2014 10:17 am

I just looked through my stuff and it seems that the info I had on electronic regs did not survive the last cull of paperwork. :oops:


Have you tried posting your question here: http://bmw-einzylinder.de/forum/index.p ... &board=6.0 They have an English section and really know what they're talking about.

Edit: Here is a link to the wiring diagram for the E v/reg. You need to register as a member to see the links.
http://bmw-einzylinder.de/forum/index.php?topic=10345.0

Edit again: Here is a link to a thread on a very similar problem that I had: http://bmw-einzylinder.de/forum/index.php?topic=2893.0
Garnet

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