Forum bmwbike.com

For the third time in three months and 500 miles, my R27 generator has lost its polarity.

When this happens, the generator light glows bright red at idle, then pulses from dark to bright as the revolutions increase, until the light flashes so fast it appears as a steady red.

The solution is always to take a 3-foot length of thick insulated house wire, jam one end under the B+ terminal of the battery, and firmly touch the other end of the wire to the D+ (blue wire) terminal of the generator. I now carry such a wire in the bike's tool box.

This R27 was restored in 1999. The generator pole housing (the whole outer part) is new from Huggett two years ago, and the rotor is new from Huggett a year ago. I have two NOS mechanical regulators that I
swap back and forth to be sure that the problem is not in the regulator.

This happened to another R27 owner so much that he ran two wires to a button that he could push to repolarize the generator while he was riding. He finally replaced the generator with a 12v alternator.

I would like to know why the generator must be re-polarized so much. One expert says he thinks the R27 engine, being mounted in rubber, is
poorly grounded. There appears to be no dedicated ground for the engine. He suggested that I run a new wire between a transmission bolt and the negative terminal of the battery.

However, I had a new R27 in 1966 and rode 18,000 miles in two years without any generator trouble, so I don't see how this extra wire will make a difference.

Any ideas?

After repolarizing the generator today, the red light went out for a few minutes, until I came to the first stop sign. Someone has suggested that both of my two NOS mechanical voltage regulators are bad, so I am going to order the new electronic regulator offered in the store here (12 32 8 008 106.1).

Hey Allan,
I was afraid that you will have this problem again.
It looses polarization when the engine has only low rpm? How low?
You wrote that you have bought a new (?) generator housing, really new or good but used?
What`s about earth on your Z-Regulator (its a Z, isn`t it?), this depolarizing is normally bad earth (especially on the regulator), check this first.
Then take a llook to the brushes, all tight? especially the wire inside the coal(?) brushes.
You wrote also that a electronic is twice as expensive as a normal Regulator? Normaly the Z-Regler cost about 300 Euros and a electronic 50 Euros.
If this all was (what I write above) is ok, write again, there could be a few other things which are not correct, but...step for step.
I have this problem several years ago (Gosh, more than 20, time runs)on my 25/3 sidecar and Bosch also couln`t find the reason. I found it after 1,5 years .
Greetings
Rolf Gehrke

Yes, the un-polarization seems to occur at low rpm, at the first stop sign that I come to after leaving my driveway.

My rotor and stator are new exchanges from Huggett.

Another person suggested the rubber mounted engine caused poor grounding of the generator, and suggested that I run a wire from a transmission bolt to the battery (-). I doubted that idea.

Your suggestion is that the regulator is poorly grounded, and I suppose that is possible. I will check the connections at the present mechanical regulator when the new electronic regulator arrives and I remove the tank.

I found the same part number at Bench Mark Works in the US, it is probably the exact same item, and the price is the same when shipping is compared. So I bought from Bench Mark Works.

I have received an electronic regulator from Bench Mark Works, which I believe is the same as Huggett sells, made by Elektronic-Data Kleiber GmbH.

In 1999 I bought an electronic regulator from Bobs BMW and it consisted of a small 1-inch section of aluminum tubing filled with epoxy in which the electronics were imbedded. It had spade-type termnals that required new terminations on the original wires, and being so smalll, the unit only mounted in one of the original holes. I did not like the looks of it and re-sold it.

In comparison, the Kleiber electronic regulator from Bench Mark Works and Huggett is impressive. The case and mounting tabs are the same size as the original mechanical regulator, and the whole thing is machined from one solid block of aluminum. One side of the case is open to receive the electronic components, which are imbedded under solid black epoxy. From the epoxy emerge three regular screw-type terminals. Engravings on the case identify them as 30/51 B+, DF, and 61 D+ to correspond with the wires from the generator. It is a high quality item.