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I restored and rewired this R26 25 years ago and have had very few problems since the last few months:- Headlight comes on in the Ignition on switch position and battery draining, though the dynamo does seem to be charging (Headllights get brighter at higher revs and voltage at the battery increases up to about 7 volts). I've replaced the bushes and cleaned all the points in the regulator. Charged the battery (many times) but the problem persists. I suspect it is the headlight switch but is does seem to 'click' correctly to all positions and there are no visible loose wires....also the red charging indicator light stays on...so I'm confused and would welcome any suggestions from fellow sufferers!

You might consider getting Ver 2.0 of the Doug Rinckes book on /2 Electrics. For charging system failures where the lamp will not go out, it says the possible causes are:

- brushes are not running smoothly on the slip rings
- slip rings are greasy or oily
- voltage regulator has dirty contacts
- generator armature winding is faulty

On other BMWs, especially the /5-on bikes, there are very critical wiring attachments where the absence of a fiber washer will create the situation you describe. By not be isolated properly from ground, the charge light will illuminate.

It is my understanding that the light comes on when the difference between the battery and the generator output are not equally. The difference causes current to flow and the light comes on.

Kurt in S.A.

Thank you - I have checked brushes run smoothly, Voltage regulator contacts are clean. I don't know what the slip rings are? but the dynamo area is clean and grease free (apart from the cam pad)
I find it hard to believe the armature wiring is faulty as there is a good charge, bike runs fine but the charge light stays on and as the revs build up the headlight comes on too ! - this in the central switch position.
Changed the points recently (Condenser, Coil and spring connections are linked but the attachment post insulated from the points body and the spark is fine.
Is there a good wiring diagram in Doug Rinkes book? - I've got the factory wiring diagram but it doesn't show the points/coil connection. There are many sites that have colour wiring diagrams for sale but I suspect they are all the factory diagrams which is more of a schematic.....so still stuck on this one??

I thought the latest Rinckes book was worth it...there is a free on-line version but it is only for the twins. The new book covers the R25 thru the R69S/US. It has color diagrams for each series.

Slip rings are the term people use on the /5-on bikes for alternators...I guess on generators they're called commutators? It's what the brushes ride on.

Kurt in S.A.

Thank you - yes - cleaned out the commutator and completed the handbook dynamo tests which show it is all OK and the running lights brighten when the revs increase, and the voltage at the battery increases with speed...but after 3 days working on this I'm ready for a rest !..as a bonus I've serviced just about everything.
There is continuity between the segments of the commutator - I suppose as the gaps are clear this is some sort of feedback through the connectors, but the dynamo does work fine according to the handbook tests.
So now I have an R26 that works fine but the ignition light and neutral lights go out as soon as the revs increase and this co-incides with the headlight powering up.......I hope this problem just goes away - I'm out of ideas...
Thanks again for the help.

What is the health of the battery? Have you had it load tested? Just because there's a solid voltage at the battery, that doesn't necessarily mean that the battery is accepting it or acting the way it should. That said, the R26 is a battery-coil ignition setup, so if the battery is too far gone, the bike won't even run.

Kurt in S.A.

Thank you Kurt - New battery about 6 months ago - and I've substituted another good battery to check ....all OK
Just redone the points (again !) runs fine but charging light still goes out as the revs rise and the headlight comes on - all by itself !!
I wonder if there is a fault at the headlamp switch - looked at it a few times and it seems to be fine BUT......
This one has me really foxed!

All of your work is in the wrong area for starting out. Go directly to the headlight switch and you will most likely find it there. My website has photos of the switch parts. w6rec.com Just use Google to find the article.

Thank you for helping Duane - I have read many of your articles with admiration. I have been looking with some suspicion at the switch for some time now with a little reluctance to bend out the tags that hold it in the headlight
It does appear to click positively (if reluctantly !) to the three positions - I can see it connecting.
The wiring looks to be OK - nothing loose and contacts tightened
The Point contact is clean and touches when the key is pressed down (But the key is a little stiff to press down at times)
When I start the motorcycle (works first kick) it ticks over nicely in the ignition position with the red light on then quite suddenly as I increase the revs the headlight comes on.
So it may well be something I can't see and will have to remove the switch....any idea what I should look for if it is not obvious?
I'm off to your website now to look at the photos.....Thanks again ....

Be very careful bending the tangs if you head down that road. It wasn't designed to be a very user friendly kind of thing. Excessive bending, and it might only be once or twice, can create work hardening which means they will end up breaking off. The area needs to be annealed to return its ductility. There are ways to do this, some which can have disastrous effects on the local paint.

Kurt in S.A.